SCREENING OF ANTIOXIDATIVE ACTIVITY OF SPICES - A COMPARISON BETWEEN ASSAYS BASED ON ESR SPIN-TRAPPING AND ELECTROCHEMICAL MEASUREMENT OF OXYGEN-CONSUMPTION

Spices belonging to the Labiatae family were used to develop assays fo r evaluation of antioxidative activity of spices and spice extracts. T wo different principles for detection of antioxidative activity were u sed: (i) an ESR spin trapping technique in which hydroxyl radicals wer e generated by the Fenton reaction and trapped by 5,5-dimethyl-1-pyrro line-N-oxide (DMPO) in competition with spice extract constituents, (i i) electrochemical measurement of oxygen depletion rate in a heterogen eous lipid/water emulsion with lipid oxidation initiated by metmyoglob in. The ESR free radical method relates to the effect of antioxidant o n the initiation of oxidation, while the oxygen depletion method relat es to the effect of antioxidant on the propagation of oxidation. For b oth methods, marjoram and basil showed the lowest activity, while wint er savory showed the highest activity as measured by the ESR method, a nd Turkish oregano and Chilean oregano showed the highest activity as measured by the oxygen depletion method. Total phenol content in the e xtract correlates linearly with the antioxidant activity as measured b y oxygen depletion, but not with the free radical scavenging effect. I t is concluded that extracts of the investigated spices contain compon ents with at least two different antioxidative mechanisms. Copyright ( C) 1996 Elsevier Science Ltd