抄録
Two new kaurenolides A and B, four new gibberellins C, D, E and F, and plant growth-inhibitory factors G, H, I, J, K, L, M, N and O have been isolated from seeds of pumpkin (Cucurbita pepo L.). Their structures have been elucidated on the basis of spectral data and chemical evidences. On the rice seedling assay, A, B, D (GA_<39>) and E were inactive, while F, an epimer at C-12 of E, was active. I and J completely inhibited the growth of rice seedlings at a concentration of 10^<-3>M. M, named cucurbic acid, and its derivatives N and O inhibited the growth of rice and lettuce seedlings at a concentration of 10^<-3>M, but showed no effect on Avena coleoptile assay. A possible biosynthetic pathway of cucurbic acid is discussed, and jasmonic acid could be biosynthesized from cucurbic acid by oxidation of the hydroxyl group at C-6 followed by epimerization at C-7.
