Calorimetric adaptation of the inhibited autoxidation method to determine the activity of individual antioxidants and natural extracts

Abstract This work aims to determine the antioxidants activity of individual and natural extracts by isothermal calorimetry. The proposed method is an adaptation “ inhibited autoxidation ”. It consists monitoring heat-flow signal evolved during styrene, in presence 2,2?-azobis(isobutyronitrile) as radical initiator, with or plant inhibitors, under conditions (303 K). resulting calorimetric traces were transformed conversion fractions over time. antioxidant was expressed initial slope period styrene autoxidation. Also, induction observed at onset uninhibited leaded stoichiometry number reaction between free radicals. approach very simple, it allowed rank ( ? -tocopherol > gallic acid = quercetin syringic synaptic 4-hydroxybenzoic acid) Olea europea Melissa officinalis Fraxinus excelsior Papaver rhoeas ), based on their ability decrease rate results critically compared those from DPPH assay. Differently many assays widely used nowadays, has merit test micromolar quantities inhibit a large excess oxidizable substrate, whose oxidation induced constant radicals formation well controlled reproducible experimental conditions.