Extract from fruit of Sabal serrulata are used in the treatment of human benign prostate
hyperplasia (BPH). Therefore, it is of interest whether this phytopharmacon has any influence on the
androgen metabolism in the human prostate. It was found that the extract
IDS 89 of Sabal serrulata inhibited dose dependently
5 alpha-reductase activity in the epithelium and stroma of human BPH, the mean inhibition being 29% and 45%, respectively. This inhibitory effect is mainly due to the saponifiable subfraction of
IDS 89 showing a mean
5 alpha-reductase inhibition of 39% and 38% in epithelium and stroma, respectively. The inhibition was dose dependent and noncompetitive. At a
testosterone concentration of 580 nM as substrate for
5 alpha-reductase, the main
fatty acids of the extract
IDS 89 gave rise to a percentual
enzyme inhibition in 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 noncompetitive and dose dependent up to a concentration of 0.2 nM, the maximal inhibition in the epithelium and stroma being 52% and 45%, respectively. 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 subfraction, containing
carbohydrates,
amino acids, and
polysaccharides, showed no inhibitory effect. The present in vitro studies suggest that the
Sabal serrulata extract IDS 89 has an inhibitory effect on
5 alpha-reductase in the epithelium and stroma of human BPH. This inhibition is mainly due to the
fatty acids of the saponifiable subfraction.