The role of the lignan constituents in the effect of Schisandra chinensis fruit extract on penile erection.

The effect of the ethanol extract and active components of the fruit of Schisandra chinensis was evaluated on rabbit penile corpus cavernosum (PCC). PCC, pre-contracted with 10(-5)  m phenylephrine (Phe), was treated with extracts of S. chinensis at five different compositions of ethanol and water (95%, 70%, 50%, 30% and ethanol/water [v/v]) and three fractions (0.1, 0.5, 1 and 2 mg/mL). The effect of the extracts and active lignans (schisandrol A and schisandrol B) from S. chinensis on sildenafil citrate pre-incubated PCC was also evaluated. The PCC relaxation induced by the 95% ethanol extraction and the n-hexane fraction was concentration-dependent and the ethanol extract enhanced sildenafil citrate-induced PCC relaxation. The active components of S. chinensis (schisandrol A and schisandrol B) significantly enhanced sildenafil citrate-induced relaxation >2-fold; schisandrol A had the highest relaxant effect on sildenafil citrate pre-incubated PCC. The lignans, schisandrol A and schisandrol B, isolated from the fruits of S. chinensis enhanced sildenafil citrate-induced relaxation and may have synergistic action in patients who do not completely respond to sildenafil.