Acacia concinna Saponins. II. Structures of monoterpenoid glycosides in the alkaline hydrolysate of the saponin fraction

Abstract

From the AcOEt-soluble fraction of the alkaline hydrolyzate of the highly polar saponin fraction of pods of Acacia concinna, two monoterpenes, (2E)-2,6-dimethyl-6-hydroxy-2,7-octadienoic acid (menthiafolic acid, 1) and (2E)-6-hydroxy-2-hydroxymethyl-6-methyl-2,7-octadienoic acid (4), and their glycosides, (6R)- and (6S)-menthiafolic acid-6-O-β-D-quinovoside (2a and 2b) and (6R)- and (6S)-menthiafolic acid-6-O-β-D-xyloside (3a and 3b), were isolated. A more polar fraction gave, after methylation with diazomethane, (6R)- and (6S)-(2E)-6-hydroxy-2-hydroxymethyl-6-methyl-2,7-octadienoic acid- 6-O-β-D-quinovoside as their methyl esters (5a and 5b). Compounds 2a, 3a, 4, 5a, and 5b are new. The structures of the above compounds were determined mainly by the application of spectroscopic methods.