Two new triterpenes from the rhizome of Dryopteris crassirhizoma, and inhibitory activities of its constituents on human immunodeficiency virus-1 protease

Two new hopane type triterpenes, named dryopteric acids A (1) and B (2), were isolated from the Rhizome of Dryopteris crassirhizoma (Aspiadaceae) together with sixteen known compounds (3-18). Of isolated compounds, ursolic acid (15), and dryopteric acid A (1) and B (2) showed potent inhibitory activities against HIV-1 protease with IC50 values of 8.9-44.5 mu m. In addition, acetylated compounds 1 and 2 appreciably increased inhibitory activities with their IC50 values of 1.7 and 10.8 mu m, respectively.