Development of preparative and analytical methods of the hop bitter acid oxide fraction and chemical properties of its components

Abstract

The bitter acids in hops (Humulus lupulus L.) and beer, such as α-, β-, and iso-α-acids, are known to affect beer quality and display various physiological effects. However, these compounds readily oxidize, and the effect of the oxides on the properties of beer or their potential health benefits are not well understood. In this study, we developed a simple preparative method for the bitter acid oxide fraction derived from hops and designated the constituents as matured hop bitter acids (MHBA). HPLC-PDA-ESI/HRMS and MS(2) revealed that MHBA are primarily composed of α-acid-derived oxides, which possess a common β-tricarbonyl moiety in their structures similar to α-, β-, and iso-α-acids. We also developed a quantitative analytical method of whole MHBA by HPLC, which showed high precision and reproducibility. Using our newly developed method, the concentration of whole MHBA in several commercial beers was evaluated. Our results will promote the study of bitter acid oxides.

Genetic, acute and subchronic toxicity studies of matured hop extract produced by extraction from heat-treated hops

“…Finally, MHE was yielded as brown powder (approximately 7.6 kg). HPLC analysis confirmed that the MHE contained 20.5% of MHBA, as previously described (Taniguchi et al, 2015).…”

“…In contrast, oxidation of α-and β-acids produces bitter acid oxides, such as matured hop bitter acids (MHBA). All of the structurally elucidated compounds of MHBA possess a common β-tricarbonyl moiety similar to α-, β-, and isoα-acids (Taniguchi et al, 2013(Taniguchi et al, , 2014a(Taniguchi et al, , 2014b(Taniguchi et al, , 2015. We demonstrated that MHBA suppresses diet-induced body fat accumulation in animals (Morimoto-Kobayashi et al, 2015).…”

Improving Effects of Hop-Derived Bitter Acids in Beer on Cognitive Functions: A New Strategy for Vagus Nerve Stimulation

“…Representative IAA compounds include isocohumulone, isohumulone, and isoadhumulone, depending on the particular acyl side chain structure present, and each compound has cis and trans isomers ( Figure 1). Taniguchi et al [16] further determined the concentration of IAAs in commercially available beers and found 16-27 mg/L of IAAs in lager-type Japanese beer and 41-64 mg/L of IAAs in India Pale Ale, which is brewed with a large amount of hops.…”

“…According to the allometric scaling to human dose, 0.2-2 mg/kg of IAAs is equivalent to 0.03-0.3 mg/kg (2-20 mg in 70-kg person) in humans. Taniguchi et al [16] reported that 16-27 mg/L of IAAs are contained in regular types of beer, and thus effective dose of IAAs would be found in 0.13-1.3 L of beer.…”

“…These authors developed an analytical and preparative method using high performance liquid chromatography (HPLC) for α-acids, β-acids, and their oxidation products, such as humulinones and hulupones, and described structural changes during the hop oxidation process. Taniguchi et al [16] further developed a preparative method to fractionate total bitter acid oxides, and designated the oxidized fraction as matured hop bitter acids (MHBAs). They analyzed MHBA components and found that MHBAs are primarily composed of the β-tricarbonyl moiety chemical structure common in IAAs and αand β-acids ( Figure 2).…”