Chemical Characterization of Beer Aging Products Derived from Hard Resin Components in Hops (Humulus lupulus L.)

Abstract

The bitter taste of beer originates from resins in hops (Humulus lupulus L.), which are classified into two subtypes (soft and hard). Whereas the nature and reactivity of soft-resin-derived compounds, such as α-, β-, and iso-α-acids, are well studied, there is only a little information on the compounds in hard resin. For this work, hard resin was prepared from stored hops and investigated for its compositional changes in an experimental model of beer aging. The hard resin contained a series of α-acid oxides. Among them, 4'-hydroxyallohumulinones were unstable under beer storage conditions, and their transformation induced primary compositional changes of the hard resin during beer aging. The chemical structures of the products, including novel polycyclic compounds scorpiohumulinols A and B and dicyclohumulinols A and B, were determined by HRMS and NMR analyses. These compounds were proposed to be produced via proton-catalyzed cyclization reactions of 4'-hydroxyallohumulinones. Furthermore, they were more stable than their precursor 4'-hydroxyallohumulinones during prolonged storage periods.

Matured Hop Bitter Acids in Beer Improve Lipopolysaccharide-Induced Depression-Like Behavior

“…Matured hop bitter acids constitute both α- and β-acid oxidants with β-tricarbonyl structures (Taniguchi et al, 2015a,b). Effects of three major constituents (HAH, HAIH, and TCOIHA) of MHBAs on depression-like behavior were examined in TST.…”

“…Matured hop bitter acids and each of its major components [4′-hydroxyallohumulinones (HAH); 4′-hydroxyalloisohumulones (HAIH); tricyclooxyisohumulones A (TCOIH-A); hulupones; and humulinones] were prepared from hop pellets as described elsewhere (Taniguchi et al, 2015a,b). NE was purchased from Sigma-Aldrich Co. (St. Louis, MO, United States) for the analysis of monoamines.…”

Matured Hop-Derived Bitter Components in Beer Improve Hippocampus-Dependent Memory Through Activation of the Vagus Nerve

“…MHBA are a mixture of α- and β-acid oxides with β-tricarbonyl structures 17 – 19 . Five compounds (4′-hydroxyallohumulinone, HAH; 4′-hydroxy- cis -alloisohumulone, HAIH; tricyclooxyisohumulone A, TCOIH-A; cohulupone; and humulinone) found in MHBA were obtained, and the effect of each compound was examined in the Y-maze test using amnesia model mice.…”

“…MHBA and each representative component (4′-hydroxyallohumulinone, HAH; 4′-hydroxy- cis -alloisohumulone, HAIH; tricyclooxyisohumulone A, TCOIH-A; cohulupone; and humulinone) were prepared from hop pellets or synthesized as described previously 17 – 19 , 51 . 4′-Hydroxy- cis -alloisohumulone (HAIH) was purified from MHBA as described in the supplementary information.…”

“…The α- and β-acids are also converted to oxidized components called matured hop bitter acids (MHBA) that contain a β-tricarbonyl formula and a common chemical structure with iso-α-acids 17 – 19 . Because of their structural similarity to iso-α-acids, MHBA are expected to have similar physiological effects as those of iso-α-acids, such as preventing obesity and cognitive impairment.…”