Conjugation of vitamin C with serum proteins: A potential application for vitamin delivery

Vitamin C plays an important role in human health and therefore, the bioavailability and delivery of this micronutrient in solution have been the subject of intensive studies. Serum proteins are known to play an important role as drug delivery tools with important clinical applications. The conjugation of l-ascorbic acid with human serum albumin (HSA), bovine serum albumin (BSA) and beta-lactoglobulin (β-LG) was investigated in aqueous solution at physiological pH. Multiple spectroscopic methods, thermodynamic analysis and modeling were used to determine the binding efficacy of the vitamin C with serum proteins. Acid-protein conjugation occurred via ionic contacts. Acid forms more stable adducts with β-LG with the order of stability β-LG > HSA > BSA. The loading efficacy was 45-60%. Major alterations of protein secondary structures were observed upon acid conjugation. Serum proteins can deliver vitamin C in vitro.