SYNTHESIS AND ANTIFUNGAL ACTIVITY OF MEDICAGENIC ACID SAPONINS ON PLANT-PATHOGENS - MODIFICATION OF THE SACCHARIDE MOIETY AND THE 23-ALPHA SUBSTITUTION

The study of structure-antifungal activity relationships of medicageni c acid saponins was widened to include synthetic glycosides of mannose , galactose, cellobiose, and lactose as well as a 23alpha-hydroxy-meth yl analog of medicagenic acid, namely, methyl hydroxymethyl-DELTA12-ol eanene-28beta-carboxylate, against Sclerotium rolfsii, Rhizoctonia sol ani, Trichoderma viride, Aspergillus niger, and Fusarium oxysporum. Th e native glucose-containing saponin was a more effective antifungal ag ent than the aforementioned saponins, except in the case of the cellob iose-containing derivative and F. oxysporum. A carboxyl substituent at the 23alpha position of the sapogenin brought about higher fungistati c activity than a methyl carboxylate which, in turn, was more effectiv e than an hydroxymethyl group at the same position.