Articles
PRENYLFLAVONOIDS ACCOUNT FOR INTRIGUING BIOLOGICAL ACTIVITIES OF HOPS
Article number
668_23
Pages
175 – 190
Language
English
Abstract
Hops (Humulus lupulus L.) prove to be a very rich source of prenylated hop polyphenols and derivatives, which, in addition to their essential role in flavoring beer, account for intriguing health-beneficial properties as well.
Biosynthetic pathways involve acylation and prenylation of phloroglucinol, which also serves as a precursor to hop acids including humulones (alphaacids) and lupulones (beta acids). It appears that mixed hydrophilic – hydrophobic properties of prenylated polyphenols determine biological efficacies.
Coupling of prenyl groups delivers terpenes that are main constituents of hop essential oils and contribute greatly to a hoppy aroma.
A volatile isoprenoid alcohol is held responsible for the sedative activity of hops.
Health aspects of humulones and derivatives thereof, mainly isohumulones (iso-alphaacids), as well as of lupulones, require close attention and varying interesting biological activities have been observed.
Regarding hop prenylflavonoids, most prominent prenylchalcones are xanthohumol (up to 1.3%, m/m) and desmethylxanthohumol (up to 0.2%, m/m). Prenylchalcones can be readily converted to isomeric prenylflavanones, whereby xanthohumol gives rise to isoxanthohumol and desmethylxanthohumol furnishes a mixture of 8-prenylnaringenin and 6-prenylnaringenin. 8-Prenylnaringenin has been shown to be the most potent phytoestrogen currently known, hence, desmethylxanthohumol serves as a pro-estrogen.
Xanthohumol exhibits an exceptionally broad spectrum of inhibition mechanisms at all stages of carcinogenesis, but other interesting biological activities have been observed as well.
It follows that levels of both prenylchalcones in hops determine significantly the value of a particular hop cultivar for medicinal purposes.
It should be taken into account that different hop cultivars possess varying contents of these key compounds.
Furthermore, organic hops prove to be superior for production of elevated levels of prenylchalcones and, even, for a most efficient access to desmethylxanthohumol.
Biosynthetic pathways involve acylation and prenylation of phloroglucinol, which also serves as a precursor to hop acids including humulones (alphaacids) and lupulones (beta acids). It appears that mixed hydrophilic – hydrophobic properties of prenylated polyphenols determine biological efficacies.
Coupling of prenyl groups delivers terpenes that are main constituents of hop essential oils and contribute greatly to a hoppy aroma.
A volatile isoprenoid alcohol is held responsible for the sedative activity of hops.
Health aspects of humulones and derivatives thereof, mainly isohumulones (iso-alphaacids), as well as of lupulones, require close attention and varying interesting biological activities have been observed.
Regarding hop prenylflavonoids, most prominent prenylchalcones are xanthohumol (up to 1.3%, m/m) and desmethylxanthohumol (up to 0.2%, m/m). Prenylchalcones can be readily converted to isomeric prenylflavanones, whereby xanthohumol gives rise to isoxanthohumol and desmethylxanthohumol furnishes a mixture of 8-prenylnaringenin and 6-prenylnaringenin. 8-Prenylnaringenin has been shown to be the most potent phytoestrogen currently known, hence, desmethylxanthohumol serves as a pro-estrogen.
Xanthohumol exhibits an exceptionally broad spectrum of inhibition mechanisms at all stages of carcinogenesis, but other interesting biological activities have been observed as well.
It follows that levels of both prenylchalcones in hops determine significantly the value of a particular hop cultivar for medicinal purposes.
It should be taken into account that different hop cultivars possess varying contents of these key compounds.
Furthermore, organic hops prove to be superior for production of elevated levels of prenylchalcones and, even, for a most efficient access to desmethylxanthohumol.
Publication
Authors
D. De Keukeleire, A. Heyerick
Keywords
hop acids, hop essential oil, hop polyphenols, desmethylxanthohumol, xanthohumol, 8-prenylnaringenin
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