ABSTRACT
Different extracts from red clover (Trifolium pratense L.) were tested for their ability to stimulate the activity of osteoblastic osteosarcoma cells (HOS58). As a key marker of osteoblasticity we chose the activity of alkaline phosphatase (ALP). Whereas butanol and methanol extracts had no influence on either ALP or cellular protein production, enzyme activity was increased significantly on incubation with chloroform extracts. All extracts were analysed for isoflavone content. The data clearly suggest a role for red clover isoflavonoids in the stimulation of osteoblastic cell activity.
Subject(s)
Alkaline Phosphatase/metabolism , Estrogens, Non-Steroidal/pharmacology , Osteoblasts/drug effects , Phytotherapy , Plant Extracts/pharmacology , Trifolium , Cell Line, Tumor/drug effects , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Estrogens, Non-Steroidal/administration & dosage , Estrogens, Non-Steroidal/therapeutic use , Humans , Osteoblasts/enzymology , Osteosarcoma/enzymology , Plant Components, Aerial , Plant Extracts/administration & dosage , Plant Extracts/therapeutic useABSTRACT
Isoflavones are the most potent estrogenic compounds in red clover extracts. Standardized extracts have been discussed as an alternative for hormone replacement therapy. Variation due to extraction procedure and natural seasonal variation and variations originating from agricultural conditions have prevented the large scale use of such phytochemicals. An improved extraction procedure and careful analysis of the raw material yielded in a highly standardized preparation (Menoflavon) with an average isoflavone content of approximately 9% (dry weight) determined by HPLC. The estrogenic activity has been further evaluated by a yeast two plasmid system using estrogen receptor alpha (ER alpha) and estrogen receptor beta (ER beta). An estrogenic activity corresponding to a transactivational capacity of ca. 18 microg 17 beta-estradiol per g red clover extract for ER alpha and ca. 78 microg 17 beta-estradiol per g red clover for ER beta was obtained. The difference is explained by the higher affinity of ER beta to isoflavones than that observed for ER alpha. Calculation of potency from isoflavone content measured by HPLC yielded a comparable potency to that experimentally determined by the bioassay. The high content of isoflavones as well as the higher transactivational potency for ER beta than ER alpha make these extracts interesting candidates for HRT.
