Extracts from Pygeum africanum, Serenoa repens and Cucurbita pepo are used in the treatment of benign prostatic hyperplasia (BPH) and prostate cancer (PCa). The activity of the androgen receptor (AR) is known to control growth of the prostate. Here, we examined extracts of these plants for their antiandrogenic activity using an AR responsive reporter gene assay for drug discovery. A selective dichloromethane extract from the stem barks of Pygeum africanum revealed the highest antiandrogenic effect. Bioactivity-directed fractionation of this extract led to the isolation of N-butylbenzenesulfonamide (NBBS) indicating that extracts of the stem bark of P. africanum harbour androgen antagonistic activity. This compound may provide a novel approach for the prevention and treatment of BPH and human PCa.

IntroductionThe prostate gland is a part of the male reproductive system and is, normally, about the size of a walnut. Aging men will eventually develop a prostate disease at some stage of life. The most common of them are benign prostatic hyperplasia (BPH)

Extracts from Pygeum africanum are used in the treatment of prostatitis, benign prostatic hyperplasia (BPH) and prostate cancer (PCa). The ligand-activated human androgen receptor (AR) is known to control the growth of the prostate gland. Inhibition of human AR is therefore a major goal in treatment of patients. Here, we characterize the compound N-butylbenzene-sulfonamide (NBBS) isolated from P. africanum as a specific AR antagonist. This antihormonal activity inhibits AR- and progesterone receptor- (PR) mediated transactivation, but not the related human glucocorticoid receptor (GR) or the estrogen receptors (ERα or ERβ). Importantly, NBBS inhibits both endogenous PSA expression and growth of human PCa cells. Mechanistically, NBBS binds to AR and inhibits its translocation to the cell nucleus. Furthermore, using a battery of chemically synthesized derivatives of NBBS we revealed important structural aspects for androgen antagonism and have identified more potent AR antagonistic compounds. Our data suggest that NBBS is one of the active compounds of P. africanum bark and may serve as a naturally occurring, novel therapeutic agent for treatment of prostatic diseases. Thus, NBBS and its derivatives may serve as novel chemical platform for treatment prostatitis, BPH and PCa.

Inactivation of the androgen receptor (AR) through androgen ablation and treatment with antiandrogens is a major goal in the therapy for prostate hyperplasia and prostate cancer. Bioactivity-directed fractionation of a selective dichloromethane extract from the stem bark of Pygeum africanum led to the isolation of the antiandrogenic compound atraric acid. Its activity was examined by an androgen receptor responsive reporter gene assay. For lead structure optimization we transformed the natural occurring compound atraric acid into its ethyl, N-propyl and N-butyl esters and their antiandrogenic activities were examined as well. In addition, benzoic acid was isolated. The structures of all compounds were determined and characterized by means of 1H- and 13C-NMR, HR-EI-mass, IR and UV spectroscopy.