Miranda C L, Stevens J F, Ivanov V, McCall M, Frei B, Deinzer M L, Buhler D R
Department of Environmental and Molecular Toxicology, Department of Chemistry, Linus Pauling Institute, Corvallis, Oregon, USA.
J Agric Food Chem. 2000 Sep;48(9):3876-84. doi: 10.1021/jf0002995.
Prenylated flavonoids found in hops and beer, i.e., prenylchalcones and prenylflavanones, were examined for their ability to inhibit in vitro oxidation of human low-density lipoprotein (LDL). The oxidation of LDL was assessed by the formation of conjugated dienes and thiobarbituric acid-reactive substances (TBARS) and the loss of tryptophan fluorescence. At concentrations of 5 and 25 microM, all of the prenylchalcones tested inhibited the oxidation of LDL (50 microg protein/ml) induced by 2 microM copper sulfate. The prenylflavanones showed less antioxidant activity than the prenylchalcones, both at 5 and 25 microM. At 25 microM, the nonprenylated chalcone, chalconaringenin (CN), and the nonprenylated flavanone, naringenin (NG), exerted prooxidant effects on LDL oxidation, based on TBARS formation. Xanthohumol (XN), the major prenylchalcone in hops and beer, showed high antioxidant activity in inhibiting LDL oxidation, higher than alpha-tocopherol and the isoflavone genistein but lower than the flavonol quercetin. When combined, XN and alpha-tocopherol completely inhibited copper-mediated LDL oxidation. These findings suggest that prenylchalcones and prenylflavanones found in hops and beer protect human LDL from oxidation and that prenylation antagonizes the prooxidant effects of the chalcone, CN, and the flavanone, NG.
对啤酒花和啤酒中发现的异戊烯基黄酮类化合物，即异戊烯基查耳酮和异戊烯基黄烷酮，进行了抑制人低密度脂蛋白（LDL）体外氧化能力的研究。通过共轭二烯和硫代巴比妥酸反应性物质（TBARS）的形成以及色氨酸荧光的丧失来评估LDL的氧化。在5和25微摩尔浓度下，所有测试的异戊烯基查耳酮均抑制了由2微摩尔硫酸铜诱导的LDL（50微克蛋白质/毫升）的氧化。在5和25微摩尔浓度下，异戊烯基黄烷酮的抗氧化活性均低于异戊烯基查耳酮。基于TBARS的形成，在25微摩尔浓度下，未异戊烯基化的查耳酮查耳酮柚皮素（CN）和未异戊烯基化的黄烷酮柚皮素（NG）对LDL氧化产生促氧化作用。啤酒花和啤酒中的主要异戊烯基查耳酮黄腐酚（XN）在抑制LDL氧化方面表现出高抗氧化活性，高于α-生育酚和异黄酮染料木黄酮，但低于黄酮醇槲皮素。当XN和α-生育酚联合使用时，可完全抑制铜介导的LDL氧化。这些发现表明，啤酒花和啤酒中发现的异戊烯基查耳酮和异戊烯基黄烷酮可保护人LDL免受氧化，并且异戊烯基化可拮抗查耳酮CN和黄烷酮NG的促氧化作用。
