Evaluation of Venezuelan Medicinal Plant Extracts for Antitumor and Antiprotease Activities

Venezuela is a country where indigenous and local communities use more than 1500 species of plants for medicinal purposes. Anticancer drugs derived from plants may act through a direct cytotoxic effect on tumor cells or through other mechanisms such as inhibitory effects on the proteases involved in tumor growth and spread. From our databases of botanical collections and ethnobiological usage, we selected 17 species to conduct an initial survey of cytotoxicity on eight human tumor cell lines (representing lung, breast, colon, and pancreas) and activity against four proteases. Thirteen extracts from 10 species were cytotoxic, at 100 μ.g/ml or less, on one or more cell lines. Extracts of Jacaranda copaia and Tapirira guianensis were active against several cell lines, whereas extracts of Gnetum nodiflorum, Protium heptaphyllum, Protium unifoliolatum, Costus scaber, and Croton cuneatus were potent and selectively inhibitory for one or two cell lines. Antiprotease activity against one or more enzymes was detected in extracts from 14 plant species, with most activity being directed against leucine aminopeptidase (LAP). The activities observed are discussed in relation to the chemical constituents reportedly isolated from these plants and/or other species of the genus and their traditional uses.