The glycone portion of the glycoside of ADELOSTEMMA GRACILLIMUM Hook. f. (Asclepiadaceae) was investigated. Three known polyoxypregnane ester-type aglycones, penupogenin ( 1) (1, 2), kidjoranine ( 2) (1, 3), and gagamine ( 3) (4, 5), and one new compound named gracigenin ( 4) were isolated and their structures were characterized on the basis of spectroscopic evidence, and that of ( 4) was determined by X-ray crystallography. It was found to possess an unprecedented 8,14- SECO-polyoxypregnane ester-type skeleton, and 4 is the first compound with this C (21)-steroid type skeleton to be found in nature.