Antioxidant activity of water soluble vitamins in the TEAC (trolox equivalent antioxidant capacity) and the FRAP (ferric reducing antioxidant power) assays

Thiamine (vitamin B1), folic acid (vitamin B9), pyridoxine, pyridoxal and pyridoxamine (vitamin B6) were studied for their antioxidant activity using trolox equivalent antioxidant capacity (TEAC) assay with ABTS+ radical cation and ferric reducing antioxidant power (FRAP) assay. All vitamins tested were able to scavenge ABTS+ radical cation although they reacted with it relatively slowly. The reaction could be described by pseudo-first order kinetics. The highest free radical scavenging activity was found for thiamine, followed by folic acid and vitamin B6 forms. In the FRAP assay, only folic acid showed ability to reduce Fe3+ although its activity was found to be very low. The study constitutes a starting point for more detailed study of the antioxidant activity of water-soluble vitamins and their analogues, especially in view of the use of vitamins for food fortification and as nutritional supplements.