Saponin and sapogenol. XIV. Antifungal glycosides from the sea cucumber Stichopus japonicus Selenka. (1). Structure of stichopogenin A4, the genuine aglycone of holotoxin A.

Abstract

There antifungal glycosides named holotoxin A (major), B, and C were isolated from the Far Eastern sea cucumber S. japonicus Selenka. Aqueous acid hydrolysis of holotoxin A furnished genin-1 (a mixture of stichopogenin A2 and the isomer) and stichopogenin A4 (= genin-2) (3a), in addition to xylose, quinovose, 3-O-methyl-glucose and glucose, while mild methanolic acid hydrolysis of holotoxin A gave 3a and another new aglycone named 25-O-methyl-stichopogenin A4 (= genin-3) (3c). On the basis of chemical and physicochemical evidence, the structure of stichopogenin A4, the genuine aglycone of holotoxin A, was elucidated to the expressed as 3a rather than that previously proposed and the structure of 25-O-methyl-stichopogenin A4 as 3c.