Influence of cyclodextrins on the kinetics of oxidation of amino acids and BSA by hydrazyl radicals

The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied. The rate decreases in the order Arg > Lys > Tyr > Thr > His similar to BSA similar to Phe similar to Gly-His with both free radicals. Addition to the reaction mixture of alpha- and beta -cyclodextrin decreases the oxidation rate, probably due to amino acid encapsulation in the cyclodextrin cavity. beta -Cyclodextrin protects more efficiently against oxidation than alpha -cyclodextrin.