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 IC50 values comparable to xanthohumol (8.2−19.2 μM). The ORAC-fluorescein assay revealed potent antioxidative activity for 7 and 8 with 5.2 and 4.8 Trolox equivalents, respectively.
Susanne Vogel and Jörg Heilmann