Chitin synthase II inhibitory activity of ursolic acid, isolated from Crataegus pinnatifida

Two triterpenoid compounds, ursolic acid and uvaol, were isolated from Crat aegus pinnatifida Bunge leaves. Ursolic acid inhibits chitin synthase II fr om S. cerevisiae with an IC50 value of 0.84 mu g/ml and the inhibition appe ars to be selective for chitin synthase II, whereas uvaol has no inhibitory activity up to 280 mu g/ml. Oleanolic acid, alpha-hederin hydrate, and bet ulic acid inhibited the chitin synthase II activity under the same conditio ns with an IC50 of 5.6, 64.3, and 98.7 mu g/ml, respectively.