Esterification Enhanced Intestinal Absorption of Ginsenoside Rh2 in Caco-2 Cells without Impacts on Its Protective Effects against H2O2-Induced Cell Injury in Human Umbilical Vein Endothelial Cells (HUVECs)

Ginsenoside Rh2 and its octyl ester derivative (Rh2-O) were investigated for their transcellular transport in the Caco-2 cell system and their protective effect against oxidative stress in human umbilical vein endothelial cells (HUVECs). Results showed that the transport rates for apical-to-basolateral (AP-BL) flux of Rh2 (0.21 × 10–6 cm/s) was enhanced by the synthesis of its esterified derivative Rh2-O (1.93 × 10–6 cm/s) over the concentrations of 10–50 μM. In addition, both Rh2 and its esterified derivative Rh2-O exhibited similar protective effects against oxidative damage induced by H2O2. Pretreatment of Rh2 and Rh2-O significantly decreased the activation of caspase-3 known to play a key role in H2O2-induced cell apoptosis. These results were consistent with that of a flow cytometry assay analyzing HUVECs apoptosis. The present study demonstrated that the absorption of ginsenoside Rh2 in vitro can be significantly enhanced by synthesis of its ester derivative. Meanwhile, no significant discrepancy between Rh2 and Rh2-O on their bioactivities against the oxidative damage induced by H2O2 was observed, which means that esterification of Rh2 might have a higher bioavailability than Rh2 in vitro without impacts on pharmaceutical actions.