Differences in the Levels of the Selected Phytoestrogens and Stable Isotopes in Organic vs. Conventional Hops and Beer

Abstract

Xanthohumol (XN), isoxanthohumol (IX) and 8-prenylnaringenin (8-PN) are important prenylflavonoids present in hops with potential beneficial properties. In this study, we examined differences in the content of XN, IX and 8-PN in hops and beer produced under organic and conventional production regimes. A An ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) method for analysing XN, IX and 8-PN in hops and beer was developed and validated, with LOQ ranging from 0.5 to 10 ng/mL. Finally, we examined 15N/14N and 12C/13C isotope ratios in the hops and beer using isotope ratio mass spectrometry (IRMS). The results show no statistically significant difference in the content of the selected prenylflavonoids between organic and conventionally produced hops and beer—in the whole sample group, as well as between the matched pairs. Stable isotope analysis indicated that only δ15N values are statistically higher in organically produced hops and beer. However, the differentiation according to the type of production could not be made solely based on the δ15N signature, but it could be used to provide supporting evidence.

The Potent Phytoestrogen 8-Prenylnaringenin: A Friend or a Foe?

“…The bulk of the methods described to date for 8-PN quantification have combined LC or HPLC separation with detection by mass spectrometry (MS), although a gas chromatography (GC)–MS method has also been published [ 15 , 19 , 20 , 26 , 27 , 28 , 29 ] ( Table 1 ). The varieties of MS used include electron impact (EI), atmospheric pressure electrospray ionization (ESI), or atmospheric pressure chemical ionization (APCI) in either positive or negative ion modes [ 15 , 18 , 24 , 30 ].…”

“…For 8-PN, these reductions can be even larger (up to 50% in a week) [ 18 ]. No differences in 8-PN, IX, or XN concentrations between organically and conventionally produced hops and beer were detected [ 19 ].…”

“…Two of the most abundant of the metabolites, (E)-8-(4’’-hydroxy isopentenyl)naringenin (8-PN-OH) and (E)-8-(4’’-oxoisopentenyl)naringenin (8-PN=O), exhibited estrogenic activity in vitro. Cytochromes P450 (CYPs), including CYP2C8 and CYP2C19, catalyzed the phase I reaction of alcohol formation in the prenyl side chain of 8-PN [ 19 ]. The alcohol derivatives of 8-PN produced in hepatocytes were subsequently conjugated to at least six glucuronides but apparently no sulfates.…”