Chemical Constituents of Aristolochia constricta: Antispasmodic Effects of Its Constituents in Guinea-Pig Ileum and Isolation of a Diterpeno−Lignan Hybrid

Twenty constituents were isolated from the n-hexane and chloroform extracts of Aristolochia constricta, a plant whose aerial parts have been used empirically in folk medicine for various purposes. The inhibitory effects of these constituents on smooth muscle contraction in isolated guinea-pig ileum were studied in order to observe their antispasmodic effects. 3,4-Dibenzyldihydrofuran-type lignans [(−)-cubebin, (−)-hinokinin, and (−)-pluviatolide] and a kaurene-type diterpene [(−)-kaur-16-en-19-oic acid] were isolated as active principals. They inhibited electrically induced and acetylcholine-induced contraction in the isolated guinea-pig ileum. In addition, 9-O-[(−)-kaur-15-en-17-oxyl]cubebin was isolated as a new diterpeno−lignan hybrid, although this constituent did not exhibit antispasmodic activity.