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.