Abstract
Phenolic plant constituents exert antigon-adotropic activity following an oxidation.
The resulting complex mixture of mostly instable products impedes the elucidation
of the various oxidation steps as well as the mode of antigonadotropic action. Thus
caffeic acid was chosen as a single model phenolic to facilitate the interpretation.
The oxidation of caffeic acid with KMn04 as well as with polyphenoloxidase leads to
the instable caffeic acid o-quinone as the first oxidation product. Following the initial oxidation, a number
of products was in dicated via HPLC. Two of them were isolated and characterized as
oligomers of caffeic acid, one of them with phenolic, acid and, quinoic structural
components and a relative molecular mass similar to caffeic acid tetramer.
It was shown that caffeic acid quinone cannot be the antigonadotropically active principle.
Correspondingly, the isolated oxidation products exhibit pronounced antigonadotropic
activity. It could be proved that oxidation products of caffeic acid bind to PMSG,
forming PMSG-inhibitor-complexes. In such complexes the gonadotropic activity of PMSG
is completely abolished.
Key words
Caffeic acid - gonadotropins - HPGC - oxidation products - PMSG
