EFFECT OF DESMODIUM-ADSCENDENS FRACTION-3 ON CONTRACTIONS OF RESPIRATORY SMOOTH-MUSCLE

The third flash chromatography fraction prepared from an aqueous extract of Desmodium adscendens leaves (DAF3) was evaluated for pharmacological activity using contractions of tracheal spirals and lung parenchymal strips caused by ovalbumin, arachidonic acid, histamine and carbachol. DAF3 inhibited both the early and late phases of antigen-induced contractions of both tissues dose-dependently, but had no effect on arachidonic-induced contractions. With tracheal spirals, the inhibition occurred whether the tissue was pretreated with indomethacin or not. On tracheal spirals, the maximum contraction (Emax) caused by histamine and carbachol were enhanced, but the pD2 value for histamine was not affected while that for carbachol was decreased. DAF3 had no effect on Emax or pD2 values for these agonists on lung parenchymal strips. The results suggest that DAF3 may inhibit the release of free arachidonic acid. © 1990.