Interaction of aspirin and vitamin C with bovine serum albumin

Vitamin C (L-ascorbic acid) has a major biological role as a natural antioxidant. Aspirin belongs to the nonsteroidal anti-inflammatory drugs and functions as an antioxidant via its ability to scavenge-OH radicals. Bovine serum albumin (BSA) is the major soluble protein constituent of the circulatory system and has many physiological functions including transport of a variety of compounds. In this report, the competitive binding of vitamin C and aspirin to bovine serum albumin has been studied using constant protein concentration and various drug concentrations at pH 7.2. FTIR and UV-Vis spectroscopic methods were used to analyze vitamin C and aspirin binding modes, the binding constants and the effects of drug complexation on BSA stability and conformation. Spectroscopic evidence showed that vitamin C and aspirin bind BSA via hydrophilic interactions (polypeptide and amine polar groups) with overall binding constants of K(vitamin) (C-BSA) = 1.57 x 10(4) M(-1) and K(aspirin-BSA) = 1.15 x 10(4) M(-1); assuming that there is one drug molecule per protein. The BSA secondary structure was altered with major decrease of alpha-helix from 64% (free protein) to 57% (BSA-vitamin C) and 54% (BSA-aspirin) and beta-sheet from 15% (free protein) to 6-7% upon drug complexation, inducing a partial protein destabilization. (C) 2011 Elsevier B.V. All rights reserved.