Inhibition of Tumor-Promoting Effects by Poricoic Acids G and H and Other Lanostane-Type Triterpenes and Cytotoxic Activity of Poricoic Acids A and G from Poria cocos

The structures of two novel 3,4-seco-lanostane-type triterpenes isolated from the sclerotium of Poria cocos were established to be 16α-hydroxy-3,4-seco-lanosta-4(28),8,24-triene-3,21-dioic acid (1; poricoic acid G) and 16α-hydroxy-3,4-seco-24-methyllanosta-4(28),8,24(241)-triene-3,21-dioic acid (2; poricoic acid H) on the basis of spectroscopic methods. These two, and eight other known compounds isolated from the sclerotium, poricoic acid B (3), poricoic acid A (4), tumulosic acid (5), dehydrotumulosic acid (6), 3-epidehydrotumulosic acid (7), polyporenic acid C (8), 25-hydroxy-3-epidehydrotumulosic acid (9), and dehydroabietic acid methyl ester (10), showed potent inhibitory effects on Epstein−Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Evaluation of the cytotoxicity of compounds 1 and 4 against human cancer cell lines revealed that 1 was significantly cytotoxic to leukemia HL-60 cells [GI50 (concentration that yields 50% growth) value 39.3 nM], although it showed only moderate cytotoxicity to the other cells. Compound 4 exhibited moderate cytotoxicity to all of the cancer cell lines tested.