Spectroscopic and molecular modeling studies of human serum albumin interaction with propyl gallate

Propyl gallate (PG) has been used as an antioxidant in the food industry. Because of its widespread use in the food industry, the toxicology of PG should be well addressed. In this study, for the first time, we report on the interaction of PG with human serum albumin (HSA) using fluorescence and circular dichroism (CD) spectroscopy. The fluorescence spectroscopy analysis showed a significant decrease in the fluorescence intensity of HSA upon increasing the concentration of PG. Further, the fluorescence quenching was found to be resultant from the formation of the PG-HSA complex, hence the quenching mechanism was rather a dynamic procedure. The positive values of enthalpy (Delta H), and entropy (Delta S) and the negative value of the Gibb's free energy (Delta G) indicated that hydrophobic interactions play a major role in the complexation of PG with HSA. To show the impact(s) of PG on the secondary structure of HSA, we capitalized on a CD technique, which showed a significant change in the secondary structure of HSA upon complexation with PG leading to a profound reduction of the alpha-helices content of HSA. Molecular modeling analysis confirmed that the hydrophobic interaction was the major intermolecular force that stabilizes the PG-HSA complex. Based on these findings, it can be concluded that PG molecules are dynamically bound to HSA and effectively distributed within the body.