Chang Qi, Zuo Zhong, Chow Moses S S, Ho Walter K K
Faculty of Medicine, School of Pharmacy, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
Eur J Pharm Biopharm. 2005 Apr;59(3):549-55. doi: 10.1016/j.ejpb.2004.10.004.
The present study was to investigate oral absorption of the two similar flavonoid glycosides, isoquercitrin (IQ, quercetin-3-O-glucoside) and hyperoside (HP, quercetin-3-O-galactoside) in rats. Two groups of male SD rats received an oral dose of either IQ (4.5 mg/kg) or HP (6.0 mg/kg). Blood samples were collected via jugular vein at time intervals after drug administration and the plasma concentrations of the studied compounds were analyzed by HPLC. The stability of IQ and HP in the GI tract was also measured by incubation with various GI contents from rats. The results showed that unchanged IQ was barely detectable whereas the glucuronidated quercetin (the aglycone of IQ) was found to be the major form in plasma after oral administration of IQ. In contrast, HP could not be detected in plasma neither as unchanged form nor its aglycone or conjugated aglycone form. Additional in vitro stability studies demonstrated that HP is more stable than IQ in the GI tract. This suggests that IQ could be hydrolyzed easier than HP to its aglycone in GI tract before being absorbed. In conclusion, IQ, as a flavonoid glucoside, could be rapidly absorbed and transformed into glucuronidated quercetin and such absorption might be related to the hydrolysis of the type of sugar moieties attached to its aglycone molecule.
本研究旨在考察两种结构相似的黄酮苷，异槲皮苷（IQ，槲皮素 - 3 - O - 葡萄糖苷）和金丝桃苷（HP，槲皮素 - 3 - O - 半乳糖苷）在大鼠体内的口服吸收情况。两组雄性SD大鼠分别口服给予IQ（4.5 mg/kg）或HP（6.0 mg/kg）。给药后在不同时间间隔经颈静脉采集血样，采用高效液相色谱法分析所研究化合物的血浆浓度。还通过与大鼠的各种胃肠道内容物孵育来测定IQ和HP在胃肠道中的稳定性。结果表明，口服IQ后，几乎检测不到未变化的IQ，而葡萄糖醛酸化的槲皮素（IQ的苷元）是血浆中的主要形式。相比之下，在血浆中既未检测到未变化形式的HP，也未检测到其苷元或共轭苷元形式。额外的体外稳定性研究表明，HP在胃肠道中比IQ更稳定。这表明在吸收前，IQ在胃肠道中比HP更容易水解为其苷元。总之，作为黄酮苷的IQ能够被快速吸收并转化为葡萄糖醛酸化的槲皮素，这种吸收可能与其苷元分子上连接的糖基类型的水解有关。
