© Georg Thieme Verlag Stuttgart · New York
Oxidation Products of Caffeic Acid as Model Substances for the Antigonadotropic Activity of Plant Extracts11 Dedicated to Prof. Dr. Dr. H. Witzel on the occasion of his 65th birthday
05 January 2007 (online)
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.
Caffeic acid - gonadotropins - HPGC - oxidation products - PMSG