Phytochemistry and biological activities of selected Colombian medicinal plants

This thesis deals with the search for antibiotic compounds in medicinal plants traditionally used in the treatment of skin morbid conditions by First Nations People in Colombia. The plant collection was carried out in four culturally and geographically different regions of Colombia. Twenty-four chemical plant extracts were screened against different Gram positive and Gram negative bacteria, yeast and viruses. The plant extract from Piper lanceaefolium exhibited good activity against the yeast Candida albicans and the one from Iryanthera megistophylla displayed very good activity against herpes simplex virus and Staphylococcus aureus MS (methicillin-sensitive). Four compounds, not described in the literature, were isolated and further characterised from Piper lanceaefolium. Phytochemical analyses of Iryanthera megistophylla carried out by Dr. Dong Sheng Ming led to the isolation of two new compounds and seven known compounds. Amongst the known compounds a flavolignan, iryantherin K, presented potent activity against Staphylococcus aureus MS (methicillinsensitive) and more importantly against Staphylococcus aureus MR (methicillinresistant). Iryantherin K and its stereoisomer iryantherin L also exhibited good inhibition of the Candida albicans secreted aspartic protease, which is a virulent factor in Candida infections. The therapeutic potential that is offered by iryantherin K justifies a further toxicological and pharmacological assessment in animal models.Science, Faculty ofBotany, Department ofGraduat