Modelling of reaction between antioxidants and free radicals

Abstract

Radical scavenging ability (RSA) of the polyphenols was determined experimentally by kinetic parameters (rate constants, k and activation energy Ea) in different solvents using the stopped-flow technique and computationally by the molecular parameter, OH bond dissociation enthalpy (OH BDE) using density functional theory/ B3LYP method in Gaussian 98. Kinetic study on the model phenolic compounds reveals that rate of radical scavenging reaction of polyphenols depend not only the number and position of OHs but also the presence of electron donating groups (EDGs) in the structure. Computational study reveals that the presence of intramolecular hydrogen bond (IHB), which decreases the OH BDEs of phenols. Epigallocatechin gallate (EGCG), a tea polyphenol, showed the greater RSA (Ea = 60.9 kJ mol-1 against DPPH radical).