Liang Ran, Han Rui-Min, Fu Li-Min, Ai Xi-Cheng, Zhang Jian-Ping, Skibsted Leif H
Department of Chemistry, Renmin University of China, Beijing 100872, China.
J Agric Food Chem. 2009 Aug 12;57(15):7118-24. doi: 10.1021/jf9013263.
The lipophilic flavonoid glycoside baicalin from the traditional oriental herb Scutellaria baicalensis Georgi (logP = 1.27, pK(a1) = 7.6, pK(a2) = 10.1 as determined at 25 degrees C in 0.1 M NaCl) is found to be as reducing (0.39 V vs NHE, reversible two-electron oxidation by CV at pH 7.4) as other catechol flavonoids but a poor radical scavenger (TEAC = 1.12, pH 7.4) and a poor antioxidant against free radical initiated lipid oxidation in liposomes. However, this compound is able to regenerate beta-carotene (beta-Car) from beta-Car(*+) with a second-order rate constant of (5.6 +/- 0.5) x 10(9) L mol(-1) s(-1) in the methanol/chloroform binary solvent (1:9, v/v) and, more importantly, to exhibit a prominent synergistic effect with beta-Car against the lipoxidation induced by AMVN-derived peroxyl radical in liposomal membrane. Thus, baicalin by itself is not an effective antioxidant, but it becomes one via interaction with beta-Car. The radical scavenging and antilipoxidation properties of baicalin are discussed in terms of its physicochemical properties and molecular structures.
传统东方草药黄芩（Scutellaria baicalensis Georgi）中的亲脂性黄酮苷黄芩苷（25℃下于0.1M NaCl中测定，logP = 1.27，pK(a1) = 7.6，pK(a2) = 10.1）被发现与其他儿茶酚类黄酮一样具有还原性（pH 7.4时，相对于标准氢电极的还原电位为0.39V，循环伏安法显示为可逆双电子氧化），但自由基清除能力较差（pH 7.4时，TEAC = 1.12），且对脂质体中自由基引发的脂质氧化的抗氧化能力也较差。然而，该化合物能够在甲醇/氯仿二元溶剂（1:9，v/v）中以(5.6 +/- 0.5) x 10(9) L mol(-1) s(-1)的二级速率常数从β-胡萝卜素阳离子（β-Car(+)）再生β-胡萝卜素（β-Car），更重要的是，它与β-Car对脂质体膜中由AMVN衍生的过氧自由基诱导的脂质氧化表现出显著的协同作用。因此，黄芩苷本身不是一种有效的抗氧化剂，但通过与β-Car相互作用可成为一种有效的抗氧化剂。本文根据黄芩苷的物理化学性质和分子结构对其自由基清除和抗脂质氧化性能进行了讨论。
