“…For example, didehydrostemofoline, a protostemonine-type alkaloid from S. collinsa, was found to have high insect toxicity with an LC 50 value as low as 0.8 ppm, which was significantly more potent than that of the well-known natural insecticide azadirachtin with an LC 50 8.2 ppm (Brem et al, 2002). Our laboratory has investigated the chemistry and antitussive activities of Stemona alkaloids (Chun et al, 2003;Jiang et al, 2002Jiang et al, , 2006aXu et al, 2006;Xu, 2006;Zhou et al, 2006), and discovered four chemical types of variations of S. tuberosa, characterized by croomine, stemoninine, neotuberostemonine, or tuberostemonine (Jiang et al, 2006a). Furthermore, the total alkaloid compositions of these four chemotypes of S. tuberosa were found to exhibit different degrees of antitussive properties in the citric acid-induced guinea-pig cough model .…”