Kinetic study of the quenching reaction of singlet oxygen by flavonoids in ethanol solution
Kinetic study of the quenching reaction of singlet oxygen by flavonoids in ethanol solution
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DOI：
10.1021/jp0451389
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发表时间：
2005-03-10
影响因子：
3.3
通讯作者：
Mukai, K
中科院分区：
文献类型：
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作者：
Nagai, S;Ohara, K;Mukai, K
用分光光度法测定了7种具有2,3-双键的黄酮类化合物（黄酮、黄酮醇、菊花素、芹菜素、芦丁、槲皮素和杨梅素）在35℃乙醇中对O-1(2)的猝灭速率。总速率常数k(Q) (=k（Q) + k(r)，物理猝灭+化学反应）随着取代到黄酮类化合物骨架上的OH基团（即黄酮类化合物总给电子能力）的增加而增加。b环中邻苯二酚或邻苯三酚结构的存在是黄酮类化合物O-1(2)猝灭所必需的。发现Log k(Q)与它们的峰值氧化电位E-P相关；E-P值越小的黄酮类化合物反应活性越高。同样，黄酮类化合物的log k(Q)值与pm3mo方法计算的最高已占据分子轨道（E-HOMO）的能级和最长波长pipi*激发能（E-ex）相关。在这些类黄酮中，发现化学反应的贡献（k(r)）可以忽略不计。芦丁、槲皮素和杨梅素的k(Q)值[（1.21相似于5.12）× 10(8) M-1 s(-1)]大于脂质[（0.9相似于6.4）× 10(4) M-1 s(-1)]、氨基酸(< 3.7 × 10（7) M-1 s(-1)）和DNA (5.1 × 10(5) M-1 s(-1))]。结果表明，这些类黄酮可能通过淬灭O-1来保护食物和植物的氧化损伤(2)。
The quenching rate of singlet oxygen (O-1(2)) by seven kinds of flavonoids (flavone, flavonol, chrysin, apigenin, rutin, quercetin, and myricetin) with 2,3-double bonds has been measured spectrophotometrically in ethanol at 35 degreesC. The overall rate constants k(Q) (=k(q) + k(r), physical quenching + chemical reaction) increased as the number of OH groups substituted to the flavone skeleton (that is, the total electron-donating capacity of flavonoids) increases. The existence of catechol or pyrogallol structure in the B-ring is essential for the O-1(2) quenching of flavonoids. Log k(Q) was found to correlate with their peak oxidation potentials, E-P; the flavonoids that have smaller E-P values show higher reactivities. Similarly, log k(Q) values of flavonoids correlate with the energy level of the highest occupied molecular orbital (E-HOMO), calculated by the PM3 MO method, and the longest wavelength pipi* excitation energy (E-ex). The contribution of the chemical reaction (k(r)) was found to be negligible in these flavonoids. The k(Q) values of rutin, quercetin, and myricetin [(1.21similar to5.12) x 10(8) M-1 s(-1)] were found to be larger than those of lipids [(0.9similar to6.4) x 10(4) M-1 s(-1)], amino acids (< 3.7 x 10(7) M-1 s(-1)),and DNA (5.1 x 10(5) M-1 s(-1)). The result suggests that these flavonoids may contribute to the protection of oxidative damage in foods and plants, by quenching O-1(2).