Search resultsActivation of proestrogens from hops (Humulus lupulus L.) by intestinal microbiota; conversion of isoxanthohumol into 8-prenylnaringenin
Title
Activation of proestrogens from hops (Humulus lupulus L.) by intestinal microbiota; conversion of isoxanthohumol into 8-prenylnaringenin
Publication type
Journal Article
Year of Publication
2005
Authors
Journal
Journal of Agricultural and Food Chemistry
Volume
53
Issue
16
Pagination
6281 - 6288
Date published
2005
ISBN
00218561 (ISSN)
Keywords
8 prenylnaringenin, 8-Prenylnaringenin, Adult, article, Bacteria, bacterium, beer, chemistry, Eubacterium, Eubacterium limosum, Feces, Fermentation, flavanone derivative, Flavanones, flavonoid, Flavonoids, hop, human, Humans, Humulus, Humulus lupulus, Intestine, Intestines, isoxanthohumol, metabolism, microbiology, O-demethylation, phytoestrogen, Phytoestrogens, Prenylflavonoids, propiophenone derivative, Propiophenones, xanthohumol
Abstract
Hop, an essential ingredient in most beers, contains a number of prenylflavonoids, among which 8-prenylnaringenin (8-PN) would be the most potent phytoestrogen currently known. Although a number of health effects are attributed to these compounds, only a few reports are available about the bioavailability of prenylflavonoids and the transformation potency of the intestinal microbial community. To test these transformations, four fecal samples were incubated with xanthohumol, isoxanthohumol (IX), and 8-PN. Upon incubation with IX, present in strong ales up to 4 mg/L, 36% was converted into 8-PN in one fecal sample and the estrogenic properties of the sample drastically increased. In an experiment with 12 fecal cultures, this conversion was observed in one-third of the samples, indicating the importance of interindividual variability in the intestinal microbial community. Eubacterium limosum was identified to be capable of this conversion (O-demethylation) of IX into 8-PN, and after strain selection, a conversion efficiency of 90% was achieved. Finally, strain supplementation to a nonconverting fecal sample led to rapid and high 8-PN production at only 1% (v/v) addition. Up to now, the concentration of 8-PN in beer was considered too low to affect human health. However, these results show that the activity of the intestinal microbial community could more than 10-fold increase the exposure concentration. Because prenylflavonoids are present in many beers with IX being the major constituent, the results raise the question whether moderate beer consumption might contribute to increased in vivo levels of 8-PN and even influence human health.