EFFECTS OF THE SABAL-SERRULATA EXTRACT IDS-89 AND ITS SUBFRACTIONS ON5-ALPHA-REDUCTASE ACTIVITY IN HUMAN BENIGN PROSTATIC HYPERPLASIA

Extracts from fruits of Sabal serrulata are used in the treatment of h uman benign prostatic hyperplasia (BPH). Therefore, it is of interest whether this phytopharmacon has any influence on the androgen metaboli sm in the human prostate. It was found that the extract IDS 89 of Saba l serrulata inhibited dose dependently 5 alpha-reductase activity in t he epithelium and stroma of human BPH, the mean inhibition being 29% a nd 45%, respectively. This inhibitory effect is mainly due to the sapo nifiable subfraction of IDS 89 showing a mean 5 alpha-reductase inhibi tion of 39% and 38% in epithelium and stroma, respectively. The inhibi tion was dose dependent and noncompetitive. At a testosterone concentr ation of 580 nM as substrate for 5 alpha-reductase, the main fatty aci ds of the extract IDS 89 gave rise to a percentual enzyme inhibition i n the epithelium and stroma as follows: 51% and 42% (lauric acid), 5% and 0% (oleic acid), 43% and 34% (myristic acid), 2% and 0% (palmitic acid), respectively. The inhibitory effect of lauric acid was noncompe titive and dose dependent up to a concentration of 0.2 mM, the maximal inhibition in the epithelium and stroma being 52% and 45%, respective ly. The nonsaponifiable subfraction, consisting mainly of phytosterols , showed a mean inhibition of 5 alpha-reductase in the epithelium and stroma of 15% and 10%, respectively. Finally, the hydrophilic subfract ion, containing carbohydrates, amino acids, and polysaccharides, showe d no inhibitory effect. The present in vitro studies suggest that the Sabal serrulata extract IDS 89 has an inhibitory effect on 5 alpha-red uctase in the epithelium and stroma of human BPH. This inhibition is m ainly due to the fatty acids of the saponifiable subfraction. (C) 1996 Wiley-Liss, Inc.