NEW BIOACTIVE ORGANIC-COMPOUNDS FROM TURKISH MEDICINAL-PLANTS

Turkey has a very rich flora and a long history of herbal medicine pra ctices. The biological evaluation of substances from plant sources is highly relevant for the identification of lead compounds which can res ult in the development of novel and safe medicinal agents. During our extensive studies with Turkish medicinal plants, we have isolated and characterized a large number of natural products. Although Turkey is e ndowed with a wide variety of medicinal plants, very little effort has been made so far towards bioassay-directed isolation of biologically active compounds from indigenous plants. During the past few years, we have also been engaged in the isolation and structure elucidation of compounds through a bioassay-directed fractionation procedure. In this manuscript, new bioactive steroidal alkaloids isolated from Buxus, Ve ratrum and Fritillaria species are presented. Among these, four steroi dal alkaloids isolated from the leaves of Buxus longifolia have shown significant antibacterial activity against Salmonella typhi, Shigella flexneri, Escherichia coli and Pseudomonas aeruginosa. Three steroidal alkaloids from Veratrum album have been shown to have antihypertensiv e actions. In addition, a new steroidal base obtained from the bulbs o f Fritillaria imperialis exhibited anticholinergic activity as manifes ted by the blockade of acetylcholine responses on isolated guinea-pig ileum and atria.