Estrogenic activity of two standardized red clover extracts (Menoflavon((R))) intended for large scale use in hormone replacement therapy

Isoflavones, are the most potent estrogenic compounds in red clover extract s. Standardized extracts have been discussed as an alternative for hormone replacement therapy. Variation due to extraction procedure and natural seas onal variation and variations originating from agricultural conditions have prevented the large scale use of such phytochemicals. An improved extracti on procedure and careful analysis of the raw material yielded in a highly s tandardized preparation (Menoflavon((R))) with an average isoflavone conten t of approximately 9% (dry weight) determined by HPLC. The estrogenic activ ity has been further evaluated by a yeast two plasmid system using estrogen receptor alpha (ER alpha) and estrogen receptor P (ER beta). An estrogenic activity corresponding to a transactivational capacity of ca. 18 mug 17 be ta -estradiol per g red clover extract for ER alpha and ca. 78 tg 17 beta - estradiol per g red clover for ER beta was obtained. The difference is expl ained by the higher affinity of ER beta to isoflavones than that observed f or ER alpha. Calculation of potency from isoflavone content measured by HPL C yielded a comparable potency to that experimentally determined by the bio assay. The high content of isoflavones as well as the higher transactivatio nal potency for ER beta than ER alpha. make these extracts interesting cand idates for HRT. (C) 2001 Elsevier Science Ltd. All rights reserved.