The in vitro study, published in Phytomedicine , looked at extracts and compounds from black cohosh and related Cimicifuga species and found that the potential anti-cancer benefits were related to the triterpene glycoside content.
The study adds to a small but growing body of research suggesting breast cancer prevention for a herb most commonly used by women to reduce menopausal symptoms such as hot flushes.
Black cohosh (referred to by the European Medicines Agency, or EMEA, as Cimicifugae racemosae rhizome) is a member of the buttercup family, and is a perennial plant native to North America.
Lead author Linda Saxe Einbond from Columbia University, in collaboration with researchers from Jinan University and Naturex, investigated the effects of black cohosh fractions enriched for triterpene glycosides and purified components from the herb against the human breast cancer cell line MDAMB-453.
The researchers report that the most potent component tested was 25-acetyl-7,8-didehydrocimigenol 3-O-b-D-xylopyranoside.
The IC50 value, a measure of the extract concentration under which 50 per cent of the cell population growth was inhibited, was 3.2 micrograms per millilitre (ug/ml).
This compared favourably with the parent compound (7,8-didehydrocimigenol 3-O-b-D-xylopyranoside) that had an IC50 value of 7.2 ug/ml.
"Thus, the acetyl group at position C-25 enhances growth inhibitory activity," wrote the researchers.
They note that the inhibition of growth was related to an induction of programmed cell death (apoptosis).
The black cohosh extracts containing one, 15 and 27 per cent triterpene glycosides were provided by Naturex.
The study was funded by the National Institutes of Health (NIH) and the Susan G. Komen Breast Cancer Foundation.
"These results corroborate the results of our previous studies indicating that the growth inhibitory effect of actein or an extract of black cohosh is associated with activation of specific stress response pathways and apoptosis," wrote the researchers, referring to their studies published earlier this year in Anticancer Research (Vol. 2, pp.
697-712) and the International Journal of Cancer (Vol. 121, pp. 2073-2083).
"Taken together, these results indicate that the triterpene glycoside actein and related compounds may be useful in the prevention and treatment of human breast cancer," they concluded.
The research was welcomed by Jacques Dikansky, president and C.E.O. of Naturex: "Over one million women worldwide are diagnosed with breast cancer every year.
We are proud to contribute to scientific efforts to fight this disease."
Although these results are promising, further scientific research is needed to determine whether the herb could be considered a breast cancer chemopreventive agent.
Previously, concerns have been raised about breast cancer patients taking black cohosh supplements in order to alleviate the menopause-like side effects.
Researchers from Yale School of Medicine reported that black cohosh might interact detrimentally with chemotherapy by increasing cytotoxicity (cell killing) by two of the drugs, doxorubicin and docetaxel.
It decreased the cytotoxicity of cisplatin.
Over one million women worldwide are diagnosed with breast cancer every year, with the highest incidences in the US and the Netherlands.
China has the lowest incidence and mortality rate of the disease.
Black cohosh has historically been a popular alternative to hormone replacement therapy (HRT) in many countries including the UK, where it is estimated that 9 million days worth of black cohosh supplements were purchased in 2004.
Source: Phytomedicine (Elsevier) Published on-line ahead of print 5 November 2007, doi: 10.1016/j.phymed.2007.09.017 "Growth inhibitory activity of extracts and compounds from Cimicifuga species on human breast cancer cells" Authors: L. Saxe Einbond, Y. Wen-Cai, K. He, H.-a.
Wu, E. Cruz, M. Roller and F. Kronenberg