CUCURBIC ACID AND ITS 6,7-STEREOISOMERS

The derivatives 7-iso-cucurbic acid (7-iso-CA) and 6-epi-7-iso-cucurbic acid (6-epi-7-iso-CA) were prepared from (-)-jasmonic acid (JA) by reduction and cucurbic acid (CA) and 6-epi-cucurbic acid (6-epi-CA) from (+)-7-iso-jasmonic acid (7-iso-JA). The chromatographic properties (TLC, HPLC, GC) of these derivatives are described and the structures established by physical data. The extracts of different plant materials were analysed with respect to the natural occurrence of JA and CA and its 6,7-stereoisomers. JA, 6-epi-CA and 6-epi-7-iso-CA were identified in female flowers of Juglans regia and JA, CA, 6-epi-CA and 6-epi-7-iso-CA in spores of Anemia phyllitidis. JA, CA, 6-epi-CA and 9,10-dihydro-JA were detected in immature caryopses of Secale cereale. In rye JA dominated in young caryopses, while CA level exceeded the amount of JA in the premature fruits. In each tissue 6-epi-CA was found to be a minor component, while CA or 6-epi-7-iso-CA represented the major components; 7-iso-CA could not be detected.