Antisweet Natural Products. IX. Structures of Gymnemic Acids XV-XVIII from Gymnema sylvestre R. BR. V.

Systematic separation of the saponin fraction of the leaves of Gymnema sylvestre has led to the isolation of four new saponins, gymnemic acids XV-XVIII, as antisweet substances. The structures were elucidated by spectral and chemical studies. Gymnemic acids XV-XVIII, are 21-O-2-methylbutyryl-22-O-2-methylcrotonoyl, 16, 22-O-bis-2-methylcrotonoyl, 21-O-benzoyl, and 28-O-benzoyl gymnemagenin 3-O-gluculonides, respectively. Gymnemic acids VIII and...