Vitamin C stabilized in lysozyme and CTAB aqueous solutions

Abstract

Vitamin C (VC) is an antioxidant and assists in treating cancer, but it hydrolyses and degrades in aqueous solutions due to oxidation and loses drug efficiency. It is critical to improve the stability of VC. Lysozyme (LYS) is a global protein and an enzyme, which is used as a model protein to probe the interactions of VC and protein relevant to VC degradation. Micellar solutions, formed by cationic surfactant cetyltrimethylammonium bromide (CTAB) and water, act as micro-reactors to stabilize VC. UV–vis and fluorescence spectroscopic methods are applied to investigate the interactions that control the properties of the VC-LYS-CTAB ternary model system, including kinetics of VC degradation and conformation changes of LYS (unfolding and recovery). The results suggest that LYS stabilizes VC by forming a complex and LYS partially unfolds, and CTAB micelles can slow down the rate of VC degradation. VC is the most stable in the VC- LYS-CTAB ternary system among VC-LYS, VC-CTAB aqueous solutions, and pure water. The strength of interactions decreases in the order of: VC degradation, interaction of CTAB micelles and VC, interaction of LYS and VC, and the weak hydrophobic interaction between CTAB and LYS. The former two are the major factors that control the alleviation of VC degradation and the recovery of LYS conformation. This work provides fundamental insights for drug stability and delivery, and personal product field where vitamins, proteins and surfactants are used.