Effects of natural products on the inhibition of 5α-reductase type 2 for the development of chemopreventive agents in LNCaP cells

Abstract

The enzyme steroid 5α-reductase is responsible for the conversion of testosterone into the most potent androgen dihydrotestosterone (DHT). In man, this steroid acts on a variety of androgen-responsive target tissues to mediate such diverse endocrine processes as male sexual differentiation in the fetus and prostatic growth in men. Androgen levels in the prostate may influence carcinogenesis in this organ. The use of a 5α-reductase inhibitor, finasteride, in the chemoprevention of prostate cancer is being evaluated in a clinical trial and have been used successfully for treatment of benign prostatic hyperplasia. Therefore, for the discovery of 5α-reductase type 2 inhibitors, we have evaluated the inhibitory effects of solvent fractionated extracts of natural products on 5α-reductase type 2 activity. We have tested approximately 80 kinds of natural products after partition into n-hexane, ethyl acetate and aqueous layer from 100% methanol extracts of plants. The ethyl acetate fractions of Perilla sikokiana (seed, IC50 : 6.2 ug/ml), Sophora flavescens (root, IC50 : 8.9 ug/ml), and Angelica tenuissima (root, IC50 : 11.7 ug/ml) revealed inhibitory effects on 5α-reductase 2 activity in LNCaP cells. The effective ethyl acetate fractions of Perilla sikokiana, Sophora flavescens, Hydnocarpus anthelmintica, and Angelica tenuissima were subfractionated by column chromatography and tested. The subfractions F4 (IC50 : 1.1. ug/ml), F5 (IC50 : 2.0 ug/ml), and F6 (IC50 : 5.8 ug/ml) of the ethyl acetate fraction of Perilla skikokiana and the subfraction F8 (IC50 : 5.3 ug/ml) of the ethyl acetate fraction of Sophora flavescens displayed greater inhibition of 5α-reductase type 2 than did finasteride in LNCaP cells. These active fractions are under the process of further sequential fractionation to find the effective pure compounds against 5α- reductase 2 activity.