Enhancing effect of Labrafac Lipophile WL 1349 on oral bioavailability of hydroxysafflor yellow A in rats

The objective of the present investigation was to clarify the mechanism by which Labrafac Lipophile WL 1349 (WL 1349) enhanced the oral bioavailability (BA) of hydroxysafflor yellow A (HSYA), the representative low permeable hydrophilic (biopharmaceutic classification system (BCS) Class III) drug. HSYA–phospholipid complex was prepared, and dissolved into WL 1349 with a certain surfactant to form a stable oil solution. Oral administration of HSYA aqueous solution at a dosage of 4.5 mg/kg resulted a low plasma HSYA concentration with Cmax and AUC0–8 h values of 0.105 μg/ml and 10.29 μg min/ml, respectively. HSYA–phospholipid complex oil solution with the same administration and dosage increased the plasma HSYA concentration significantly with Cmax and AUC0–8 h values of 2.063 μg/ml and 381.145 μg min/ml, respectively. The results showed that WL 1349 could improve oral absorption of HSYA remarkably. Bioavailability investigations were performed to show WL 1349 dosage independent from HSYA absorption within the dosage from 1 ml/kg to 9 ml/kg. The test of bile duct ligation in rats showed that the oil solution containing WL 1349 did not result in detectable plasma HSYA concentration, but HSYA aqueous solution had the same AUC0–8 h as the bile duct was not ligated. The in vitro lipolysis experiments of WL 1349 showed that WL 1349 was emulsified by deoxycholate, and then was hydrolyzed to fatty acids and monoglycerides by pancreatic lipase rapidly. The lipolysis products of WL 1349, caprylic acid, capric acid and caprylic and capric acid monoglycerides all improved the BA of HSYA in vivo. The results above indicated the emulsifying by bile, and hydrolysis to fatty acids and monoglycerides by pancreatic lipase was one of the enhancing mechanisms of HSYA–phospholipid complex oil solution absorption.