Torilin from Torilis japonica, as a new inhibitor of testosterone 5α-reductase

The methanolic extract of the fruits of Torilis japonica showed a potent inhibition against 5α-reductase activity in vitro. Bioassay-guided fractionation of the methanol extract of the fruits followed by repeated silica gel chromatography led to the isolation of an active principle and its structure was identified as torilin on the basis of spectroscopic data. Torilin (IC₅₀ = 31.7 ± 4.23 μM) showed a stronger inhibition of 5α-reductase than α-linolenic acid (IC₅₀ = 160.3 ± 24.62 μM) but was weaker than finasteride. (IC₅₀ = 0.38 ± 0.06 μM). Simple guaiane-type compounds, such as (-)-guaiol and guaiazulene showed weak inhibitory effects on the 5α-reductase activity with IC₅₀ values of f 81.6 μM and 100.8 μM, respectively, while azulene was not active. These results suggest that both degrees of unsaturation and the side-chain in the guaiane skeleton are important for the manifestation of 5α-reductase inhibition.