New prenylchalcones from the hops of Humulus lupulus

Two new prenylchalcones, xanthohumol C and D, together with two known prenylchalcone derivatives, xanthohumol (1) and 5 ''-(2 ''-hydroxyisopropyl)-dihydrofurano-[2 '',3 ''-b]-4,4'-dihydroxy-6'-methoxy-chalcone (4) were isolated and identified from the hops of Humulus lupulus L. The structures of xanhohumol C and D were elucidated as 5 ''-hydroxy-6 '',6 ''-dimethyl-dihydropyrano-[2 '',3 ''-b]- 4,4'-dihydroxy-6'-methoxy-chalcone (2) and 5 ''-hydroxy-'' 6,6 ''-dimethyl-dihydropyrano-[2 '',3 ''-b]-4',6'-dimethoxy-4-hydroxy-chalcone (3) on the basis of HRFAB-MS, 1D and 2D NMR (HMQC, HMBC) spectroscopic data. Among the new prenylchalcones, compound 2 showed marginal cytotoxic activity against human stomach carcinoma BGC-823 and human hepatic carcinoma HepG2 cells.