Pharmacological studies on Aristolochia papillaris Mast. (Aristolochiaceae).

The non-specific and reversible smooth muscle relaxant activities of the ethanolic extract (EE) of Aristolochia papillaris Mast., a fraction of EE containing tertiary alkaloids (TAF) and of 3 compounds isolated from TAF are reported. In the non-pregnant rat uterus, EE and TAF inhibited both the oxytocin-induced contractions and the amplitude of rhythmic spontaneous contractions. The IC50 values for EE and TAF were 0.91 and 0.22 microgram/ml, respectively in the first experiments while the corresponding values were 1.0 and 0.17 microgram/ml in the second case. The rhythmic contractions of the uterus obtained from 21-day pregnant rats were also reduced by EE and TAF with IC50 values of 25.5 and 11.2 micrograms/ml, respectively. The relaxation of isolated guinea pig trachea produced by EE and TAF were also observed with the compounds moupinamide, coclaurine and isoboldine isolated from TAF. The IC50 values of these compounds were 1.58 x 10(-4) M, 3.98 x 10(-4) M and 7.10 x 10(-4) M, respectively. Propranolol significantly antagonized the effects of coclaurine and isoboldine but failed to inhibit the responses to moupinamide which suggests that the plant constituents produce muscle relaxation by beta-adrenoceptor-dependent and -independent mechanisms.