论文部分内容阅读
Aim:To investigate the limiting factors for oral bioavailability of flavonoids derived from the Chinese herbal remedy Xiaochaihu-tang. The investi-gational flavonoids included baicalin, wogonoside, oroxylin-A 7-O-β-D-glucopyranosiduronide, liquiritin, liquiritin apioside, isoliquiritin, and isoliquiri-tin apioside, as well as their aglycones baicalein, wogonin, oroxylin-A, liquir-itigenin, and isoliquiritigenin. Methods: Caco-2 cell monolayers were used and the apparent permeability both in apical to basolateral and basolateral to apical directions was measured for each investigational compound. Meanwhile, chemoinformatics was carried out to provide insight into the mechanism gove-ing the permeability. In addition, carrier-mediated transport with or without in-hibitors, as well as the metabolism by conjugation, was also examined with Ca-co-2 cell monolayers for the flavonoids. Results: The investigational flavonoid aglycones exhibited favorable membrane permeability, but efficient glucuronida-tion and/or sulfation by the enterocytes may limit their bioavailability. For the flavonoid glycosides, their poor membrane permeability was found to be caused by high hydrogen-bonding potential. Among the glycosides, oroxylin-A 7-O-β-D-glucopyranosiduronide, isoliquiritin, and isoliquiritin apioside were transport-ed under the mediation of the efflux transporters multidrug resistance-associated protein and/or P-glycoprotein. Conclusion: The limiting factors of oral bioavail-ability for the flavonoids derived from Xiaochaihu-tang appeared to include poor membrane permeability, significant effiux, and efficient intestinal metabolism by conjugation.