Abstract: The absorption characteristics of the Bletilla striata extract,including blestroside (B12),α-Isobutylmalic acid (B6),gymnosides V (B17),militarine (B14),dihydrophenanthrenes 1 (B19) and gymnosides IX (B23) in rats small intestine were investigated.Study on absorption characteristics of different components in different concentrations and different intestinal segments by isolated everted intestine model.A UPLC-MS/MS method was established to determine the contents of each component and to calculate the accumulative absorption and absorption rate constants.The results showed that except for the low concentration of B6,all the components showed linear absorption at different concentrations and different intestinal segments.The regression correlation coefficient (R) was above 0.9,which was consistent with the first order absorption rate,and the absorption rate constant increased with the increase of concentration.It is suggested that the absorption mechanism of each component is passive absorption.At the same concentration,the total absorption of different intestinal segments was greater than that of ileum,colon and jejunum.In conclusion,the six components of Bletilla striata extract were absorbed in the small intestine,but the absorption of each component was selective in the small intestine.This study can provide some experimental references for the clinical development of Bletilla striata extract and the determination of drug dosage form.

Key words: Bletilla striata extract, isolated everted gut model, absorption, absorption rate constants