Etude de l'activite biologique des plantes medicinales de la flore rwandaise: Maesa lanceolata Forsskal var. golungensis Welw. et Ipomoea involucrata P. Beauv

The plants used in folk medicine possess real therapeutical properties and have been an important source of drugs for a long time. They offer excellent perspectives for the discovery of new pharmaceutical drugs, in particular anti-infectious agents. Furthermore, the majority of the Rwandan population, like elsewhere in the Third-World, are dependent on traditional medicine for their primary health care. These facts prompted us to undertake a study on the antiviral activity of seven plants, currently used by Rwandan healers.; In a preliminary antiviral screening against a battery of six viruses (enveloped and non-enveloped viruses), Maesa lanceolata and Ipomoea involucrata exhibited an interesting antiviral activity against enveloped viruses. In a bioassay-guided purification using HSV 1 as target model, two virucidal saponin mixtures against HSV 1, HSV 2 and VSV T2 were isolated from M. lanceolata, whereas an antiherpetic (HSV 1 and 2) glycosidic resin and two non-identified fractions showing a moderate anti-HIV activity were obtained from I. involucrata. The saponin mixture MC3B1 showed a potent haemolytic and molluscicidal activity but also mild fungistatic and antimutagenic effects. The sapogenine mixture obtained upon acidic hydrolysis of MC3B1 was not active. The combination of both saponin mixtures as found naturally in M. lanceolata, showed higher virucidal activity than either of the mixtures separately. MC3B1 contains six homologous oleanan type saponins, characterized by MS, {dollar}sp1{dollar}H-, {dollar}sp{lcub}13{rcub}{dollar}C- and 2D-NMR. The glycosidic resin (IEY2B5A) isolated from I. involucrata exerted a high true antiviral activity against HSV 1 and HSV 2. To our knowledge, such an activity has not been reported yet for this class of compounds. The fractions IDZ1 and IDZ2 exhibited moderate anti-HIV activity. The saponins from M. lanceolata as well as the glycosidic resin from I. involucrata have significant cytotoxicity, while IDZ1 and IDZ2 show a reasonable selectivity.; Haemolyzing saponins are regarded as useful oral hypocholesterolaemic agents, suggesting that MC3B1 could find a possible clinical application. Like aescine, MC3B1 could be used as anti-oedematious in the treatment of symptoms related to the veino-lymphatic system failure. M. lanceolata would, in addition, play a major role in schistosomiasis prevention by a local control of the aquatic snail vector. Glycosidic resins from Convolvulaceae have been reported to show an antitumor activity, like most true antivirals. I. involucrata resin is worth being tested for that interesting property.