Synthesis, cytotoxicity, and antioxidative activity of minor prenylated chalcones from Humulus lupulus.

The minor hop ( Humulus lupulus) chalcones 3'-geranylchalconaringenin (3), 5'-prenylxanthohumol (4), flavokawin (5), xanthohumol H (8), xanthohumol C (9), and 1'',2''-dihydroxanthohumol C (10) were synthesized. The non-natural chalcones 3'-geranyl-6'-O-methylchalconaringenin (2), 3'-methylflavokawin (6), and 2'-O-methyl-3'-prenylchalconaringenin (7) were also synthesized. Cytotoxicity was investigated in HeLa cells, and these compounds all had IC 50 values comparable to xanthohumol (8.2-19.2 microM). The ORAC-fluorescein assay revealed potent antioxidative activity for 7 and 8 with 5.2 and 4.8 Trolox equivalents, respectively.