The endocrine activities of 8-prenylnaringenin and related hop (Humulus lupulus L.) flavonoids

The female flowers of the hop plant have long been used as a presentative a nd a flavoring agent in beer, but they are now being included in some herba l preparations for women for "breast enhancement". This study investigated the relative estrogenic, androgenic and progestogenic activities of the kno wn phytoestrogen, 8-prenylnaringenin, and structurally related hop flavonoi ds. 6-Prenylnaringenin, 6,8-diprenylnaringenin and 8-geranylnaringenin exhi bited some estrogenicity, but their potency was less than 1% of that of 8-p renylnaringenin. 8-Prenylnaringenin alone competed strongly with 17 beta -e stradiol for binding to both the alpha- and beta -estrogen receptors. None of the compounds (xanthohumol, isoxanthohumol, 8-prenylnaringenin, 6-prenyl naringenin, 3'-geranylchalconaringenin, 6-geranylnaringenin, 8-geranylnarin genin, 4'-O-methyl-3'-prenylchalconarinagenin and 6,8-diprenylnaringenin) n or polyphenolic hop extracts showed progestogenic or androgenic bioactivity . These results indicate that the endocrine properties of hops and hop prod ucts are due to the very high estrogenic activity of 8-prenylnaringenin and concern must be expressed about the unrestricted use of hops in herbal pre parations for women.