Intestinal absorption and metabolism of antioxidants from plants and their suppressive effects against oxidative stress

使用大鼠外翻小肠的吸收分析表明，毛地黄黄酮在通过肠粘膜的过程中转化为葡萄糖醛酸苷，毛地黄黄酮7-o-b-葡萄糖苷在水解为毛地黄黄酮后被吸收。给药后大鼠血浆中存在游离毛地黄黄酮、其结合物和甲基化结合物。这表明一些毛地黄黄酮可以逃脱肠结合和肝硫酸化/甲基化。LC/MS分析表明，在血液中循环的主要结合物是未改变的糖苷配基的单葡糖苷酸。毛地黄黄酮及其结合物的血浆浓度分别在给药后15 min和30 min达到最高水平。木犀草素及其偶联物在大鼠体内的排泄回收率约为4%。为了评价吸附的木犀草素在人体血清中的抗氧化作用，测定了2，2-偶氮二（2-氨基丙烷）-盐酸盐（AAPH）处理的血清中TBARS和维生素C的含量。口服毛地黄黄酮后获得的血清表现出对脂质过氧化和维生素C降解的保护作用。另一方面，当小鼠暴露于多柔比星时，预先给予木犀草素和α G-芸香苷降低外周血中MNRET的频率并抑制骨髓中维生素C的降解。这些结果表明，吸收的黄酮类化合物显示抗氧化活性的协同方式与抗坏血酸。

The absorption analysis using rat everted small intestine demonstrated that luteolin was converted to glucuronides during passing through the intestinal mucosa and that luteolin 7-ο-b-glucoside was absorbed after hydrolysis to luteolin. Free luteolin, its conjugates and methylated conjugates were present in rat plasma after dosing. This suggests that some luteolin can escape the intestinal conjugation and the hepatic sulfation/ methylation. LC/MS analysis showed that the main conjugate which circulates in the blood was a monoglucuronide of the unchanged aglycone. The plasma concentration of luteolin and its conjugates reached the highest level 15 min and 30 min after dosing with luteolin in propyleneglycol, respectively. The excretory recovery of luteolin and its conjugates in rats was about 4%. Luteolin and its conjugates were also detected in human serum, and the highest peak was observed 2-3h after oral administration.In order to evaluate the antioxidant effect of absorbed luteolin in human serum, TBARS and the content of vitamin C in the serum treated with 2,2 azobis(2 aminopropane)-dihydrochloride(AAPH) were determined. The serum obtained after oral administration of luteolin showed a protective effect against lipid peroxidation and vitamin C degradation. on the other hand, preadministration of luteolin and aG-rutin reduced the frequency of MNRETs in peripheral blood and suppressed vitamin C degradation in bone marrow when mice were exposed to doxorubicin. These results suggest that absorbed flavonoids show antioxidant activity in the coordinate manner with ascorbic acid.