Free radical scavenging properties of conjugated linoleic acids

Conjugated linoleic acids (CLA) were investigated for free radical scavengi ng properties against the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH .) by electron spin resonance (ESR) spectrometry and spectrophotometric met hods. ESR results demonstrated that CLA directly reacted and quenched free DPPH radicals in benzene, while spectrophotometric analysis showed the radi cal scavenging capacity of CLA in ethanol. Dose and time effects of CLA-DPP H. reactions were observed in both tests. The ED50 Of CLA was 18 mg/mL unde r experimental conditions. CLA are much weaker radical scavengers as compar ed to vitamin E, vitamin C, and BHT. Kinetics of CLA-DPPH. reactions was di fferent to that of linoleic acid (LA)-DPPH. reactions. CLA reacted and quen ched DPPH. radicals at all tested levels without a lag phase, while LA had a lag phase and showed no radical quenching activity at levels of 5-80 mg/m L in 30 min. These data indicated that CLA can provide immediate protection against free radicals, but LA cannot.