Determination of anti-oxidant activity by electron spin resonance spectroscopy

A method to assess anti-oxidant activity quantitatively is presented. In th is method, free radicals (OH.) were produced from the Fenton reaction. Elec tron spin resonance spectroscopy (ESR) was then used to determine the effec tiveness of five anti-oxidants to scavenge the free radicals. Antioxidant a ctivity was assessed as the percentage reduction of the ESR signal intensit y relative to that of a control after 10 min. The order of the potency of t he antioxidants at 4.8 nM was: caffeic acid > o-coumarin > 6,7-dihydroxy-4- methylcoumarin > catechin > scopoletin. In addition, pro-oxidant activity ( a higher ESR signal intensity than that of the control) was observed for ca techin and scopoletin at low concentrations (below 3.6mM). (C) 2000 Society of Chemical Industry.