The Enhancement Effects of Forsythoside E on Serum Albumin Fluorescence Under Simulated Physiological Conditions

Abstract

This study examines the fluorescence enhancement effects of forsythoside E, one of metabolites of Forsythia suspensa, on human serum albumin (HSA) and bovine serum albumin (BSA) under simulated physiological conditions. The increase in protein fluorescence induced by forsythoside E are approximately the same in slightly acidic and neutral solutions, whereas the protein fluorescence intensities barely change in the alkaline solution after adding forsythoside E. The fluorescence increase of proteins caused by forsythoside E are significantly bigger in ethanol than in the other two solvents. The enhancement effects of forsythoside E on protein fluorescence were weakened when Cu2+ and Fe3+ were pre-added to the solution. Forsythoside E had little effect on the fluorescence of glycosylated BSA (gBSA) but increased the fluorescence of glycosylated HSA (gHSA) in a concentration-dependent manner because BSA was significantly more glycosylated than HSA. These findings can help us to understand the delivering efficiency, absorption, toxicity, and the metabolic process of forsythoside E in vivo.