Phytochemical studies on Stemona plants: biological activities of some stemofoline alkaloids

The Stemona family of alkaloids includes more than seventy different natural products that have been structurally classified into eight different groups including stemofine. Many pure alkaloids derived from the extracts of the leaves and roots of Stemona species have insect toxicity, antifeedent and insect repellent activities and antitussive activities. We report here the biological activities i.e. antiinsect activities (bioautography) and antimicrobial activities of some stemofoline alkaloids including (3'R)-stemofolenol (1), (3'S)-stemofolenol (2), (3'R)-hydroxystemofoline (3) and (3'S)-hydroxystemofoline (4). All of tested substances showed antiinsect property. 4 showed the highest acetylcholinesterase inhibition at <50ng followed by 1, 2 and 3 with <100, <200 and <200ng of inhibition, respectively. For antimicrobial activity against Ps. alruginosa, 1 and 3 gave better efficiency with the MIC of 62.5 ppm followed by 2 and 4 at 125 ppm compared to gentamycin at 1.953 ppm. For antimicrobial against S. aureus, 1 and 2 were more effective with the MBC of 125 ppm followed by 3 and 4 at 250 ppm compared to gentamycin at 3.906 ppm.