The 50% ethanol extracts from Resina Pini of Pinus sp. (Pinaceae) showed more potent inhibitory activity against testosterone 5α-reductase prepared from rat prostate than those from several medicinal plants used for the treatment of androgen-dependent diseases such as benign prostatic hyperplasia. The fraction responsible for this activity was purified, and the active constituent was isolated and identified as abietic acid, a diterpene resin acid, which exhibited potent testosterone 5α-reductase inhibitory activity. Methyl abietate was substantially inactive against testosterone 5α-reductase, whereas other diterpene resin acids, pimaric acid and neoabietic acid, were as active as abietic acid against testosterone 5α-reductase, indicating that the negatively charged anionic carboxyl group on the molecule is an important structural moiety for the inhibitory activity. These findings suggest that a nonsteroidal anionic diterpene compound of natural origin may have the potential to act as a transition state analogue inhibitor of testosterone 5α-reductase in the treatment of androgen-dependent diseases.
2010 by The Pharmaceutical Society of Japan