Kayano Shin-Ichi, Yamada Naoko Fukutsuka, Suzuki Tomoo, Ikami Takao, Shioaki Kochiro, Kikuzaki Hiroe, Mitani Takahiko, Nakatani Nobuji
Research and Development Institute, MIKI Corporation, 12-4, Naruohama 3, Nishinomiya 663-8142, Japan.
J Agric Food Chem. 2003 Feb 26;51(5):1480-5. doi: 10.1021/jf025929c.
Prunes are known to show high antioxidant activity on the basis of the oxygen radical absorbance capacity (ORAC), and their major antioxidant components are caffeoylquinic acid isomers. The aim of this study is to prove the contribution of caffeoylquinic acid isomers to the ORAC of prunes, and to investigate the existence of other antioxidant components. Caffeoylquinic acid isomers in ethanol (EtOH) extracts of prunes were quantified by HPLC analysis, and the degree of contribution of these isomers to the ORAC was found to be 28.4%; hence, it was speculated that the remaining ORAC is dependent on other antioxidant compounds. EtOH extract was partitioned between hexane and H(2)O. The H(2)O layer was further separated into H(2)O and 2-100% methanol (MeOH) eluates by Diaion HP-20 column chromatography. Both the H(2)O and 50% MeOH eluates showed high values of total phenolics and ORAC, although the contribution of caffeoylquinic acid isomers to the ORAC was low. Therefore, it was predicted that unknown antioxidants exist in these fractions, and several compounds were identified by HPLC analysis. Furthermore, hydrolysis of EtOH extract residue led to higher levels of total phenolics and ORAC, and these results suggested the existence of conjugated antioxidant components in prunes.
基于氧自由基吸收能力（ORAC），李子具有较高的抗氧化活性，其主要抗氧化成分是咖啡酰奎尼酸异构体。本研究的目的是证明咖啡酰奎尼酸异构体对李子ORAC的贡献，并研究其他抗氧化成分的存在情况。通过高效液相色谱（HPLC）分析对李子乙醇（EtOH）提取物中的咖啡酰奎尼酸异构体进行定量，发现这些异构体对ORAC的贡献程度为28.4%；因此，推测其余的ORAC依赖于其他抗氧化化合物。将EtOH提取物在己烷和水之间进行分配。水层通过Diaion HP - 20柱色谱进一步分离为水和2 - 100%甲醇（MeOH）洗脱液。水和50% MeOH洗脱液的总酚含量和ORAC值均较高，尽管咖啡酰奎尼酸异构体对ORAC的贡献较低。因此，预计这些馏分中存在未知的抗氧化剂，并通过HPLC分析鉴定了几种化合物。此外，EtOH提取物残渣的水解导致总酚含量和ORAC水平升高，这些结果表明李子中存在共轭抗氧化成分。
