Blackcurrant Leaf – Ribis nigri folium (Ribes nigrum L.)

Latin name of the genus: Ribis nigri folium
Latin name of herbal substance: Ribes nigrum l.
Botanical name of plant: Herbalref.com
English common name of herbal substance: Blackcurrant leaf

Latin name of the genus: Ribis nigri folium
Botanical name of plant: Ribes nigrum L.
English common name of herbal substance: Blackcurrant Leaf

Ribis-nigri-folium - Blackcurrant Leaf at herbalref.com

Table of Contents

1. Introduction

1.1. Description of the herbal substance(s), herbal preparation(s) or combinations thereof

Herbal substance

In accordance with the European Pharmacopoeia (8th ed., 07/2013:2528) blackcurrant leaf consists of the dried leaves of Ribes nigrum L. (blackcurrant leaf). The leaf is simple, lamina is up to 10 cm long and 12 cm wide, with 3 or 5 rounded triangular lobes and the median lobe is the largest (European Pharmacopoeia 8th ed., 07/2013:2528).

Description and origin of the plant

Ribes nigrum L. belongs to the family of the Grossulariaceae. The genus Ribes contains between 140 and 150 species. The leaves are collected during or shortly after flowering (Pharm. Française 1996; Hänsel et al., 1994). A dark green upper surface and a pale greyish green lower surface is the characteristic for the slightly wrinkled leaf fragments. Furthermore, a widely spaced reticulate venation is particularly distinct on the lower surface. Glands can be seen as scattering yellowish dots. In contrast with the fresh leaves, the dried leaves have no odour or taste (Wichtl 1994; Hänsel et al., 1994).

Constituents

The dried Ribes nigrum leaf contains not less than 1% of flavonoids, expressed as isoquercitroside. The material complies with the monograph of the European Pharmacopoeia 8th ed. (2013) and British Pharmacopoeia Vol IV (2015). According to the Pharmacopée Française the dried Ribes nigrum leaf contains not less than 1.5% of flavonoids, expressed as rutin (ESCOP, 2003).

The most important secondary metabolites present in the herbal substance can be subdivided into several groups of phytochemical compounds.

Polyphenolic substances, more particularly flavonoid glycosides: kaempferol, quercetin, myricetin, isorhamnetin and sakuranetin (Wyk & Wink, 2005).

Some substances can seasonally appear in the glands of leaves of Ribes nigrum. Sakuranetin is a methylated flavanone aglycone (4’,5-diOH-7-methoxyflavanone). Its biosynthesis may be useful in the protection against parasites like Botrytis cinerea Pers. ex Fr. (Atkinson & Blakeman, 1982).

Hydroxycinnamic acid derivatives: chlorogenic acid and chlorogenic acid derivatives (isochlorogenic acid, neochlorogenic acid), caffeic acid, gallic acid, ferulic acid, coumaric acid, gentisinic acid (Trajkovski, 1974a; Trajkovski 1974b).

Prodelphinidins (proanthocyanidines) were identified in a methanolic extract of the leaves. They may be responsible for the anti-inflammatory properties of the herbal preparations (Tits et al., 1992a, 1992b).

The presence of glycerolipids has been reported. The total fatty acid composition was unusual, because the following unsaturated fatty acids were identified: linolenic acid (alpha-18:3), together with cis-7, 10, 13-hexadecatrienoic acid (16:3) and lower amounts of stearidonic acid (18:4) and gamma-linolenic acid (gamma-18:3). This makes the lipid composition type mixed: typical of 16:3 plants but also partially typical for 18:4 plants (Dobson, 2000).

The essential oil of the leaves of Ribes nigrum contains mainly monoterpenic substances like alpha- pinene, myrcene, p-cymene, limonene, beta-ocimene, beta-phellandrene, linalool, terpinen-4-ol,

geraniol, citronellylacetate. Furthermore, the sequiterpenes caryophyllene and humulene were identified, as well as methyl salicylate (Andersson et al., 1963).

Ascorbic acid, carotenoids (Herbal Medicines, 2013).

Maximum content of Ca, Mg, Fe, Al, Cr and K in the black current leaves is detected in the June (Nour et al., 2014).

The potassium-sodium ratios in the leaf of Ribes nigrum L. and decoctions of the leaves were 128:1 and 242:1 respectively. These ratios are considered as eventually contributing to the diuretic effect (Szentmihályi et al., 1998).

Herbal preparation(s)

Information about registered/authorised herbal preparations on the European market of Ribis nigri folium was provided by the National Competent Authorities and is presented in the overview of the market products, see section 2.1.1.

In France, Spain and Poland the following herbal preparation of Ribes nigrum L., folium is present as monocomponent medicinal products:

comminuted herbal substance for tea preparation

dry extract (DER: 7:1; extraction solvent water) in solid dosage form as hard capsule

powdered herbal substance in solid dosage form as hard capsule

Table 1: Information obtained from pharmacopoeias and handbooks

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.

This assessment report and the Community herbal monograph refers exclusively to Ribis nigri folium as a single ingredient. The Community herbal monograph describes the use of the comminuted herbal substance for tea preparations, powdered herbal substance in solid dosage form as hard capsule and dry extract in solid dosage form as hard capsule.

1.2. Search and assessment methodology

Electronic databases and other sources used to assess information available on traditional use, pharmaceutical, non-clinical, clinical data and current indications on Ribes nigrum L., folium using search keywords: Ribes nigrum L., Ribis nigri folium, blackcurrant leaf, cassis. No restrictions to language were set. The search of information was performed from June till September 2016.

Articles and references were retrieved from:

Scientific databases: PubMed, ScienceDirect, Scopus, Scifinder, Web of Science, EMBASE, EBSCO.

Medical databases: UpToDate.

Toxicological databases: TOXLINE.

The Cochrane Library: 1 reference was found using Ribes nigrum L., folium or blackcurrant leaf as search terms.

Libraries: hand searches in handbooks, textbooks and Pharmacopoeias on Ribes nigrum L. folium and blackcurrant leaf at the various libraries: EMA, University of Latvia, Rigas Stradinu University, The State Agency of Medicines of Latvia, National library of Latvia.

Databases of electronic books: Dawsonera.

Search engines used: Google, Google Scholar.

Other databases: The World Health Organization, National Center for Complementary and Alternative Medicine (NCCAM).

2. Data on medicinal use

2.1. Information about products on the market

2.1.1. Information about products on the market in the EU/EEA Member States

Information on medicinal products marketed in the EU/EEA

Table 2: Overview of data obtained from marketed medicinal products

This overview is not exhaustive. It is provided for information only and reflects the situation at the time when it was established.

Information on relevant combination medicinal products marketed in the EU/EEA

Hungary

Combination product

230 g of the preparation contains:

Crataegi extractum (extraction solvent red vine + alcohol): 178.71

Crataegus spp., folium cum flore

Ribes nigrum L., folium

Crataegus spp., fructus

Melissae herba

Kalium asparticum: 0.46 g

Magnesium asparticum: 0.23 g

Indication: prevention of cardiac complaints in elderly, relief of symptoms of temporary nervous cardiac complaints (e.g. palpitations, perceived extra heart beat due to mild anxiety).

All together there are six combination products containing Ribes nigrum L., folium in the old ‘healing products’ category.

Information on other products marketed in the EU/EEA (where relevant)

Latvia

The herbal preparations that contain Ribes nigrum L., folium are available on the market as food supplements (combination products).

2.1.2. Information on products on the market outside the EU/EEA

Not applicable

2.2. Information on documented medicinal use and historical data from literature

Indications exclusively in folk medicine for the Ribes nigrum leaf are: arthritis, rheumatic complaints, diarrhoea, spasmodic cough as well as it has been traditionally used as an infusion to cure joint

complaints (traditionally classified as ‘rheumatism’) (Wichtl, 1994; Leclerc 1983; Rombi, 1991). The only indication mentioned in the ESCOP monograph is ‘adjuvant in the treatment of rheumatic conditions’ (ESCOP, 2003).

Anti-inflammatory posology according to ESCOP (2003), Van Hellemont (1985) and Delfosse (1998):

Dried leaves as an infusion: from 1.5 to 4 g per cup (= 150 mL; 3-4 cups daily) to 20-50 g per litre (250 to 500 mL daily), infused during 15 minutes.

Fluid extract (1:1): 5 mL 2x daily. The extraction solvent is not specified.

Ribis nigri folium is also described in folk medicine as a diuretic, eliminating uric acid. The preparations mentioned are aqueous decoctions (Decaux, 1930; Hänsel et al., 1994).

Some authors mention the use of tea preparations containing Ribes nigrum, Fraxinus excelsior and

Ulmaria officinalis.

According to some authors, the essential oil of Ribes nigrum stimulates the renal epithelium and enhance diuresis (Garnier et al., 1961; Rombi, 1991). Rarely preparations of Ribis nigri folium were locally applied on wounds (Wichtl, 1994), as well as the leaves were applied on the head against migraine (Decaux, 1930).

Table 3: Overview of historical data

before meals.

2.3. Overall conclusions on medicinal use

According to the information provided by the National Competent Authorities in the overview of the marketed products (see section 2.1.1.), medicinal products, containing Ribes nigrum L., folium, have been available for 30 years in the markets of France, Poland and Spain therefore fulfilling the criteria of traditional use in EU in accordance with Directive 2004/24/EC.

Herbal tea (2-4 g up to 3 times daily) has been used since 1978 in Poland for minor rheumatic complaints and can be accepted according to the 30 years of use stipulated in Directive 2004/24/EC.

Powdered herbal substance in capsules has been marketed in France (since 1987) and in Spain (since 1992) in different posologies (France: 340 mg up to 5 capsules per day; Spain: 340 mg 3 times daily). At time of monograph systematic review (in 2016) the period of use fulfils the 30 years of traditional use as stipulated in Directive 2004/24/EC, therefore, this preparation can now be included in the monograph.

Dry extract (7:1; extraction solvent water) is marketed in France as capsules (169 mg per capsule; posology: up to 3 capsules daily) meets the 15-year tradition in Europe, but does not comply with the 30 years of traditional use as stipulated in Directive 2004/24/EC. Nevertheless, this preparation is included in the monograph based upon the following justification:

The extract is made with water, a procedure comparable to herbal tea preparations.

The drug-extract ratio is 7 to 1 and 169 mg is taken as a single dose up to 3 times a day. One capsule corresponds to 1183 mg of herbal substance. For herbal tea, 2 to 4 g herbal substance is infused; virtually, more material can be extracted by preparing the herbal tea. The number of daily doses is similar for the extract and the infusion.

Table 4: Overview of evidence on period of medicinal use

The use of leaves of Ribes nigrum in children and adolescents under 18 years of age is not recommended due to lack of data.

Because the HMPC could not find a suitable indication for the traditional use “to support digestive elimination”, this use was not included in the monograph.

The following indications for Ribes nigrum L., folium are proposed for the EU herbal monograph:

Traditional herbal medicinal product based upon long-standing use

Indication a): Traditional herbal medicinal product for relief of minor articular pain.

1 In the monograph this value is rounded to 170 mg

Adults and elderly:

Comminuted herbal substance for infusion as herbal tea preparation Single dose: 2 to 4 g per cup, 3 times daily.

Daily dose: 6–12 g.

Dry extract (DER 7:1, water)

Single dose: 170 mg, 1–3 times daily. Daily dose: 170–510 g.

Powder in hard capsule

Single dose: 340 mg, 3–5 times daily.

Daily dose: 1020–1700 mg (3–5 hard capsules per day)

Duration of use: 4 weeks

Indication b): Traditional herbal medicinal product to increase the amount of urine to achieve flushing of the urinary tract as an adjuvant in minor urinary complaints.

Adults and elderly:

Herbal preparations in solid dosage form: hard capsule

Dry extract (DER 7:1, water)

Single dose: 170 mg, 1–3 times daily. Daily dose: 170–510 g.

Powder in hard capsule,

Single dose: 340 mg, 3–5 times daily

Daily dose: 1020–1700 mg (3–5 hard capsules per day)

Duration of use: 2 weeks

3. Non-Clinical Data

3.1. Overview of available pharmacological data regarding the herbal substance(s), herbal preparation(s) and relevant constituents thereof

3.1.1. Primary pharmacodynamics

Analgesic effects

Ethanolic extracts

In vivo studies:

Mongold et al., (1993) reported that a Ribes nigrum L., folium extract (500 g dried leaves immersed in 15% ethanol/water in 5 L) for 10 days, then filtered and lyophilised) induced an analgesic effect in the acetic-induced writhing test in mice as well as in the Hot-plate responce test in mice.

Anti-inflammatory activity

Ethanolic extracts

In vivo studies:

Anti-inflammatory activities were observed by Mongold et al., (1993) in several in vivo models:

in the carrageenan-induced acute inflammation model Ribes nigrum L., folium extract (extraction solvent: 15% ethanol), demonstrated dose-dependent (75 and 150 mg/kg, i.p.) inhibition of acute inflammatory oedema, the effect of 150mg/kg dose was comparable to indomethacin (5 mg/kg, i.p.);

cotton pellet granuloma: Ribes nigrum L., folium extract (150 mg/kg, i.p.) inhibited granuloma formation – the relative wet granuloma weights for the control (465±19 mg), Ribes nigrum L., folium extract (351±15 mg) and indomethacin (378±8 mg);

Freund adjuvant induced arthritis: the Ribes nigrum L., folium extract (150 mg/kg – 18.71%; 300 mg/kg – 34.65%) expressed dose-dependent reduction of hind-paw oedema.

An extract of Ribes nigrum L., folium (maceration of 60 g black currant leaves with 1000 mL of 14% ethanol; 1 mL/kg and 10 mL/kg, p.o.) demonstrated anti-inflammatory activity by the inhibition of carrageenan-induced inflammation compared to reference compounds indomethacin and niflumic acid in acute and chronic studies in Sprague-Dawley rats (Declume et al., 1989).

In vitro studies:

Ribes nigrum L., folium extract (containing 60% of proanthocyanidins of the total polyphenol content) increased the CD39-positive endothelial cell fraction in a concentration-dependent manner (for the 2.5 μg/mL it increases up to 10%; for 15 μg/mL up to 33%). It also enhanced endothelial nitric oxide synthase (eNOS) activation. T495 phosphorylation was decreased by 31±6% for the dose of 2.5 μg/mL and 48±6% for 15 μg/mL, whereas S1177 phosphorylation increased by 13±3% for the dose of 2.5 μg/mL and 18±7% for 15 μg/mL compared to untreated cells (Luzak et al., 2014).

Anti-inflammatory activity of fresh Ribes nigrum L., folium extract (extraction solution: acetone/water/acetic acid (70:28:2)) was tested on the total myeloperoxidase (MPO, dose 50 ng/mL) released by activated neutrophils measured by an ELISA assay. The higher concentration (1 mg/mL) of Ribes nigrum L., folium gave about 15-20% of inhibition. MPO inhibition was also observed in a Specific Immunological Extraction Followed by Enzymatic Detection assay, Ribes nigrum L., folium extract showed a significant dose-dependent inhibition: the lowest a concentration tested, 0.5 µg/mL for leaf extract, showed 60% inhibition (Tabart et al., 2012).

Isolated constituents

In vitro studies:

Shiba et al., (2008) observed that flavonoids (quercetin, and its metabolites) inhibited the formation of dityrosine catalysed by the myeloperoxidase (MPO) enzyme in a dose-dependent manner (1.25 – 100 µM) in vitro (HL-60 cells).

The experimental model consisted of an LT2 cell line originating from human umbilical vein endothelium cells. A proanthocyanidin-enriched fraction was obtained from leaves from Ribes nigrum with acetone extraction (70% V/V in water). Purification was done on reversed phase chromatography. A significant inhibition of TNF-α (Tumor Necrosis Factor) stimulated ICAM-1 (Intercellular Adhesion Molecule 1) expression but not IL-8 and VEGF155 mRNA expression was observed with proanthocyanidins in concentrations from 10 µg/mL to 60 mg/kg (Garbacki et al., 2005).

An in vitro decrease of PGE2 production in human Chondrocytes was also observed with prodelphinidines, obtained from the Ribes nigrum L., folium, A concentration of 10-4M of gallocatechin and its dimer inhibited the formation of prostaglandins comparable with indomethacin 10-5M: 53%, 57% and 67% respectively. Further, the selectivity on COX-2 inhibition was confirmed (Garbacki et al., 2002).

Ex vivo studies:

An anti-inflammatory activity on isolated rabbit hearts was reported for rutin and isoquercitrin, obtained from the Ribes nigrum L., folium (Chanh et al., 1986).

In vivo studies:

Anti-inflammatory effects of proanthocyanidins (PACs) were observed in rat’s models of carrageenan induced paw oedema and carrageenin-induced pleurisy. Pre-treatment with PACs (10, 30, 60 and 100 mg/kg, i.p.) reduced in a dose time dependent manner paw oedema induced by carrageenin and also inhibited carrageenin-induced pleurisy in rats: particularly reducing lung injury, pleural exudate formation, polymorphonuclear cell infiltration, pleural exudate levels of TNF-α, IL-1β and CINC-1, pleural exudate levels of nitrite/nitrate (NOx). The mechanism of action of the PACs differs from that of indomethacin. Indomethacin treated rats showed that a low the volume of pleural exudate, and a reduced content in leukocytes and in TNF-α, IL-1β, IL-6 and IL-10 but not in NOx (Garbacki et al., 2004).

Garbacki et al., (2005) observed anti-inflammatory activities of proanthocyanidin-enriched fraction (PACS) of Ribes nigrum L., folium (the extraction solvent was acetone 7O% V/V in water purification by reversed phase chromatography) in Wistar rats with a dose of 10, 30 and 60 mg/kg/per animal. The following effects were observed:

a dose-dependent inhibition of the carrageen-induced pleurisy by reducing pleural exudate formation and PMNs infiltration;

leukocyte cell adhesion molecules mobilization was not down-regulated on granulocytes;

a decrease in the production of endothelial cell adhesion molecules on the lung sections.

Rodelphinidins (5, 10, 40 and 60 mg/kg) isolated from of dried Ribes nigrum L., folium extract demonstrated anti-inflammatory activities in a rat carrageenan paw oedema model by reducing paw oedema 18% for 5 mg/kg; 40% -10 mg/kg and 55% – 40 mg/kg, whereas reference compounds indomethacin 4 mg/kg reduced it by 44% and aspirin 200 mg/kg by 47% (Tits et al., 1991).

Diuretic activity

Ethanolic extracts

In vivo studies:

The model used was a salidiuretic action. The intervention consisted of oral administration of a fluidextract (extraction solvent was ethanol; 1:1) of blackcurrant leaf in rats. The diuretic action of an equivalent of 1500 mg dried leaf/kg was comparable to the effect of furosemide at 50 mg/kg (Rácz- Kotilla & Rácz 1977).

Table 5: Overview of the main non-clinical data/conclusions

3.1.2. Secondary pharmacodynamics

Antioxidative effects

In vitro studies:

The polyphenolic fraction of the water extract of Ribes nigrum L., folium (extraction solvent: water containing 200 ppm of SO2, the ratio of solvent to leaves 3:1 showed antioxidant activity, protecting the pig erythrocyte membrane against free radicals induced by UV radiation (Bonarska-Kujawa et al., 2014). In the study the effect of the extract on osmotic resistance, shape of erythrocytes was determined with spectrophotometric methods. The result suggest that the extract of Ribes nigrum L., folium protected erythrocytes against the UVC radiation, by the strengthening the membrane and inducing echinocytes (Bonarska-Kujawa et al., 2014).

The antioxidant activity of the polyphenolic (mainly flavonols) extracts of Ribes nigrum L., folium in relation to the membrane of erythrocytes and lipids extracted from red blood cell membranes (RBCL) exposed to chemical oxidizing agent 2,2′-azobis-2-methyl-propanimidamide, dihydrochloride (AAPH) was studied fluorometrically, while effects of the extracts on the properties of membranes were examined using calorimetric, IR spectroscopy and fluorimetric methods. According to the authors, the results indicate that the compounds contained in the extracts protect erythrocyte and lipid membranes against oxidation (Cyboran et al., 2014).

A spectrophotometric method was used to investigate the influence of 0.1-0.5 mg/mL of a water extract of Ribes nigrum L., folium on osmotic resistance of erythrocytes. On basis of the result the authors conclude that the extract of Ribes nigrum L., folium makes the erythrocytes less susceptible to changes in the medium tonicity and may prevent the membrane from stiffening in some pathological states (Cyboran et al., 2012).Fourteen compounds, including four 7,70-epoxylignans, three tetrahydrofuran-type sesquilignans, and a spirocyclic dilignan, isolated from the leaves of Ribes nigrum extract (dried leaves of Ribes nigrum (3.0 kg) extracted with ethanol/water (7 L x 3 kg, 70:30 V/V)) were evaluated for their antioxidant activities using superoxide anion scavenging assay and 2,2- Diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Of all the compounds tested, ribesin D and ribesin G showed the most potent superoxide anion scavenging activity with EC50 values of 1.24 and 1.12 µM, respectively (Sasaki et al., 2013).

The protective effect of two synthetic antioxidants (quercetin and caffeic acid) and 70% hydroalcoholic extract of blackcurrant leaves was tested in preventing and/or reducing the membrane lipid oxidation due to free radical attack performed by using fluorescence spectroscopy techniques. According to the authors, there results show that natural antioxidants have a much higher antioxidant activity against free radicals than synthetic compounds but they degrade after two hours of oxidation (Golea et al., 2012).

The antioxidant capacity of the blackcurrant leaf extract (1g of fresh leaves ground with 1 g of quartz in 10 mL of extraction solution: acetone/water/acetic acid (70:28:2)) was tested using several assays. Significant antioxidant activity was seen in the Trolox Equivalent Antioxidant Capacity (TEAC) assay (scavenging of the radical 2,2-azino-bis(3-ethylbenzothiazoline)-6 sulphonic acid, ABTS) – 53.7 ± 6.2 mg TE/g FW. The Cellular Antioxidant Activity (CAA) of blackcurrant leaves extracts were measured using the CAA assay on EAHy926 cells – CAA value was 12.89 ± 0.77 µmol QE/g of LE. The influence of Ribes nigrum L., folium extract on the (reactive oxygen species) ROS production of PMA-activated neutrophils was determined through a lucigenin dependent chemiluminescence assay indicating a significant dose-dependent inhibition, inducing 50% of inhibition with the concentration of 5 ± 0.5 g of leaf extract/mL (Tabart et al., 2012).

The extract (extraction solvent: water containing 200 ppm of SO2, the ratio of solvent to leaves was 3:1) of Ribes nigrum L., folium (0.005-0.05 mg/mL) exhibited an antioxidant activity. It protected the membrane lipids of pig erythrocyte against oxidation, significantly reducing the level of free radicals in erythrocyte suspension detected by the Fluorimetric and Spectrophotometric method. The antioxidant activity of the extract of Ribes nigrum L., folium is connected mainly with activity of quercetin lucosides, the extract contains about 77% of these compounds (Cyboran et al., 2011).

Anthelmintic activity

In vivo studies:

The development of free-living larvae (Oesophagostomum dentatum) was significantly inhibited by Ribes nigrum L., folium extract (acetone/water, 3:7) at different concentrations (125, 250, 500 and 1000 µg/mL) (Williams et al., 2014).

Antibacterial activity

In vitro studies:

The essential oil (obtained by hydro-distillation) from the Ribes nigrum L., folium containing Δ3-carene (18.7%), β-caryophyllene (17.7%), sabinene (11.6%), cis-β-ocimene (10.6%) and α-terpinolene (10.6%) showed the antimicrobial activity against 14 micro-organisms (including Escherichia coli, Streptococcus faecalis, Staphylococcus aureus, Candida albicans and Trichophyton mentagrophytes isolates) detected by the broth microdilution method (Stevic et al., 2010).

Antiviral effect

In vitro and in vivo studies:

Antiviral activity of a water extract (DER not specified) of Ribes nigrum L., folium (0–1 mg/mL) against influenza A virus in vitro was observed when the virus was pre-incubated prior to infection or when added directly after infection, however with no antiviral effect when infected cells were treated 2, 4, or 8 h after infection, indicating that the extract blocks a very early step in the virus infection cycle. In vivo (the C57BL/6 mouse infection model) study showed that intranasal application of the extract (500 μg) inhibits progeny virus titters in the lung up to 85% after 24 h (Haasbach et al., 2014).

Ehrhardt et al. (2013) tested a water extract (DER not specified) of Ribes nigrum L., folium against influenza A viruses infections in vitro and in vivo. The extract inhibited Influenza A virus replication in a concentration dependent (50, 100 or 200 µg/mL) manner in human alveolar type II epithelial cell line A549 model. The extract did not exert any significant negative effects on cell proliferation or survival, and did not alter transcription or translation processes (Ehrhardt et al., 2013). Ribes nigrum L., folium extract (50 and 100 µg/mL) was tested on the A549 cells using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazoliumbromide] – Cell Proliferation Assay that is based on an enzymatic reaction of the mitochondrial succinic dehydrogenase. The extract did not affect the cell morphology and viability and did not interfere with cellular proliferation and metabolism (Ehrhardt et al., 2013). In in vivo study, BALB/c mice were infected with a sub-lethal dose of influenza virus A/FPV/Bratislava/79 (H7N7). Further animals were exposed to the same extract as in vitro studies: 2 bar of aerosolized extract of Ribes nigrum L., folium (prepared from the 10 and 15 mg/mL of stock solutions) at the dose of 1.5 mL/per mouse for 10 min twice a day for three (lung titter) or five (body weight) consecutive days twice a day by using the COAALA Mouse Aerosol Application System. The results showed a reduction of virus titters in the lung of infected animals already at the day three of infection (Ehrhardt et al., 2013).

Antihypertensive effect

In vivo studies:

The model used was the antihypertensive effect on cats. Doses liquid extract (extraction solvent was ethanol; 1:1) equivalent to of 400 mg dried blackcurrant leaf/kg were compared to tolazoline 0.75 mg/kg and 1.0 mg/kg. The antihypertensive effects of both were comparable, but the effect of the leaf extract lasted for 20 minutes as compared to 5 minutes for tolazoline (Rácz-Kotilla & Rácz 1977).

In another study normotensive rats were used. An infusion of blackcurrant leaf (20 g/L) was administered intravenously at a dose equivalent to 360 mg dried leaf per kg. There was a 45% fall in blood pressure, which after 30 minutes was still 30% (Laserre et al., 1983).

3.1.3. Safety pharmacology

No data available.

3.1.4. Pharmacodynamic interactions

No data available.

3.1.5. Conclusions

Anti-inflammatory, analgesic, diuretic and antioxidative effects of Ribes nigrum L., folium extracts and isolated constituents (flavonoids, proanthocyanidins including prodelphinidines) have been demonstrated in the experimental models in vitro, ex vivo and in vivo. The preparations tested consisted mainly of alcoholic liquid extracts, which were mostly lyophilised. They were administered per orally as well as intraperitoneally.

Several inflammatory parameters have been reported reversed, especially the formation of oedema and the cellular components as illustrated by reduced exudate, infiltration of polymorph nuclear leukocytes, release of interleukins and cytokines and the formation NO-components.

Apart from the anti-inflammatory activity also an analgesic activity has been demonstrated in the acetic acid induced writhing test and the hot-plate response with mice.

The medicinal use of Ribes nigrum L., folium described in several monographs and well-known handbooks as well as indications of the products available on the EU market are supported by the effects observed in the non-clinical studies:

for the relief of minor articular pain;

to increase the amount of urine to achieve flushing of the urinary tract as an adjuvant in minor urinary complaints.

Effects reported but not related to the indications proposed for the Ribes nigrum L. folium in the monograph are antioxidative effects, antimicrobial activity, antiviral activity and antihypertensive effect.

None of the reported non-clinical pharmacological studies described indicate a cause for safety concern for the Ribes nigrum L., folium.

3.2. Overview of available pharmacokinetic data regarding the herbal substance(s), herbal preparation(s) and relevant constituents thereof

No data with regard to absorption, distribution, metabolism, elimination and pharmacokinetic interactions with other medicinal products are available.

3.3. Overview of available toxicological data regarding the herbal substance(s)/herbal preparation(s) and constituents thereof

3.3.1. Single dose toxicity

Ribes nigrum L., folium liquid extract (1:1) was administered intraperitoneally to mice. The intraperitoneal LD0 and LD50 were 22 and 49 g/kg respectively. The LD100 was estimated at 90 g/kg (ESCOP, 2003).

In another study with mice a lyophilisate obtained by maceration of 100 g leaf per litre 15% ethanol was administered. Intraperitoneal LD50 was 1.09 g/kg. Oral doses up to 3 g/kg did not show overt toxicity (ESCOP, 2003; Mongold 1993).

3.3.2. Repeat dose toxicity

Subacute toxicity

Ribes nigrum L., folium was administered to rats as a lyophilised 15% ethanolic extract (1 g of extract was equivalent to 1.8 g of leaf). The extract was administered orally in daily doses of 2 g/kg/day (21 days) and 1.34 g/kg/day (28 days) respectively. No signs of toxicity or gastric ulceration was observed (ESCOP, 2003).

Ribes nigrum L., folium was administered to rats as a lyophilisate obtained by maceration of 100 g leaf per litre 15% ethanol. The extract was administered orally during 10 days without specification of the dose. No change in feeding pattern, fluid consumption or body weight was seen. Blood analysis and histopathological evaluation of 14 organs did not reveal any abnormalities (ESCOP, 2003, Mongold, 1993).

Chronic toxicity

Feeding mice with a daily dose of 3 g/kg of dried leaves during 6 months did not reveal any toxicity (Hänsel et al., 1994).

3.3.3. Genotoxicity

No data available.

3.3.4. Carcinogenicity

No data available.

3.3.5. Reproductive and developmental toxicity

No data available.

3.3.6. Local tolerance

No data available.

3.3.7. Other special studies

The haemolytic activity of the water extract (extraction solvent water containing 200 ppm of SO2) of Ribes nigrum L., folium (at the concentrations from the 0,01 up to 0.1 mg/mL) was conducted on fresh, heparinized blood and haemoglobin concentration in the supernatant (expressed as percentage of haemoglobin concentration of totally haemolysed cells) was assumed as the measure of the extent of haemolysis. At between 0.01 and 0.1 mg/mL, the extract did not induce haemolysis but protected erythrocytes against the UVC radiation (Bonarska-Kujawa et al., 2014).

Cyboran et al., (2012) also observed that the polyphenols contained a water extract of Ribes nigrum L., folium, do not induce haemolysis in concentrations of 0.1-0.5 mg/mL. The Cellular Antioxidant Activity of Ribes nigrum L., folium (1 g of fresh leaves ground with 1 g of quartz in 10 mL of extraction solution: acetone/water/acetic acid (70:28:2)) was measured using the CAA assay on EAHy926 cells. Leaf extracts had the highest CAA value (12.89 ± 0.77 μmol QE/g of LE.

Tabart et al., (2012) performed a viability assay using MTT (3-[4,5-dimethylthiazol-2-yl]2,5- diphenyltatrazolium bromide; Cell Growth Determination Kit MTT) and found that the Ribes nigrum L., folium (1 g of fresh leaves ground with 1 g of quartz in 10 mL of extraction solution: acetone/water/acetic acid (70:28:2)) extracts (0.1 to 1 mg extract/mL) is not cytotoxic on endothelial cells.

In the range of 0.00001–1 mg/mL the water-soluble extract of Ribes nigrum L., folium showed no cytotoxic effect on three cell lines (MDCK, A549 and HeLa cells). Cytotoxicity was only observed with peripheral blood mononuclear cells (CC50 of 0.5 ± 0.3 mg/mL) the extract did not affect the proliferative status of human lymphocytes (Haasbach et al., 2014).

3.3.8. Conclusions

The data on toxicology of Ribes nigrum L., folium and relevant preparations are limited.

However, the medicinal use of Ribes nigrum L., folium is considered safe because no adverse effects have been reported during the long-standing use as a medicinal product in France, Poland and Spain.

Due to the lack of adequate data on genotoxicity a list entry cannot be proposed.

3.4. Overall conclusions on non-clinical data

The medicinal use of Ribes nigrum L., folium described in several monographs and well-known handbooks as well as of the products available on the EU market for the traditional herbal medicine is supported by the effects observed in the non-clinical (in vitro, ex vivo and in vivo data) studies:

for the relief of minor articular pain;

to increase the amount of urine to achieve flushing of the urinary tract as an adjuvant in minor urinary complaints.

Pharmacological effects not related to the indications proposed for the Ribes nigrum L., folium in the monograph are antioxidative effects, antimicrobial, antiviral and antihypertensive effect.

None of the reported non-clinical pharmacological studies described indicate a cause for safety concern for the Ribes nigrum L., folium.

The use in the European Union and available data indicate no toxicological concern and potential risks associated with Ribes nigrum L., folium use.

As there is no information on reproductive and developmental toxicity, the use during pregnancy and lactation cannot be recommended.

Tests on genotoxicity and carcinogenicity have not been performed.

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

No clinical data available.

4.1.2. Overview of pharmacokinetic data regarding the herbal substance(s)/preparation(s) including data on relevant constituents

No data available.

4.2. Clinical efficacy

4.2.1. Dose response studies

No dose response studies available.

4.2.2. Clinical studies (case studies and clinical trials)

No clinical studies reported.

4.3. Clinical studies in special populations (e.g. elderly and children)

No clinical studies in special populations reported.

4.4. Overall conclusions on clinical pharmacology and efficacy

For the Ribes nigrum L., folium no data from clinical studies are available therefore, in accordance with Directive 2001/83/EC the well-established use cannot be supported.

The traditional herbal medicinal use of Ribes nigrum L., folium for the indications which are proposed in the monograph is supported by products in the EU market and information available in several monographs, pharmacopoeias and well-known handbooks.

5. Clinical Safety/Pharmacovigilance

5.1. Overview of toxicological/safety data from clinical trials in humans

No data collected.

5.2. Patient exposure

No data available.

5.3. Adverse events, serious adverse events and deaths

No data available.

5.4. Laboratory findings

None reported

5.5. Safety in special populations and situations

5.5.1. Use in children and adolescents

The use in children and adolescents has not been investigated and is not supported by the traditional use. Therefore, the use in children and adolescents under 18 years of age is not recommended.

5.5.2. Contraindications

Oedema due to heart failure or renal insufficiency is mentioned as a possible contra-indication without any further specification (Hänsel et al., 1994; Gruenwald et al., 2000).

The monograph includes a contraindication for persons with hypersensitivity to the active substance and in conditions where a reduced fluid intake is recommended (e.g. severe cardiac or renal disease).

5.5.3. Special warnings and precautions for use

No data available. However, to exclude serious diseases and worsening of the complaints the following warnings are proposed for the monograph:

For the indication Traditional herbal medicinal product for relief of minor articular pain’:

‘articular pain accompanied by swelling of joints, redness or fever, should also be examined by a doctor’.

For the indication Traditional herbal medicinal product to increase the amount of urine to achieve flushing of the urinary tract as an adjuvant in minor urinary complaints’:

‘ if complaints or symptoms such as fever, dysuria, spasms or blood in the urine occur during the use of the medicinal product, a doctor or a qualified health care practitioner should be consulted’;

‘To ensure an increase of the amount of urine, adequate fluid intake is required during treatment’. In the revised monograph this warning/recommendation text is moved from the section ‘4.2. Posology and method of administration’ part ‘method of administration’ to the section ‘4.4. Special warnings and precautions for use’ which is considered to be more relevant section for this warning. Furthermore, this modification is also in accordance with other recently adopted EU herbal monographs for traditional herbal medicinal products’.

For both indications:

The use in children and adolescents under 18 years of age has not been established due to lack of adequate data.

If the symptoms worsen during the use of the medicinal product, a doctor or a qualified health care practitioner should be consulted.

5.5.4. Drug interactions and other forms of interaction

No data available.

5.5.5. Fertility, pregnancy and lactation

No data is available, therefore, use of Ribes nigrum L., folium cannot be recommended during pregnancy and lactation.

No fertility data available.

5.5.6. Overdose

No data available.

5.5.7. Effects on ability to drive or operate machinery or impairment of mental ability

No data available.

5.5.8. Safety in other special situations

No data available.

5.6. Overall conclusions on clinical safety

For Ribes nigrum L., folium there is no clinical safety data available. Also, the use in children or adolescents is not documented in literature.

The available information in the literature and pharmacovigilance data of marketed products do not indicate safety concerns for Ribes nigrum L., folium. As a precautionary measure a contraindication and warnings are included in the monograph.

6. Overall conclusions (benefit-risk assessment)

Due to the lack of data from clinical studies, well-established use for Ribes nigrum L., folium in accordance with Article 10a of Directive 2001/83/EC, is considered not fulfilled.

The traditional medicinal use of Ribes nigrum L., folium according to Directive 2004/24/EC is considered fulfilled based on the information available in several pharmacopoeias, relevant medicinal handbooks, and the information provided by the National Competent Authorities. The available information substantiates the presence of medicinal products on the EU market throughout a period more than 30 years, including at least 15 years within the EU. In the 2017 revision of the monograph, powdered herbal preparation was added because this preparation has been on the market in France for more than 30 years.

The traditional herbal medicinal use of Ribes nigrum L., folium for the indications and posologies which are proposed in the monograph is supported by products on the EU market, in vitro and in vivo pharmacological results and information available in several monographs, pharmacopoeias and well- known handbooks:

For oral use:

1) ‘Traditional herbal medicinal product for relief of minor articular pain’

2) ‘Traditional herbal medicinal product to increase the amount of urine to achieve flushing of the urinary tract as an adjuvant in minor urinary complaints’

The indications are considered suitable for self-medication.

There are no published reports on serious side effects with the herbal substance or herbal preparations thereof.

There are no concerns of possible drug interactions.

No data on fertility, reproductive and developmental toxicity and the usage in children and adolescents is available. Therefore, the use is not recommended in children, adolescents and during pregnancy and lactation.

A European Union list entry is not supported due to lack of adequate data on genotoxicity.

The therapeutic areas for browse search on the EMA website are ‘Pain and inflammation’ and ‘Urinary tract and genital disorders’.

No constituents with known therapeutic activity or active markers could be identified by the HMPC.

Annex

List of references