Phytoecdysteroid constituents from Cyanotis arachnoidea

Four phytoecdysteroids that have only 19 or 21 carbons, named 11alpha-hydroxyrubrosterone (1), dihydroxyrubrosterone (2), rubrosterone (3) and poststerone (4), were isolated from the whole plant of Cyanotis arachnoidea C.B. Clarke. Among them, 1 was a new compound. Their structures were elucidated by spectroscopic methods.