Black Cohosh (Actaea racemosa L [formerly Cimicifuga racemosa])
Key
Constituents and Pharmacololgy
The rhizome and root are used medicinally. Active constituents include phytosterin, isoferulic acid, fukinolic acid, caffeic acid, salicylic acid, sugars, tannins, long-chain fatty acids, and triterpene glycosides: acetin, cimicifugoside, and 27-deoxyactein (recently renamed 26-deoxyactein).(3) Currently researchers feel that the triterpene glycoside fraction is the most active constituent.(10)
In a small (n=7) study of the urine of post-menopausal women who ingested single doses of black cohosh, the quinoid metabolites from the following were detected: fukinolic acid, fukiic acid, caffeic acid, and cimiracemate B, with additional quinoid metabolites from hydroxytyrosol and dihydroxyphenyl lactic acid. No potentially toxic mercapturate metabolites were detected, suggesting that reactive electrophilic metabolites are not produced in vivo.11 However, concomitant use of drugs that deplete hepatic glutathione might account for occasional reports of black cohosh hepatotoxicity.
Some controversy exists regarding the estrogenic activity of black cohosh. Part of the confusion may result from the recent finding of two different estrogen receptors.(12) Animal studies (chiefly in ovariectomized rats) show some effects suggesting estrogenic activity including transient suppression of LH.(12) In the most recent study, the researchers demonstrated inhibition of LH and partial reduction in bone mass loss in ovariectomized rats.(13) Other animal studies also suggest that black cohosh inhibits parathyroid-hormone-induced bone absorption.(12) Pharmacological effects of black cohosh in pregnancy remain unclear.(12) Some of the constituents of black cohosh appear to have anti-inflammatory effects in rats.(12) Antagonist and partial agonist activity at 5-HT1D, 5-HT1B, and 5-HT7 serotonin receptors may be responsible for alleviating menopausal symptoms, similar to SSRI antidepressants often prescribed for this indication.
In post-menopausal women, higher doses of black cohosh appeared to inhibit LH secretion, but no sustained effect on LH levels was seen at standard doses.(12) In vitro, black cohosh inhibits the stimulation of estrogen-dependent breast cancer cells and appears to have a synergistic effect when given concomitantly with tamoxifen.(14) However, the authors provided no causal data to suggest that black cohosh acted as an anti-estrogen; such high, non-physiological concentrations were used that the extracts were likely to be non-specifically cytotoxic via mechanisms not involving estrogen receptors.