Arctostaphylos – Bearberry Leaf (Uvae ursi folium)
|Latin name of the genus:||Arctostaphylos|
|Latin name of herbal substance:||Uvae ursi folium|
|Botanical name of plant:||Arctostaphylos uva-ursi (l.) spreng.|
|English common name of herbal substance:||Bearberry leaf|
Latin name of the genus: Arctostaphylos
Latin name of herbal substance: Uvae ursi folium
Botanical name of plant: Arctostaphylos uva-ursi (L.) Spreng.
English common name of herbal substance: Bearberry Leaf
1.1. Description of the herbal substance(s), herbal preparation(s) or combinations thereof
Bearberry leaf (Uvae ursi folium) consists of whole or cut, dried leaf of Arctostaphylos
A)Comminuted herbal substance as herbal tea
B)Powdered herbal substance
C)Dry extract (DER 3.5 – 5.5:1), extraction solvent ethanol 60% (V/V) containing 23.5 – 29.3% of hydroquinone derivatives calculated as anhydrous arbutin (spectrophotometry)
D)Dry extract (DER 2.5 – 4.5:1), extraction solvent water containing 20 – 28% of hydroquinone derivatives calculated as anhydrous arbutin (spectrophotometry)
Combinations of herbal substance(s) and/or herbal preparation(s) including a description of vitamin(s) and/or mineral(s) as ingredients of traditional combination herbal medicinal products assessed, where applicable.
Species anticystiticae: Betulae folium 20 parts, Uvae ursi folium 20 parts, Maydis stylus 20 parts, Liquiritiae radix 20 parts, Graminis rhizoma 20 parts (Pharmacopoeia Helvetica V, 1953)
Species anticystiticae: Betulae folium 25 g, Liquiritiae radix 30 g, Uvae ursi folium 45 g (Pharmacopoeia Helvetica VII (1993)
Species urologicae: Uvae ursi folium 35 parts, Herniariae herba 35 parts, Betulae folium 30 parts (Österreichisches Arzneibuch 9, 1960)
Blasen- und Nierentee II: Uvae ursi folium 35 – 50%, Betulae folium 10 – 20%,
Phaseoli fructus sine semine 10 – 20%, Equiseti herba 10 – 30% (Standard Zulassungen, 1996) Blasen- und Nierentee IV: Uvae ursi folium 35 – 50%, Ononidis radix 10 – 25%,
Orthosiphonis folium 15 – 30%, Equiseti herba 10 – 30% (Standard Zulassungen, 1996) Blasen- und Nierentee V: Uvae ursi folium 35 – 50%, Phaseoli fructus sine semine 10 – 20%, Solidaginis or Solidaginis virgaureae herba 10 – 25%, Orthosiphonis folium 15 – 30% (Standard Zulassungen, 1996)
Blasen- und Nierentee VII: Uvae ursi folium 35 – 50%, Betulae folium 15 – 25%, Graminis rhizoma 15 – 25% (Standard Zulassungen, 1996)
Urologicae species: Betulae folium 30 g, Uvae ursi folium 30 g, Herniariae herba 5 g, Menthae piperitae herba 15 g, Ononidis radix 10 g, Petroselini radix 10 g (Slovenský farmaceutický kódex 1, 1997)
Other herbal teas reported by the Member States:
Uvae ursi folium, Juniperi fructus, Betulae folium, Equiseti herba, Solidaginis herba, Orthosiphonis folium (DK)
Uvae ursi folium, Equiseti herba, Myrtilli herba, Matricariae flos, Sambuci flos, Solidaginis herba, Thymi herba (SK, CZ)
Urticae folium, Uvae ursi folium, Betulae folium, Juniperi
Betulae folium, Uvae ursi folium, Ononidis radix, Petroselini radix, Polygoni avicularis herba, Sambuci nigrae flos, Urticae herba, Millefolii herba (CZ)
Betulae folium, Uvae ursi folium, Herniariae herba, Menthae piperitae herba, Ononidis radix, Petroselini radix (CZ)
Other combination products reported by the Member States
Uvae ursi folii extractum 5:1, Taraxaci radicis cum herba extractum 5:1 – tablets (DK, NO)
Uvae ursi extractum, Solidaginis giganteae herbae extractum, Orthosiphonis folii extractum – tablets (DK)
Extract of Solidaginis herba, Betulae folium, Cerasi stipites, Equiseti herba, Uvae ursi folium, extraction solvent ethanol 45% V/V – oral liquid (HU)
Extract of Uvae ursi folium, Urticae radix, Salviae officinalis folium, Betulae folium, Salicis cortex, Millefolii herba, Urticae folium, extraction solvent ethanol 24% V/V – oral liquid (HU)
Extract of Urticae radix, Salviae folium, Uvae ursi folium, Cucurbitae semen, Betulae folium, Salicis cortex, Millefolii herba, Urticae folium, extraction solvent 20% ethanol (DER 1:4.2) – oral liquid (HU)
Extract of Uvae ursi folium, Millefolii herba, Agrimoniae herba, Urticae folium, Equiseti herba, Betulae folium, extraction solvent 20% ethanol (DER 1:4) – tincture (HU)
Overview on main active compounds (Bradley 1992; ESCOP 2003; British Herbal Pharmacopoeia 1996; Gruenwald et al. 2004; Barnes et al. 2002; Frohne 2004; Hänsel et al. 1993; Britton and Haslam 1965; Frohne 1977; Jahodář et al. 1978):
Hydroquinone derivatives: arbutin
The amount of arbutin and methyl arbutin is related to the photometric method with
Polyphenols (tannins): 10 – 20%, gallotannins including
Phenolic acids: approximately 0.25% in free form, mainly gallic,
Flavonoids: hyperoside (0.8 – 1.5%),
Iridoid glucoside: monoterpein (0.025%)
Triterpenes: 0.4 – 0.8%, including ursolic acid, uvaol,
Other constituents: allantoin, resin (e.g. ursone), volatile oil (trace) and wax
1.2. Information about products on the market in the Member States
Powdered herbal substance in solid dosage forms
Marketing authorisation of coated tablets containing 500 mg of the powdered herbal substance in one tablet is reported from Germany (authorised at least since 1976). The posology for adults and adolescents over 12 years is 6 tablets 4 times daily. The product is used for treatment of inflammatory diseases of the urinary tract collection system. The product should not be used longer than one week and not more than 5 times a year without medical advice.
The powdered herbal substance in a form of capsules (1 capsule contains 270 mg of the powdered herbal substance) is registered in Spain (since 1991). The dosage is 1 capsule 3 times daily. The product is used as a diuretic. The use in children is not recommended.
There are hard capsules containing 350 mg of powdered herbal substance registered in France (since 1982). The posology is 2 capsules 2 times daily (up to 5 capsules per day). The product is “traditionally used to promote the renal elimination of water and as an adjuvant to diuretic treatments in benign urinary tract conditions”.
Comminuted herbal substance as herbal tea
Comminuted herbal substance in a form of herbal tea is registered/authorised in Germany, Poland, Spain and Lithuania for more than 30 years, in Slovenia since 1996 and in Estonia since 2005. The tea prepared from 1.5 – 3 g of the comminuted herbal substance and 150 ml of boiling water should be used 3 to 6 times daily. The teas are recommended for the treatment of uncomplicated, mild infections of the lower urinary tract (Poland, Slovenia), for treatment of inflammatory diseases of the urinary tract collection system (Germany, Lithuania) or as a diuretic and urinary tract antiseptic (Spain, Estonia).
Marketing authorisation for tablets containing 500 mg of dry extract (2.5:1), extraction solvent ethanol 50% (V/V) has been reported from Belgium (authorised since 2006). The dosage recommended for adults and adolescents is 2 tablets 4 times daily. The duration of use is limited to 5 days. The product is used as urinary antiseptic in cases of cystitis in adult women not having other health problems and not pregnant.
In Germany, a marketing authorisation for coated tablets containing 238.7 – 297.5 mg of dry extract (3.5 – 5.5:1), extraction solvent ethanol 60% (V/V), corresponding to 70 mg of hydroquinone derivatives calculated as anhydrous hydroquinone has been granted (since at least 1976). The posology is 2 tablets 3 times daily. Other marketing authorisations have been approved (since at least 1976) for 2 products – coated tablets – with a dry extract (3 – 4:1), extraction solvent water. One of them contains 114 – 143 mg of the dry extract corresponding to 31.5 mg of hydroquinone derivatives calculated as anhydrous arbutin and the other 228 – 315 mg of the dry extract corresponding to 63 mg of hydroquinone derivatives. The dosage is 4 times 4 to 5 tablets, respectively 4 times 2 – 3 tablets daily. Additionally marketing authorisation for film coated tablets containing 425.25 – 519.75 mg of dry extract (2.5 – 4.5:1), extraction solvent water corresponding to 105 mg of hydroquinone derivatives has been reported (authorised since at least 1976). The dosage recommended is 2 tablets 2 to 4 times daily.
All above mentioned products are indicated for the treatment of inflammatory diseases of the urinary tract collection system. They are intended for adults and adolescents over 12 years and should be used no longer than one week and not more than 5 times a year without medical advice.
adolescents over 12 years is 4 tablets 3 times daily. The tablets are used in uncomplicated infections of the lower urinary tract, when antibiotic treatment is not considered essential.
In France, hard capsules containing 200 mg of dry extract (3.5 – 6.0:1), extraction solvent water, are registered (since 1992). The posology is 1 capsule twice daily. The product is “traditionally used to promote the renal elimination of water and as an adjuvant to diuretic treatments in benign urinary tract conditions”.
In Germany, an oral liquid medicinal product containing an extract (1:0.54 – 0.99), extraction solvent water: calcium oxide (44:1), is authorised (since 2006). The dosage is 1.8 – 3.6 ml of the product (corresponding to 101 – 207 mg of anhydrous arbutin) 4 times daily. The product is used for supportive treatment of inflammatory diseases of the urinary tract in adults and adolescents over 12 years. The product should be used no longer than one week and not more than 5 times a year without medical advice.
For information on combination products marketed in the MS, see section 1.1.
Regulatory status overview
MA: Marketing Authorisation TRAD: Traditional Use Registration
Other TRAD: Other national Traditional systems of registration
This regulatory overview is not legally binding and does not necessarily reflect the legal status of the products in the MSs concerned.
1.3. Search and assessment methodology
Databases assessed (date, search terms) and other sources used
Data bases PubMed (June 2009) and HSDB were searched using the terms “Uvae ursi”, “Uva ursi”, “bearberry leaf”, “arbutin” and “hydroquinone”. Handbooks and textbooks on the topic were also used.
Articles and data that were found to be relevant for assessment are included in the List of references.
2. Historical data on medicinal use
2.1. Information on period of medicinal use in the Community
Bearberry leaves use is for the first time literally documented in the Middle Ages in the Welsh “Physicians of Nyddfai” from the 13th century. It seems that bearberry leaf was used in Northern areas as a folk remedy long before it came to the Central Europe. In Renaissance herbaria bearberry was only mentioned occasionally without any link to a specified medicinal use. Bearberry is mentioned for example in “Historia Rariorum Plantarum” by Carolus Clusius, Antwerp (1601) and also by Linné in his “Materia Medica” from 1749. In Germany, bearberry was used in larger scale since the middle of
18th century. From the beginning of 19th century, bearberry is in official use. It was used for treatment of different diseases such as hydrops, lithiasis, in diabetes, for the therapy of gonorrhoea, etc. Until now only the use as urinary tract antiseptic and diuretic remains. Bearberry leaf was used also in the “New World” by the North American Indians for the treatment of urinary tract diseases (Frohne 1977).
The medicinal use has been documented continuously in many pharmacopoeias, pharmacognostical texts and handbooks dating e.g. from 1926, 1938, 1947, 1953, 1960, 1977, 1986, 1998, 2002, 2003 and 2009 – Deutsches Arzneibuch DAB 6. Ausgabe (1926), Československý lékopis 1. vydání (1947), Hagers Handbuch der Pharmazeutischen Praxis (Frerichs et al. 1938), Pharmacopoeia Helvetica V (1953), Österreichisches Arzneibuch 9. Ausgabe (1960), Martindale, The Extra Pharmacopoeia (Wade 1977), Deutsches Arzneibuch DAB 9. Ausgabe (1986), The Complete German Commission E Monographs (Blumenthal et al. 1998), WHO monographs on selected medicinal plants 2002, ESCOP Monographs 2003 and European Pharmacopoeia 6.5 (2009). Bearberry leaf is traditionally used for the treatment of urinary tract disorders.
2.2. Information on traditional/current indications and specified substances/preparations
The following traditional uses have been recorded for bearberry leaf:
The Complete German Commission E Monographs (Blumenthal et al. 1998)
Uses: inflammatory disorders of the efferent urinary tract
WHO Monographs on Selected Medicinal Plants (Volume 2, 2002)
Uses: described in pharmacopoeias and in traditional systems of medicine: as a mild urinary antiseptic for moderate inflammatory conditions of the urinary tract and bladder, such as cystitis, urethritis and dysuria
Uses: described in folk medicine: as a diuretic, to stimulate uterine contractions, and to treat diabetes, poor eyesight, renal or urinary calculi, rheumatism and venereal disease, topically for skin depigmentation
ESCOP Monographs (2003)
Therapeutic indications: uncomplicated infections of the lower urinary tract such as cystitis, when antibiotic treatment is not considered essential
British Herbal Compendium (Bradley 1992)
Bearberry leaf is used as a urinary antiseptic and astringent in mild infections of the urinary tract.
Herbal Medicines. A guide for healthcare professionals (Barnes et al. 2002) Martindale Extra Pharmacopoeia (Wade 1977)
Barberry is a diuretic and astringent and has been stated to exert an antiseptic effect on the urinary tract. It has been employed in urethritis and cystitis.
British Herbal Pharmacopoeia (1996)
Indications: mild infections of the urinary tract
PDR for Herbal Medicines (Gruenwald et al. 2004)
Indications: infections of the urinary tract – for inflammatory disorders of the efferent urinary tract
Standard Zulassungen (1996)
Used as an adjuvant in therapy of bladder and renal pelvis catarrhs.
Martindale, The Extra Pharmacopoeia (2004)
Bearberry has been reported to be a diuretic, bacteriostatic, and astringent and has been used in the treatment of urinary tract disorders.
Schindler et al. (2002)
Bearberry is traditionally used in the treatment of the urinary tract infections (i.e., acute cystitis) with bacteriuria below 105
2.3. Specified strength/posology/route of administration/duration of use for relevant preparations and indications
The following posologies have been recorded for bearberry leaf:
The Complete German Commission E Monographs (Blumenthal et al. 1998)
Herbal Medicines. A guide for healthcare professionals (Barnes et al. 2002)
Martindale Extra Pharmacopoeia (Wade 1977)
Dosagefresh infusion (1:20) 15 – 30 ml; concentrated infusion (1:2.5) 2 – 4 ml; liquid extract (1:1) 2 ml.
PDR for Herbal Medicines (Gruenwald et al. 2004)
Proposed posology for the specified preparations based on the literature data and information received from the Member States:
There is different information on tea preparation in different literature sources. Herbal tea could be prepared by decoction from the powdered herbal substance (DAB 9, Blumenthal et al. 1998; Standard Zulassungen 1996; Weiss, 1985) or as an infusion from cut or powdered herbal substance (Blumenthal et al. 1998; Gruenwald et al. 2004) or by maceration for several hours (Standard Zulassungen 1996; Gruenwald et al. 2004). Results of the research done by Frohne (1970) are summarised in the following table:
The content of tannins has not been taken into consideration by Frohne (1970).
During decoction high amount of tannins is extracted while cold maceration prevents tannins elution (Frohne 2004; Hänsel et al. 1993). Taking in consideration that, in most literature sources, there is a
recommendation to use the comminuted herbal substance in a form of cold macerate or infusion, the following instruction is recommended:
To make a herbal infusion, pour 150 ml of boiling water over 1.5 – 4 g of comminuted herbal substance and steep for 10 to 15 minutes.
To make a macerate, pour 150 ml of cold water over 1.5 – 4 g of the comminuted herbal substance and steep for minimum 30 minutes stirring frequently. The macerate should be used immediately after preparation.
3.1. Overview of available pharmacological data regarding the herbal substance(s), herbal preparation(s) and relevant constituents thereof
3.1.1. Primary pharmacodynamic effects
Bearberry leaf extract
Oral administration of 800 mg of arbutin or an infusion of the leaves containing an equivalent amount of arbutin to healthy volunteers had strong antibacterial activity against Staphylococcus aureus SG 511 and Escherichia coli, as measured in urine samples after adjustment of the urine pH to 8.0. Urine of pH 6 was ineffective (Frohne 1970).
A bearberry leaf extract (liquid extract 1:5, ethanol 70%) exhibited antimicrobial activity towards a variety of organisms including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Mycobacterium smegmatis, Shigella sonnei and Shigella flexeneri (Moskalenko 1986).
A decoction of bearberry leaf (10 g/100 ml water) increased remarkably the hydrophobicity of both E. coli and Acinetobacter baumanii strains in vitro. There was no growth registered after the exposure of 20 different E. coli strains to the undiluted decoction of bearberry and in case of
bacteria mainly caused by increased hydrophobicity of their cell surface (Türi et al. 1997). A bearberry leaf aqueous extract (decoction 1:10/30 min/100°C/pH 4.7) exhibited a similar effect on Helicobacter pylori (Annuk et al. 1999).
The antimicrobial activity of an ethanolic extract (ethanol 80%) of the aerial parts of A.
The antimicrobial activity of extracts depends on the extraction solvent used. There is some evidence that extracts prepared with ethanol of high concentration have less activity. An aqueous extract of bearberry leaves inhibited the growth of Streptococcus mutans OMZ176 in vitro (Namba et al. 1981). A 30% ethanol extract of Uvae ursi folium inhibited the growth in vitro of Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Serratia marcescens and Staphylococcus aureus (WHO 2002). However, 95% ethanol or chloroform extracts had no antibacterial activity (Ríos et al. 1987; Gottshall et al. 1949; WHO 2002).
The bearberry leaf extract (95% ethanolic extract – 15:100 material to solvent ratio) alone displayed no antimicrobial activity against any of the 25 bacteria tested (Dykes et al. 2003).
An aqueous extract of bearberry leaves (no other information on the type of extract and DER) was administered intraperitoneally (i.p.) to 10 male rats as a single dose of 50 mg/kg body weight; a control group of 10 rats received hypotonic saline solution and another group of 10 rats received the diuretic compound hydrochlorothiazide at 10 mg/kg body weight. The urine volume from rats treated with the extract was significantly higher (p<0.001 from the 4th to 8th hour after administration; p<0.05 over a
Contrary results to that in the above mentioned study were obtained in another experimental study in which diuretic effect of several flavonoid drugs including Uvae ursi folium was investigated. The following preparations were administered to dogs: the flavonoid fraction isolated from the crude drug, a dry methanolic extract, a dry aqueous extract, a decoction and an aqueous suspension of the pulverised drug. The starting herbal substance contained 1.5% of total flavonoids. Preparations of Uvae ursi folium inhibited diuresis (Borkowski 1960 – abstract).
Additionally, no diuretic effect of
In a study in humans, urine samples collected after administration of 0.1 or 1 g of arbutin with or without additional use of 0.250 g of Diuramid® (acetazolamide) to achieve alkaline urine were tested on the antibacterial activity against 74 strains of bacteria including Escherichia coli, Proteus mirabilis, Proteus vulgaris, Proteus rettegeri Klebsiella, Enterobacter, Citrobacter freundii, Pseudomonas aeruginosa and Staphylococcus aureus. The results were compared with the results of other
20 antimicrobial compounds. Only arbutin (present in urine samples collected after administration of 1 g arbutin), gentamycin and nalidixic acid were active against all strains tested. An antimicrobial effect was apparent even after administration of 0.1 g of arbutin. The effect of arbutin was higher in alkaline urine in comparison to urine with pH 6. In this study, arbutin or free hydroquinone were not detected in urine samples (Kedzia et al. 1975).
The antimicrobial activity of arbutin towards bacteria implicated in urinary tract infections was found to be directly dependent on the
Arbutin and its metabolite hydroquinone showed inhibition of the growth of Ureaplasma urealyticum and Mycoplasma hominis in vitro (WHO 2002; Robertson and Howard 1987).
Other sources associate the antimicrobial effect of
Despite various pharmacological investigations, it is still debated whether the antibacterial effect in the urine is caused by hydroquinone esters, especially the sulphate ester, or by free hydroquinone liberated from them in alkaline urine (Kedzia et al. 1975).
It has even been suggested that arbutin could be hydrolysed directly to hydroquinone in the urinary tract by
Tannic acid seems to be a component of bearberry aqueous extract with the highest activity to decrease cell surface hydrophobicity as well as antibacterial activity against H. pylori (Annuk et al. 1999).
3.1.2. Secondary pharmacodynamic effects
Bearberry leaf extract
The effect of 50% methanolic extract from bearberry leaf on the
An aqueous extract of the leaves (prepared from 1 part of the herbal substance and 10 parts of water) had antiviral activity in vitro against Herpes simplex virus type 2, influenza virus A2 (Mannheim 57) and vaccinia virus at a concentration of 10% (May and Willuhn 1978; WHO 2002).
Addition of an infusion of the leaves to the
The effect of a 50% methanolic extract from bearberry leaf on melanin synthesis was investigated in vitro. Bearberry leaf extract as well as arbutin isolated from bearberry leaves had an inhibitory effect on the tyrosinase activity. Furthermore bearberry leaf extract inhibited the production of melanin from dopa by tyrosinase and from dopachrome by autoxidation (Matsuda et al. 1992a – abstract).
Water extracts (infusions) from a group of medicinal plants were studied in terms of their activity enhancing the uterine tonus in a series of experiments with a preparation of an isolated rabbit and
guinea pig uterine horn. Infusion of bearberry leaves did not show any uterotonic effect (Shipochliev 1981).
In mice orally or i.p. treated with arbutin
Male and female cats (none anaesthetised) were administered oral (p.o.) and i.p. doses of 50 and 100 mg/kg [0.18 or 0.367 mmol/kg] body weight arbutin in water and observed at
Arbutin (in concentrations 90 g/ml and 40 g/ml) did not inhibit the growth of rat hepatoma cells (Assaf et al. 1987; Barnes et al. 2002; Herbal Medicines 2008).
3.1.3. Pharmacodynamic drug interactions
Bearberry leaf extract
In mice, A.
Water extracts from the leaf of A.
Arbutin plus indomethacin showed a stronger inhibitory effect than indomethacin alone in carrageenan- induced oedema and
Arbutin exhibited potent inhibitory effects on rat platelet aggregation induced by adenosine diphosphate (IC50=0.12 mM) and collagen (IC50=0.039 mM) and displayed the same inhibitory activities as the positive control, tetramethylene glutaric acid, on rat lens aldose reductase (Lim et al. 2003 [Korean with English summary]; NTP 2006).
3.2. Overview of available pharmacokinetic data regarding the herbal substance(s), herbal preparation(s) and relevant constituents thereof
Arbutin, the major constituent of Uvae ursi folium extracts, is a phenolic glycoside, which splits into hydroquinone (HQ) and glucose (Jahodář et al. 1985). HQ is the recognised active substance at the site of drug action, which is the lower urine tract. The total amount of HQ (free HQ and HQ- conjugates) in urine is crucial for the therapeutic activity of the herbal preparation. Therefore, human pharmacokinetic studies have been focused on the availability of total HQ in urine and the use of HQ and arbutin as pharmacokinetic markers is plausible (Paper et al. 1993; Schindler et al. 2002; Quintus et al. 2005).
Bearberry leaf extract
The ability of bearberry leaf to act against urinary infections is believed to be the result of action of free hydroquinone cleaved from the arbutin molecule in the urinary tract. It is not known in which tissue this cleavage occurs in vivo and what amount of hydroquinone is present in the organisms after treatment with arbutin. The cleavage is mediated via
After ingestion of the leaves, arbutin is absorbed from the GI tract, and is hydrolysed by intestinal flora to form the aglycone, hydroquinone (Paper et al. 1993). Hydroquinone is metabolised to glucuronide and sulfate esters that are excreted in the urine (Kedzia et al. 1975; Frohne 1970). These active hydroquinone derivatives exert an antiseptic and astringent effect on the urinary mucous membranes when the urine is alkaline (pH 8). Their antibacterial action reaches a maximum approximately 3 – 4 hours after ingestion (Blumenthal et al. 1998; Paper et al. 1993).
The bioavailability of
Five bearberry leaf products were tested to determine their influence on CYP 3A4, 3A5, 3A7, 2C19 and
Inhibitory effect of aqueous and methanolic Uvae ursi extracts on CYP3A isoenzymes was proved in in vitro tests (Chauhan et al. 2007). Possible interaction with finasteride should be taken into consideration as in vitro evidence suggests that agents which inhibit CYP3A activity are likely to inhibit the metabolism of finasteride (Wilde and Goa 1999).
As arbutin is reported to hydrolyse easily in diluted acids to yield
Female Wistar rats were given an aqueous solution of chromatographically pure arbutin, isolated from A.
The highest glucosidase extracellular enzymatic activity was found in the genera Streptococcus faecalis (100%), Klebsiella (95%), and Enterobacter (72%), the lowest in Escherichia coli (11.6%). A direct dependence of the antimicrobial effect of arbutin on the level of the enzymatic activity of microorganisms was found. The presumption of the autocidal action of some bacteria on arbutin was confirmed. The minimal bactericidal concentration of arbutin ranges from 0.4 to 0.8%, in dependence on the species of the microorganism (Jahodář et al. 1985).
Oral administration of arbutin (500 mg/kg [1.84 mmol/kg]) to female rats which were overloaded with fluid resulted in a
Investigations were performed in animals to elucidate the absorption, metabolism and elimination of arbutin. Isolated segments of the intestine from the distal part of the duodenum and the caecum of hamster and chicken were used in an in vitro model to study in detail the absorption process of arbutin. Experimental data in vitro indicate that arbutin is absorbed via the Na+/glucose carrier in the small intestine. The transport of arbutin in the small intestine was a freely reversible process, also used by glucose and its analogues (Alvarado 1965; Alvarado and Monreal 1967).
Arbutin uptake has been also investigated in human small intestine obtained from biopsies of
18 patients with minor abdominal complaints without obvious gastrointestinal disease. In 3 patients,
Oral administration of [14C]hydroquinone either in the diet or by gavage to
5 – 10 s. Later blood sampling
Following oral administration to rats, by far the major proportions of metabolites are conjugates of glucuronic (up to 67%) and sulfuric (up to 33%) acids. The remaining urinary metabolites consist of 0 – 5 % mercapturates, 0 – 3% unconjugated hydroquinone and <1% unconjugated 1,4 – benzoquinone.
The oxidation of hydroquinone to the very reactive
3.3. Overview of available toxicological data regarding the herbal substance(s)/herbal preparation(s) and constituents thereof
Bearberry leaf extract
No data on single or repeated dose toxicity have been reported for bearberry leaf extract. There are no data on reproduction toxicity or drug interaction available.
Uvae ursi folium (dry aqueous extract) has not been mutagenic in the Salmonella/microsome assay with S. typhimurium strains TA98 or TA100 as well as in the Bacillus subtilis
The cytogenetic effect of ethanolic extracts of Uvae ursi folium on irradiated human blood lymphocytes was assessed. Micronucleus formation in unirradiated and irradiated samples of cultured blood lymphocytes using the cytochalasin block micronucleus test was examined. The treatment of cells with bearberry leaf extract did not affect the level of micronuclei in any of the concentration studied (0.025, 0.05, 0.1, or 0.2 mg/ml) (Joksic et al. 2003; NTP 2006).
There was no evidence of carcinogenic activity of an aqueous extract of the Uvae ursi leaves in male B6C3F1 mice (treated by gavage with 50 – 100 mg extract/kg body weight) (NTP 1989, 2006; WHO 2002).
Repeated dose toxicity of arbutin has been investigated in mice. At a dose of 8 g/kg [29.38 mmol/kg] administered i.p. for 2 weeks, no toxic effects were observed (Li et al. 1982 [Chinese]; NTP 2006).
Arbutin (up to
The ames test and the micronucleus test have been performed with urine containing arbutin. Results have shown no indication of genotoxicity related to arbutin (Siegers et al. 1997).
There are study results providing information that arbutin (2.5, 12.5, or 50 μg/ml [9.2, 45.9, 180 μM]) incubation for 4 days weakly inhibited the growth of human colon carcinoma
Reproduction and developmental toxicity
Arbutin was administered subcutaneously at 25, 100 or 400 mg/kg of body weight daily to male
Oral application of arbutin (10 or 50 mg/kg [0.037 or 0.18 mmol/kg]) quickly reduced the swelling caused by picryl chloride and sheep red cell delayed type hypersensitivity in mice within 24 hours (Matsuda et al. 1990, 1991 [Japanese, abstract]). Arbutin (1 mg/ml [4 mM]) inhibited the binding of mouse monoclonal
In macrophage cells from male Swiss mice, arbutin (2 mg/ml [7 mM]) failed to induce the release of hydrogen peroxide (Moreira et al. 2001; NTP 2006).
Growth of human melanoma cells and normal human melanocytes was not inhibited by exposure to 100 μg/ml [0.367 mM] arbutin for 5 days. At 300 μg/ml [1.10 mM] arbutin treatment for 5 days, cell toxicity and detachment of cells from the dishes were observed within 48 hours (NTP 2006).
Arbutin (5 – 50 μM [1 – 14 μg/ml]) inhibited the growth of the roots of Allium sativum L. and produced
The toxicology of free hydroquinone (HQ) has been reconsidered in several published reviews and it was concluded that there is no evidence to suggest that the toxicology of free HQ is of human relevance (Deisinger et al. 1996; DeCaprio 1999 – abstract; McGregor 2007).
In previous sections, it has been addressed that the active component of bearberry leaf extract, arbutin, is converted to free HQ to exert its antibacterial effect. Based on the pharmacokinetic profile of arbutin, it has been shown that free HQ has an irrelevant accumulation risk since arbutin is very fast conjugated and transformed in innocuous metabolites.
Only in a very low percentage (0.6% of the given dose) free HQ is eliminated via the urine and (<1%) in feces. Most of the arbutin is therefore transformed in to HQ conjugates (70%) (Siegers et al. 1997; 2003). Free HQ is not accumulated in the animal or human organism and its potential accumulation is not justified by any pharmacodynamic/pharmacokinetic reason (English and Deisinger 2005).
Acute toxicity data on hydroquinone were published. The oral LD50 of hydroquinone in 2% aqueous solution has been determined as 320 mg/kg in rats, 400 mg/kg in mice, 550 mg/kg in guinea pigs, 300 mg/kg in pigeons, 70 mg/kg in cats and 200 mg/kg in dogs (Woodard et al. 1949).
Acute exposure of rats to high doses of hydroquinone (over 1300 mg/kg body weight) caused severe effects on the central nervous system, including hyperexcitability, tremor, convulsions, coma and death (IPCS 1994).
The presence of food may increase oral LD50 values of 310 to 1050 mg/kg in rats. Thus, food showed to decrease the rate and extent of free HQ absorption. LD50 values for free HQ by parenteral administration have been reported as 115 – 160 mg/kg in the rat and 190 mg/kg in the mouse (DeCaprio 1999 – abstract). In the course of toxicological animal experiments, free HQ demonstrated a very low toxicity since LD50 values were very high. In addition, the presence of food importantly improves its safety.
Hydroquinone was negative for mutagenicity in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 in the presence and absence of metabolic activation (S9). In Chinese hamster ovary cells, it induced sister chromatid exchanges (with and without S9) and chromosomal aberrations (with S9).
Hydroquinone also induced trifluorothymidine resistance in mouse L5178Y/TK lymphoma cells and was mutagenic in the micronucleus test. Inconclusive results, however, were obtained in Drosophila (NTP 1989; NTP 2006). However, hydroquinone was found to be mildly myeloclastogenic in the micronucleus test in SPF mice after oral administration of a toxic dose (200 mg/kg)
The DNA reactivity of hydroquinone has been documented in animals and this enhanced activity is presumably due to the oxidised forms of hydroquinone,
Hydroquinone is generally not active in bacterial tests for mutation, but it has been reported to cause
Hydroquinone induced micronuclei and chromosomal aberrations in several studies in
Hydroquinone is mutagenic in vitro and in vivo, but the administration route used to demonstrate the in vivo activity is inappropriate and exposure by more appropriate routes, methods and doses allow protective mechanisms to contain the potentially damaging effect of the oxidative properties of hydroquinone (McGregor 2007).
Relatively more information on carcinogenicity is available for hydroquinone and its derivatives. The health effects of hydroquinone have been extensively reviewed in IPCS Environmental Health Criteria No. 157 and summarised in IPCS Health and Safety Guide No. 101 (IPCS 1994; IPCS 1996; NTP 2006).
Although extracts of the leaves do not appear to be carcinogenic, there is some evidence that hydroquinone is carcinogenic. In a
In a U.S. National Toxicology Program study, groups of 55 male and 55 female Fischer 344/N rats, 7 to 9 weeks of age, were administered 0, 25, or 50 mg/kg body weight hydroquinone (purity >99%) by gavage on 5 days per week for 103 weeks. Survival was reduced in exposed rats. Also, the mean body weight of exposed males was reduced and the relative kidney weights for high dose males were greater than those for vehicle controls (NTP 1989).
Nephropathy was observed in nearly all male and most female rats of all dosed groups and vehicle controls. The nephropathy was characterised by degeneration and regeneration of tubule epithelium, atrophy and dilatation of some tubules, hyaline casts in the tubule lamina, glomerulosclerosis, interstitial fibrosis, and chronic inflammation. In males, the nephropathy was more severe in the high- dose (50 mg/kg body weight per day) group, while in females no dose dependence was observed. Nephropathy had also been observed in males in earlier
In exposed males, renal
A reanalysis of the histology of the NTP study, in addition to demonstrating a low incidence of foci of atypical tubule hyperplasia and small adenomas at both doses, also found substantial exacerbation of chronic progressive nephropathy (CPN) to end stage grades of severity at the high dose (Hard et al.
1997). Briefly, CPN begins at about 2 months of age, when some rats develop basophilic renal tubules with a thickened basement membrane. Progression involves an increase in number of tubules affected, tubule degeneration and atrophy, and an ongoing
The histopathological reanalysis of the hydroquinone study (Hard et al. 1997) found that of the
8 tumours identified by NTP in the high dose, 4 were definite adenomas (one being a cystadenoma), 3 were very early adenomas (incipient adenomas), and 1 was a focus of atypical hyperplasia. In the low dose, 3 of the 4 tumours diagnosed by NTP were similar to the high dose tumours diagnosed by Hard et al. (1997), 2 being definite adenomas and 1 a very early adenoma; the fourth was considered
to be a metastasis from a mesothelioma that was present in the peritoneal cavity and certain lymph nodes in this rat, which died at 56 weeks. Besides the 1 focus of atypical hyperplasia already mentioned, Hard et al. (1997) found 13 other foci of atypical hyperplasia in 11 of the 51 rats examined, whereas only 2 were mentioned in the NTP report. Only one of these was confirmed in the
Reproduction and developmental toxicity
There are no germ cell studies of hydroquinone mutagenicity in which routes other than i.p. have been used. Unlike the adult human anatomy, the testes of adult rats are likely to receive direct exposure to a chemical that is delivered by the i.p. route because the inguinal canal remains open. The i.p. route would seem to largely destroy any rationale for testing in vivo because exposure of many in vivo target cells in animals dosed by this method differs little from that achieved in vitro. Although it is not clear that dominant lethal assays are truly
Hydroquinone has been reported to show a
3.4. Overall conclusions on
Available pharmacodynamic data regarding antibacterial activity of bearberry leaf extract together with experiments performed with arbutin or hydroquinone provide solid ground for bearberry leaf extract to be assessed as useful antibacterial agent to treat early symptoms of mild infections of the lower urinary tract.
There are no data on safety pharmacology of bearberry leaf extract or its component arbutin and metabolite hydroquinone available at present. It is not possible to conclude any information on drug effect on central nervous system, cardiovascular system or respiratory system. Taking into account the difference in metabolism of arbutin in humans and animals, and metabolism ambiguity of arbutin to hydroquinone together with the fact that bearberry extract seems to be more active in patients compared to the healthy subjects further
Bearberry leaf extract
There is almost no information available on the toxicity of crude extract of bearberry leaves. Bearberry crude extract was evaluated in Ames test using only 2 instead of 5 recommended strains. Results of this study were negative; however, clear conclusion about genotoxicity of the extract could not be made. Bearberry leaf extract was also negative in the in vitro micronucleus test; however, this test was not performed according to ICH S2B standard. Studies in mice revealed there is no carcinogenic potential of bearberry leaf extract.
Single dose toxicity study has not been performed with arbutin but repeat administration of doses much higher compared to that in clinical practice revealed no toxic effects in mice.
Arbutin has been evaluated in vitro in Ames assay and micronucleus test showing no indication of genotoxic potential. The chinese hamster V79 mutation test performed with arbutin gave negative results. Whilst after preincubation of arbutin with
Carcinogenicity studies have not been performed with arbutin.
Reproduction and developmental studies performed in rats dosed with arbutin showed that there is no risk on male and female fertility and no deaths were observed in offsprings. The results of the study are considered irrelevant to clinical practice since low doses of arbutin were used.
Acute toxicity of hydroquinone has been evaluated and lethal doses were established in several animal species. High exposure of rats to hydroquinone led to severe toxic effect on the central nervous system.
Genotoxicity and mutagenicity of hydroquinone has been extensively studied but clear conclusion could not be made. While the standard Ames assay was negative, sister chromatide exchange, chromosomal aberrations, mouse lymphoma assay and micronucleus test were positive after treatment with hydroquinone. Unambiguous conclusion based on these results could not be made. Firstly, doses of the hydroquinone used in the studies are much higher than is expected as clinical dose after administration of bearberry leaf extract. Secondly, in the in vivo studies hydroquinone was mainly administered intraperitoneally. In case of oral administration, results were often negative and toxic effects described as mild. Furthermore hydroquinone is a naturally occurring substance and the human body is commonly exposed to this substance. Hydroquinone is present in coffee, tea or pears and low parts-
Free hydroquinone showed no mutagenetic risk in several in vitro and in vivo assays. The potential mutagenicity of free hydroquinone occurred only at concentrations that excess more than 20 times the maximal theoretical concentration reached in an animal or human organism (2.4 mg/kg; when all arbutin was transformed in free hydroquinone). As a response to this possibility, the organism has a potent conjugation metabolism to neutralise the hydroquinone just after its formation.
The safety margin could be considered sufficient regarding toxicity and adverse effects.
Furthermore, it should be considered that available data did not report any serious adverse and toxicity effects in animals after administration of arbutin or hydroquinone doses relevant for human use and assessment of human safety.
No adverse toxic reactions have been reported in scientific literature and several types of bearberry leaf extract have been in medicinal use for many years. Therefore
4. Clinical Data
4.1. Clinical Pharmacology
4.1.1. Overview of pharmacodynamic data regarding the herbal substance(s)/preparation(s) including data on relevant constituents
The antiseptic and diuretic properties claimed for bearberry leaf extract can be attributed to the hydroquinone derivatives, especially arbutin. Arbutin is absorbed from the GI tract virtually unchanged and during renal excretion is hydrolysed to yield the active principle, hydroquinone, which exerts antiseptic and astringent action on the urinary mucous membranes (Frohne 1970).
The crude extract of bearberry leaf is reported to be more effective as an astringent and antiseptic than isolated arbutin. This may be due to the other hydroquinone derivatives, in addition to arbutin, that are present in the crude extract and which will also yield hydroquinone. It has been stated that the presence of gallic acid in the crude extract may prevent
Pharmacodynamic drug interactions
Bearberry leaf extract
There were no drug interactions documented for bearberry leaf extract (Herbal Medicines 2008). However, it was observed that the sodium sparing effect of bearberry leaf extract may offset the diuretic effect of thiazide and loop diuretics (Gruenwald et al. 2004). As information on sodium sparing effect is not supported by any published case report, this interaction is not included in the Community herbal monograph.
In a study without controls, urine samples from healthy volunteers were collected 3 hours after oral administration of 0.1 or 1 g arbutin. The urine samples (adjusted to pH 8) and 20 antibacterial compounds (at their usual urine concentration) were tested in vitro using 74 strains of bacteria, including Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa and Staphylococcus aureus. Only arbutin (present in urine samples collected after administration of 1 g arbutin), gentamicin and nalidixic acid were active against all the strains tested. Antibacterial effect was observed also at
Oral administration of arbutin (800 mg) or an infusion of the leaves containing an equivalent amount of arbutin to healthy volunteers had strong antibacterial activity, as measured in urine samples after adjustment of the urine pH to 8.0 (Frohne 1970). With respect to the slight toxicity of arbutin its metabolic product could be used as an effective antibacterial substance in the alkaline environment against bacterial infection of the urinary tract (Frohne 1977).
The antibacterial effect of bearberry leaf extract according to the hypothesis formulated already in 1883 is ascribed to hydroquinone which is liberated from arbutin via glycoside cleavage. Therefore, arbutin is the prodrug of the relatively toxic active principle hydroquinone. In the case of arbutin, hydrolysed by
In urine hydroquinone exists in form of glucuronide and after alkalinisation of the urine, it splits to the free form having antibacterial activity (ESCOP 2003).
It is still unknown which of the hydroquinone compounds are responsible for the antibacterial effect. Investigation data revealed that hydroquinone glucuronide could not be responsible for antibacterial activity since its maximum in urine was detected 2 hours after administration of arbutin and maximum antibacterial activity of urine was observed at 3 to 4 hours
Alkalisation of urine
Urine samples from healthy volunteers received
Urine with high content of metabolic products of arbutin leaving on the air clearly showed low potency for bacterial infections compared to the control urine sample. Bacterial culture incubation (E. coli and Staphylococcus aureus) showed a clear inhibitory effect of urine containing metabolic products of arbutin. This urine sample has to be alkaline. Alkalisation alone or addition of arbutin alone did not show any bacteriostatic effect in the sample of urine (Frohne 1977).
Whether the alkalising of the urine – which, through the administration of sodium hydrogen carbonate, can be attained only
A problem is the way of making the urine environment more alkaline. The common daily dose of natrium hydrogencarbonate or dinatrium phosphate is able to alkalinise urine only for a short period of time. Kedzia et al. (1975) suggested using Diuramid® which is able to make urine alkaline for longer period; however, due to its toxicity, it could be administered only for 3 or 4 days. Frohne stated that further investigation of how to alkalinise urine in a much more effective manner is necessary (Frohne 1977).
Since concomitant acidification of the urine (by other remedies) may result in a reduction of its antibacterial efficacy, several references included statements on patients being advised to avoid eating highly acidic foods, such as acidic fruits and their juices during treatment with Uvae ursi folium (WHO 2002; Barnes et al. 2002; ESCOP 2003; Gruenwald et al. 2004).
However, a study from 2003 demonstrated that bacteria causing urinary tract infections participate in the deconjugation of arbutin and liberate the toxic free hydroquinone. The free hydroquinone then can damage the cell by destabilisation of its membranes. Alkalisation of the urine by intake of sodium
bicarbonate is not necessary considering the effective bacterial deconjugation by E. coli, the principal agent in urinary infections (Siegers et al. 2003).
4.1.2. Overview of pharmacokinetic data regarding the herbal substance(s)/preparation(s) including data on relevant constituents
The main constituent of Uvae ursi folium extracts is arbutin, a phenolic glycoside splits in hydroquinone and glucose (Jahodář et al. 1985). Free hydroquinone is the recognised active substance at the site of drug action that is the lower urine tract. The total amount of hydroquinone (free hydroquinone and conjugated hydroquinone) in urine is considered crucial for the therapeutic activity of the herbal extract. Therefore, pharmacokinetic studies have been mainly focused on the availability of total hydroquinone in the urine. The use of hydroquinone and arbutin as pharmacokinetic markers is reasonable and justified (Paper et al. 1993; Schindler et al. 2002; Quintus et al. 2005).
Bearberry leaf extract
Four hours after ingestion of a single dose of a preparation containing bearberry leaf extract (945 mg corresponding to 210 mg arbutin), 224.5 μmol/L hydroquinone glucuronide and 182 μmol/L hydroquinone sulfate were recovered in the urine of one volunteer, which represented approximately half of the administered arbutin dose (Glöckl et al. 2001).
In an open, randomised,
Twelve human volunteers (6 males and 6 females) received 3 x 2 dragees containing 238.7 – 297.5 mg of bearberry leaf dry extract (DER 3.5 – 5.5:1, extraction solvent ethanol 60% V/V corresponding to 70 mg of arbutin) in one tablet. The urine was sampled for 36 hours and fractionated in periods of 6 hours. Free and conjugated hydroquinone was measured in the samples. Only 0.6% of the administrated arbutin dose (420 mg) was excreted as free hydroquinone and in 6 out of 12 volunteers no free hydroquinone was detected in urine (detection limit 0.3 g/ml); 70% of the arbutin dose was found as hydroquinone conjugated to glucuronic and sulfuric acid. Urine samples collected in this study were assayed with or without added glusulase (mixture of
Arbutin was found to be extensively absorbed from the GI tract and bioavailable as hydroquinone. Volunteers (2 males and 2 females, 36 – 45 years old) receiving a diet containing high levels of arbutin and hydroquinone (coffee or tea, wheat cereal, whole wheat bread, wheat germ and Bosc pears) had significant increases in mean total hydroquinone (i.e., hydroquinone and its conjugated metabolites) plasma levels. After 2 hours, it was 5 times the background concentration (at 0.15 μg/g [0.55 nmol/g]). Urinary total hydroquinone excretion rates were also significantly increased; after 2 to 3 hours, levels were 12 times background levels. A
cantaloupe, black cherry yogurt and soft drink) resulted in a slight decrease in the mean levels of hydroquinone in human plasma and urine (Deisinger et al. 1996).
Most studies of hydroquinone kinetics and metabolism following oral administration have used arbutin or another form of bearberry leaf extract. For information on hydroquinone kinetics, see sections above.
4.2. Clinical Efficacy
4.2.1. Dose response studies
Dose response has been investigated in healthy volunteers. Antibacterial effect has been observed after administration of 0.1 or 1 g of arbutin. Lower dose provided lower antibacterial effect but, independently of the dose, the pH value of urine was the most important factor determining the antibacterial activity (Kedzia et al. 1975).
According to Frohne (1970), the effective concentration of arbutin should be higher than 0.3%.
4.2.2. Clinical studies (case studies and clinical trials)
Bearberry leaf extract
Clinical research assessing the effects of bearberry leaf extract as a single substance/preparation is not available at the time of the preparation of this report.
Results of three controlled clinical trials with bearberry leaf extract in combination with other herbal extracts are available.
In the first clinical trial, the effect of a combination product (oral solution containing liquid extracts from Uvae ursi folium, Betulae folium, Equiseti herba, Virgaureae herba, Juniperi
The effect in the treatment of urinary tract infection caused by a
The third clinical study assessed the prophylactic effect of another combination product (containing hydroalcoholic extract of bearberry leaves with a standardised content of arbutin and methyl arbutin, and of dandelion root and leaf) on recurrent cystitis. The product had a prophylactic effect on recurrent cystitis in a
conclusion that bearberry leaf extract is not the treatment of choice for acute cystitis but it could have a possible prophylactic role in the treatment of recurrent urinary tract infections. However, this conclusion cannot be made with certainty (Larsson et al. 1993).
Table 1: Overview of clinical studies with Uvae ursi folium preparations (combination products) in urological indications:
4.2.3. Clinical studies in special populations (e.g. elderly and children)
There are no clinical studies in special population available for bearberry leaf extract or for arbutin.
4.3. Overall conclusions on clinical pharmacology and efficacy
Available controlled clinical trials evaluated the effect of bearberry leaf extract in combination with other herbal substances. There are no clinical studies evaluating the efficacy of bearberry leaf extract alone that would be suitable to support the
Based on results of in vitro tests on antimicrobial activity of bearberry leaf preparations containing arbutin as a main active component and long standing use of bearberry leaf extract for treatment of uncomplicated infections of the lower urinary tract, the traditional use of bearberry leaf extract in the
Clinical significance of bearberry leaf extract administration with respect to the hydroquinone exposure should be considered taking into account that even without administration of bearberry leaf extract hydroquinone can be naturally found in the human body. Hydroquinone is naturally contained in coffee, tea or wheat cereals.
5. Clinical Safety/Pharmacovigilance
5.1. Overview of toxicological/safety data from clinical trials in humans
There is a lack of clinical safety and toxicity data for bearberry leaf extract and further investigation of these aspects should be performed.
Bearberry leaf extract in combination with dandelion root and leaf extract, used in a treatment study of 57 women with recurrent cystitis, produced no side effects. After one year of treatment, 5/27 women in the placebo group had a recurrence compared to 0/30 women in the treatment group. Neither group reported side effects (Larsson et al. 1993).
5.2. Patient exposure
There are no special data on patient exposure to bearberry leaf extract or arbutin available.
Several cohort studies were performed with workers getting in daily contact with hydroquinone. Workers were engaged in colour printing and processing, in a plant where hydroquinone was manufactured, as lithographers or in motion picture film processing.
Results of the evaluation led to the conclusion that adverse effect could not be directly attributed to the hydroquinone exposure; the studies were mostly of poor quality. Some other substantial parameters were not followed and evaluated such as cigarette smoking habits. Finally, it should be considered that many other chemicals were used in the examined working environment (McGregor 2007).
5.3. Adverse events and serious adverse events and deaths
The internal use of Uvae ursi folium may cause nausea and vomiting due to stomach irritation from the high tannin content (WHO 2002; Blumenthal et al. 1998; Gruenwald et al. 2004; British Herbal Pharmacopoeia 1996; ESCOP 2003; Bradley 1992). Stomach ache has also been reported as adverse effect (Gruenwald et al. 2004; Hänsel et al. 1993).
In view of the high tannin content and toxicity of hydroquinone, prolonged use of bearberry leaf extract may cause chronic liver impairment (Barnes et al. 2002; Herbal Medicines 2008; Gruenwald et al. 2004).
In persons with sensitive stomachs, nausea and vomiting are possible side effects after ingestion of dried bearberry leaves (as low as 15 g). Other symptoms that have been reported in association with bearberry leaf extract are irritability, insomnia and increased heart rate (NTP 2006).
Uvae ursi leaf extract use has also been linked to albuminuria, hematuria and urinary cast (Adesunloye 2003; NTP 2006).
Due to the high tannin content of the leaves, the tea infusion tastes bitter and astringent which can lead to nausea and vomiting in patients with sensitive stomachs. Hydroquinone appears to be non- toxic with the administration of bearberry leaf tea; however, hydroquinone must remain in suspicion with regard to having mutagenic and possibly carcinogenic effects (Frohne 2004).
Uvae ursi folium should not be used for prolonged periods. Patients with persistent symptoms of a urinary tract infection should consult a physician. Use of Uvae ursi folium may cause a
5.4. Laboratory findings
Laboratory screening tests were performed within an open, randomised,
5.5. Safety in special populations and situations
The safety of bearberry leaf extract in human is mainly based on the traditional use. There are only several clinically reliable data regarding safety of the extract after administration in human.
Incidence of urinary tract infections in men
UTIs are the second most common form of infection, accounting for nearly 25% of all infections. Incidence of UTIs is significantly higher in women than in men. Incidence of UTIs in men is increasing with age. Asymptomatic bacteriuria is believed to affect up to 50% of geriatric women and 30% of geriatric men. Asymptomatic bacteriuria is prevalent in elderly population but it frequently resolves without treatment and has no
For males aged 17 – 79 years, the mean annual UTI incidence is 2.2 %, for males aged 80 years, the mean annual UTI incidence rises to 5.3 % and risk factors in this age include presence of an indwelling urinary catheter, hospitalization and anatomical abnormalities associated with aging or disease (e.g. benign or malignant prostatic hyperplasia). The incidence of UTIs in men is significantly lower than in women. In women aged 15 – 39 years, the mean annual UTI incidence is 15.2 % and with age falls to 11.4 % for women aged 40 – 59 years and to 9.7 % for women aged 60 – 79 years (Guay 2008). Guay (2008) also reports on a study describing epidemiology of UTIs in a
Much higher incidence of UTIs in females during adolescence and childbearing years (adult women are 30 times more likely than men to develop a UTI) is reported also by Brusch (2011). The frequency of UTI in men approaches that of women only in men older than 60 years; in men aged 65 years or older,
10% have been found to have bacteriuria, as compared with 20% of women in this age group. In the normal host, UTI in men may occur due to infection of other parts of the genitourinary tract, typically the prostate. Older males with prostatic hypertrophy have incomplete bladder empting, predisposing them to UTI on the basis of urinary stasis. However, in males aged 3 months to 50 years, the incidence of UTI is low; therefore, the possibility of anatomic abnormality must be considered. In males older than 50 years, prostatic hypertrophy with partial obstruction is the main contributor to the increase UTI (Brusch, 2011).
Among complications of benign prostatic hyperplasia (BPH) resulting from persistent failure of the bladder to empty or store urine recurrent urinary tract are mentioned (Lee, 2000). In patients with mild symptoms of BPH, whose symptoms do not cause unacceptable distress, no drug therapy with – adrenergic antagonists or with finasteride is yet necessary, and
Neisseria gonorrhoeae and Chlamydia trachomatis are clinically important infectious causes of urethritis (Workowski and Berman 2006).
According to reports on the traditional use no differentiation between the genders was done. While recurrent mild infections of the lower urinary tract are usually uncomplicated in women, a delayed consultation of a medical doctor may imply serious risks for men. Incidence of UTIs in men is significantly lower than in women. Incidence of UTis in young men is very low and risk of anatomical abnormalities, acute inflammations of lower urinary tract such as acute prostatitis or acute epididymitis, as well as sexually transmitted diseases such as gonorrhoea and Chlamydia infections should be taken in consideration by a medical doctor. In men over 50 years, incidence of UTIs is increasing due to prostatic hyperplasia (benign or malignant) and presence of an indwelling catheter. Both, prostatic hyperplasia and indwelling catheter require medical supervision.
The criterion of the Article 16 a) of Directive 2001/83/EC for traditional herbal medicinal products “they have indications exclusively appropriate to traditional herbal medicinal products which, by virtue of their composition and purpose, are intended and designed for use without the supervision of a medical practitioner for diagnostic purposes or for prescription or monitoring of treatment” is not fulfilled for use in men. Therefore, the use in men is excluded from the traditional use and traditional use can be recommended for females only.
A posology for children and adolescents was published in Kinderdosierungen von Phytopharmaka (Dorsch et al. 1998) for bearberry leaf:
Dosage in children:
However, posology data for children is not supported by any clinical data (clinical studies, post marketing reports). The data published by Dorsch et al. (1998) are derived from calculations only.
Furthermore, the use in children and adolescents cannot be recommended for traditional use because infections of the urinary tract, even in their early stage, in children and adolescents should be treated under medical supervision.
An overdosing with bearberry leaf extract can lead to inflammatory irritation of the bladder and urinary tract mucosa accompanied with dysuria and hematuria, or later with blood excreta. Finally, overdosing could lead to liver damage (hepatic impairment) (Gruenwald et al. 2004; Hänsel et al. 1993).
Extremely high doses of bearberry leaf extract (i.e., ten times the recommended amount) can cause ringing in the ears, shortness of breath, convulsions, collapse, delirium, and vomiting. Liver damage is a risk with
Large doses of bearberry leaf extract are reported to be oxytocic, although in vitro studies have reported a lack of
Hydroquinone is reported to be toxic if ingested in large quantities: 1 g (equivalent to 6 – 20 g of plant material) has caused tinnitus, nausea and vomiting, sense of suffocation, shortness of breath, cyanosis, convulsions, delirium and collapse. A dose of 5 g (equivalent to 30 – 100 g of plant material) has been proved to be fatal (Herbal Medicines 2008).
Although the symptoms of overdose and
Prolonged use of Uvae ursi folium to treat urinary tract infection is not advisable since it may lead to liver damage. Patients in whom symptoms persist for longer than 48 hours should consult their doctor (Barnes et al. 2002).
Uvae ursi folium should not be used for prolonged periods. Patients with persistent symptoms of a urinary tract infection should consult a physician (WHO 2002).
Free hydroquinone could lead to hepatic impairment, especially in children after
Although consequences of
Individuals with kidney disorders (WHO 2002; British Herbal Pharmacopoeia 1996; ESCOP 2003), with irritated digestive disorders and acidic urine should not take bearberry leaf extract (Gruenwald et al. 2004).
5.6. Overall conclusions on clinical safety
Available information leads to the conclusion that bearberry leaf extract corresponding to 800 mg of hydroquinone derivatives calculated as arbutin per day used for one week can be considered as safe for human use.
Patients using bearberry leaf extract should strictly follow recommendation on dose and duration of use since there is still the possibility of mutagenic effect of hydroquinone especially on the urinary tract.
6. Overall conclusions
Bearberry leaf extract has been documented to be used for a long period of time which supports the traditional use of the herbal substance. Scientific evidence of its efficacy and safety in human is very poor and considered insufficient to support well established use of the herbal substance and extracts.
Clinical data describing pharmacology, efficacy and safety of any bearberry leaf extract or its main component arbutin are very limited and provide only basic grounds for scientific evaluation of safety and efficacy in humans.
The benefit/risk ratio can be considered positive. The
The only risk apparent from the available literature is the toxicity of hydroquinone. This substance when used in large amount has been reported to be toxic to animals and also mutagenic in some in vitro and in vivo tests. However, the amount of hydroquinone corresponding to the recommended dose of bearberry leaf extract is considered to be safe in
In conclusion, the following points should not be omitted in the benefit/risk assessment:
Hydroquinone could be naturally present in the human body. It occurs in coffee, tea or wheat cereals. In any of the presented studies, hydroquinone above 1 mg/ml was not detected in the samples. This amount is very close to the most conservative TTC1 value and together with a limited period of administration, the benefit/risk ratio can be considered positive.
Most of the animal experiments were performed in healthy animals. This is important because there is no or a very low level of pathological bacteria in urinary tract of healthy animals, resulting in very low
Administration of bearberry leaf to humans is limited to very short period and the time of exposure of human body to hydroquinone is also very limited since it is rapidly transformed to its nontoxic metabolites that are excreted via the urine.
Nevertheless, as a precautionary measure, use in pregnancy and during lactation should be avoided. The use in children and adolescents is not recommended as medical advice should be sought in this age group.
Due to inadequate data on genotoxicity, an inclusion in the Community list of herbal substances, preparations and combinations thereof for use in traditional herbal medicinal products cannot be recommended.