Abstract:Hop is a kind of very important traditional Chinese medicine as well as an important composition in beer brewing. The mainly source of bitterness to hops was the groups of bitter acids including alpha-acids and beta-acids, which had been studied by many researchers for their unique values recently. This paper summarized the chemical constituents, determination methods, pharmacological action and clinical applications of alpha-acids and beta-acids. It is very useful to be a reference for further research.
Key words:Humunus lupulus L.; α-acids; β-acids; Chemical constituents; Pharmacological action
2.1 高效液相色谱(HPLC)近年来,HPLC法以其样品预处理简单、快速、定量准确、灵敏度高等优点,已经成为最常用的测定啤酒中α-酸及β-酸的方法,为评价和控制啤酒花及其制品质量提供有效的分析手段。陈家华等[14]采用反向高效液相法测定酒花和酒花浸膏中的α-酸含量,以V(甲醇):V(水):V(磷酸)= 80∶20∶0.25为流动相,在 314 nm下测得酒花和酒花浸膏中的α-酸相对偏差分别为 2.02% 和 1.78%。刘玉梅等[15]也建立了啤酒花中β-酸的高效液相测定法。据报道[5],反相液相色谱法可以同时测定了啤酒花浸膏中α-酸及β-酸含量,以NovapakC18 (150 mm ×3.9 mm ID,5 μm) 为分析柱,甲醇:水(85:15,v/v,磷酸调 pH=2.5)为流动相,紫外光313nm检测。样品用甲醇溶解过滤后直接进样,外标法定量。经考察,该方法平均加样回收率高,精密度好,可以在 7min 完成一次分析,具有简单、快速、准确等特点。林艳等[16]也采用HPLC法用于啤酒工业中酒花及其制品质量评定当中。采用NncleosilC18在二极管阵列检测器,以甲醇:重蒸水:磷酸=85∶19∶0.26(体积比)作流动相,以保留时间、标样添加和特征光谱法定性,采用单点校正因子外标进行定量。
2.2 紫外分光光度法紫外分光光度法是国际贸易普遍采用的测定α-酸含量的仲裁方法[17]。有报道显示[18],采用紫外分光光度法可以缩短测定时间,减少α-酸的损失。《啤酒工业手册》(中)[19]也对ASBC(American Society of Brewing Chemistry)分光光度法测定酒花中的α-酸和β-酸作了详细描述,该方法是用碱性有机溶剂萃取酒花的α-酸和β-酸,然后在紫外光区 275,325,355 nm 测定吸光度,根据α-酸、β-酸在该三波长的吸光度,用联立方程式解出α-酸和β-酸的含量。这种比色的方法操作比较简单,是现在啤酒厂多采用的方法。李崎等[20]采用此法对10种酒花样品进行α-酸和β-酸含量的测定,并考察了不同的吸光度范围对α-酸测定结果准确性的影响。分光光度法测定啤酒花中的α-酸和β-酸虽然快速、简便,但由于每种酒花酸都包含了好几种同系的结构类似物,而每一种结构类似物在某一特定波长下的消光系数是有差异的,当它们所占比例不同时,会使总的酒花酸的消光系数发生偏移,带来测定误差。
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