Abstract
Biological activity of intermediate steroids in the biosynthesis of brassinolide was examined by the rice-lamina inclination test and wheat-leaf unrolling test. In both bioassays, biological activity of intermediates increased according to the order in the biosynthetic pathway. The introduction of a hydroxyl group in the side chain (C-22), the step of 6-oxocampestanol to cathasterone, strikingly enhanced the activity. The activities of teasterone, 3-dehydrotea-sterone, and typhasterol were almost the same. Relative activities in the rice-lamina inclination test were as follows : 6-oxocampesta-nol (0. 002), cathasterone (1), teasterone (20), castasterone (240), and brassinolide (1200).
