D. Vanden Berghe

Screening of hundred Rwandese medicinal plants for antimicrobial and antiviral properties.

A series of 100 Rwandese medicinal plants (267 plant extracts), used by traditional healers to treat infections, were screened for antibacterial, antifungal and antiviral properties. The results of the testing showed that 45% were active against Staphylococcus aureus, 2% against Escherichia coli, 16% against Pseudomonas aeruginosa, 7% against Candida albicans, 80% against Microsporum canis and 60% against Trichophyton mentagrophytes. Not less than 27% of the plant species exhibited prominent antiviral properties against one or more test viruses, more specifically 12% against poliomyelitis, 16% against coxsackie, 3% against Semliki forest, 2% against measles and 8% against herpes simplex virus.

Proanthocyanidins in Health Care: Current and New Trends

Polyphenolic compounds are widely distributed in higher plants and are an integral part of the human diet. Recent interest in these substances has been stimulated by their potential health benefits, which are believed to arise mainly from their antioxidant activity. In the past years, the antioxidant activity of flavonoids has been studied in detail. An important but often overlooked group of polyphenols is that of the proanthocyanidins. Therefore, the present review is focused mainly on the antioxidant activity of proanthocyanidins and its relevancy in vivo. The three most important mechanisms of their antioxidant action will be discussed, i.e. free radical scavenging activity, chelation of transition metals, and inhibition of enzymes. In addition, the protective role of proanthocyanidins against lipid peroxidation and peroxynitrite, as well as their antimicrobial properties will be discussed. To study the in vivo relevancy of the proanthocyanidin activities, the knowledge of their pharmacokinetic parameters is crucial. Although bioavailability and metabolism data on polyphenols in general and proanthocyanidins in particular are still largely unavailable, the first reports indicate that at least monomers and smaller oligomeric procyanidins are absorbed. There is also considerable scientific and public interest in the important role that antioxidants may play in health care, e.g. by acting as cancer chemopreventive and anti-inflammatory agents and by reducing risk of cardiovascular mortality. Each of these aspects will be discussed, with special attention to the role of proanthocyanidins on apoptosis, gene expression and transcription factors, such as NF-kappa B.

Structure-activity relationship of flavonoids with superoxide scavenging activity.

The superoxide scavenging activities of 12 flavonoids were measured. The superoxide anions were generated by a hypoxanthine-xanthine oxidase system and measured by the nitrite method. The results showed that the scavenging ability enhanced with an increasing number of hydroxyl groups in rings B. Substitution at C3 position with a hydroxyl group increased the activity. Compared to a methoxyl group or a glycoside in this position, a free hydroxyl group showed the highest activity. A saturated C2−C3 bond showed a higher activity than a unsaturated bond. The absence of a carbonyl group at C4 position increased the activity.

Anti-microbial activity and anti-complement activity of extracts obtained from selected Hawaiian medicinal plants

Selected plants having a history of use in Polynesian traditional medicine for the treatment of infectious disease were investigated for anti-viral, anti-fungal and anti-bacterial activity in vitro. Extracts from Scaevola sericea, Psychotria hawaiiensis, Pipturus albidus and Eugenia malaccensis showed selective anti-viral activity against Herpes Simplex Virus-1 and 2 and Vesicular Stomatitis Virus. Aleurites moluccana extracts showed anti-bacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, while Pipturus albidus and Eugenia malaccensis extracts showed growth inhibition of Staphylococcus aureus and Streptococcus pyogenes. Psychotria hawaiiensis and Solanum niger inhibited growth of the fungi Microsporum canis, Trichophyton rubrum and Epidermophyton floccosum, while Ipomoea sp., Pipturus albidus, Scaevola sericea, Eugenia malaccensis, Piper methysticum, Barringtonia asiatica and Adansonia digitata extracts showed anti-fungal activity to a lesser extent. Eugenia malaccensis was also found to inhibit the classical pathway of complement suggesting that an immunological basis for its in vivo activity was identified. This study has confirmed some of the ethnobotanical reports of Hawaiian medicinal plants having curative properties against infections using biological assays in vitro.

FURTHER EVALUATION OF RWANDAN MEDICINAL PLANT EXTRACTS FOR THEIR ANTIMICROBIAL AND ANTIVIRAL ACTIVITIES

A total of 45 Rwandan plant extracts, belonging to 37 different plant species out of 21 families, were investigated for their antibacterial, antifungal, and antiviral properties. The plants were selected on the base of their ethnomedicinal use against infections and autoimmune diseases. From all the plant extracts tested, only Clematis hirsuta (leaves) showed a pronounced antifungal activity against Candida albicans and the dermatophytes Trichophyton rubrum, Epidermophyton floccosum, and Microsporum canis. Seven plant extracts showed a high antiviral activity against the DNA-virus Herpes simplex type 1, while five and three plant extracts were highly active against the RNA-viruses Coxsackie and Polio, respectively. Only Macaranga kilimandscharica (leaves) showed an interesting anti-measles activity, whereas Eriosema montanum (leaves) and Entada abyssinica (leaves) were highly active against Semliki forest virus. Some plant extracts showed an antibacterial activity against Gram-positive bacteria and Mycobacterium fortuitum, but none of them were active against the Gram-negative bacteria tested.

Antiviral ellagitannins from Spondias mombin

Two ellagitannins with antiviral properties were isolated from the leaves and stems of Spondias mombin by means of a bioguided assay. Geraniin, the main component, and galloylgeraniin, a new didehydroellagitannin, showed pronounced antiviral activity against Coxsackie and Herpes simplex viruses.

Antiviral activity of Rwandan medicinal plants against human immunodeficiency virus type-1 (HIV-1)

Hawaiian medicinal plants commonly used for the treatment of a variety of infections were screened for antiviral activity against human immunodeficiency virus type 1 (HIV-1). Sixty-one extracts derived from seventeen plants were tested for selective viral growth inhibition using the LAI (HTLV-IIIB) isolate. The greatest degree of antiviral activity was observed with aqueous extracts made from the bark of Eugenia malaccensis (L.) and the leaves of Pluchea indica (Less.) which had antiviral selectivity indices (50% cytotoxic concentration/50% effective antiviral concentration) of 109 and 94, respectively. These and other extracts conferred 100% cell protection against viral cytopathic effect when compared with control samples. Methanol and water extracts made from the Pipturus albidus (Gray) leaves and bark also achieved a high selective inhibition of virus replication with very low cytotoxicity. Plant extracts made from Aleurites moluccana (Willd.), Psychotria hawaiiensis (Gray), Clermontia aborescens (Mann), and Scaevola sericea (Forst.) also showed antiviral activity. These data provide a rationale for the characterization of antiviral natural products from these plants and related plant species.

Radical scavenging and xanthine oxidase inhibitory activity of phenolic compounds from Bridelia ferruginea stem bark

Bridelia ferruginea Benth. (Euphorbiaceae) is a subtropical medicinal plant widely used in traditional African medicine against various diseases, including rheumatic pains. Seven of its constituents (3‐O‐methylquercetin (1), 3,7,3′,4′‐tetra‐O‐methylquercetin (rutisin, 2), myricetin (3), 3′,4′,5′‐tri‐O‐methylmyricetin (ferrugin, 4), 3,3′,4′,5′‐tetra‐O‐methylmyricetin (5), quercetin 3‐O‐glucoside (6), and a biflavanol gallocatechin‐[4′‐O‐7]‐epigallocatechin (7)) have been evaluated in‐vitro in the xanthine‐xanthine oxidase enzymatic system for inhibition of xanthine oxidase and radical scavenging activity. Results indicated that compounds 1, 3, 4 and 6 exhibited, at different levels, xanthine oxidase inhibiting and superoxide scavenging activity at micromolar concentrations, whereas compound 7 showed scavenging activity only. Compounds 2 and 5 were inactive in both cases. Study of the structure‐activity relationship demonstrated that for flavonoids the xanthine oxidase inhibitory activity was reduced by methylation of the hydroxyl functionality at C‐3 and in rings A and B. These results may partly explain and support the use of B. ferruginea stem bark for the treatment of rheumatic pains in traditional medicine.

SCREENING OF SEVEN SELECTED RWANDAN MEDICINAL PLANTS FOR ANTIMICROBIAL AND ANTIVIRAL ACTIVITIES

Aqueous EtOH (80%) extracts of seven plants used by Rwandan traditional healers to treat infections, were screened for antibacterial, antifungal, and antiviral activities. Only two of the selected plants showed a true antiviral activity against herpes simplex virus type 1, while all of them exhibited virucidal properties against several enveloped viruses including herpes simplex, measles, Semliki forest, and vesicular stomatitis viruses. Four plants were diversely active against gram-positive bacteria, two of these showing bactericidal effect against the acid-fast Mycobacterium fortuitum. None of the selected plants was active against gram-negative bacteria or the yeast Candida albicans. From a bioassay-guided fractionation procedure using herpes simplex virus type I as the target model, a virucidal mixture, the maesasaponin mixture A, was isolated from the MeOH extract of Maesa lanceolata. The maesasaponin mixture A exhibited a virucidal activity against herpes simplex types 1 and 2, and vesicular stomatitis viruses.

Antiviral caffeoyl esters from Spondias mombin

Abstract Two caffeoyl esters with antiviral properties were isolated from the leaves and stems of Spondias mombin by means of a bioguided assay. 2-O-Caffeoyl-(+)-allohydroxycitric acid and chlorogenic acid butyl ester showed antiviral activities against Coxsackie and Herpes simplex viruses, respectively. The latter compound was probably an artefact formed during the isolation. Chlorogenic acid showed no antiviral activity.