Chiral separation of isoxanthohumol and 8‐prenylnaringenin in beer,hop pellets and hops by HPLC with chiral columns |
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Abstract: | Xanthohumol, isoxanthohumol, and 8‐prenylnaringenin in beer, hop and hop pellet samples were analyzed by HPLC using an InertSustain phenyl column and the mobile phase containing 40% methanol and 12% 2‐propanol. Fractions of isoxanthohumol and 8‐prenylnaringenin obtained by the above HPLC were separately collected. Isoxanthohumol and 8‐prenylnaringenin were enantioseparated by HPLC using a Chiralcel OD‐H column with a mobile phase composed of hexane–ethanol (90:10, v/v) and a Chiralpak AD‐RH column with a mobile phase composed of methanol–2‐propanol–water (40:20:40, v/v/v), respectively. Isoxanthohumol and 8‐prenylnaringenin from beer, hop and hop pellet samples were found to be present in a racemic mixture. This can be explained by the fact that the two analytes were produced by a nonenzymatic process. The effects of boiling conditions on the conversion of xanthohumol into isoxanthohumol were also studied. A higher concentration of ethanol in heating solvent resulted in a decrease in the conversion ratio and the conversion was stopped by addition of ethanol at >50% (v/v). The isomerization was significantly affected pH (2−10) and the boiling medium at pH 5 was minimum for the conversion. Therefore, it was suggested that xanthohumol was relatively difficult to convert to isoxanthohumol in wort (pH 5−5.5) during boiling. |
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Keywords: | 8‐prenylnaringenin beer enantioseparation hops isoxanthohumol |
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