Inhibition of 5α-reductase in the rat prostate by Cimicifuga racemosa

ObjectivesProstate cancers and many thereof derived cell lines, as the LNCaP cells, grow androgen-dependent. In vivo testosterone is locally converted by 5α-reductase to 5α-dihydrotestosterone (5α-DHT) which is the major androgenic principle in prostates and seminal vesicles. The occurrence of prostate cancer and growth of LNCaP cells can be effectively inhibited by finasteride, a synthetic 5α-reductase inhibitor and by a black cohosh (Cimicifuga racemosa, CR) extract. In the present contribution we tested whether the aqueous/ethanolic C. racemosa extract BNO 1055 contains 5α-reductase inhibitors.MethodsImmature 24-day-old male rats were fed with testosterone (T)-containing food and injected with 30 mg CR BNO 1055 or 0.5 mg finasteride for 5 days. Average daily T-uptake was 39 mg/animal. Other animals remained untreated or received vehicle injections only.ResultsIn comparison to totally untreated rats the testosterone treatment increased weight of prostates and seminal vesicles 3–5-fold and this proliferation was largely and equipotently inhibited by finasteride and CR BNO 1055. 5α-Dihydrotestosterone concentrations in prostate tissue extracts were also reduced by both compounds and the testosterone-upregulated androgen receptor and insulin like growth factor I gene expression inhibited in the seminals vesicles.ConclusionTaken together, these results indicate that the CR extract BNO 1055 contains one or more potent 5α-reductase inhibitors which may make this extract suitable for the prevention and treatment of prostate cancer and possibly of benign prostate hyperplasia (BPH).