Effect of honey on oxidation, chlorination and nitration by purified equine myeloperoxidase

Objective: To evaluate the antioxidant effect of honey using two classical methods generally used, and for the first time to test the effect of honey on the oxidation, chlorination and nitration by purified equine myeloperoxidase (MPO).Methods: The antioxidant activity of three Algerian honey samples (nectar honey, mixed honey and honeydew honey) was evaluated by two classical methods, the ferric-reducing/antioxidant power (FRAP) assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging capacity.Results: Honeydew honey had the highest reducing power and DPPH radical-scavenging activity, whereas nectar honey showed the lowest reducing power and DPPH radical-scavenging activity.All honey samples showed a significant inhibitory effect on the chlorination activity of equine MPO, but honeydew honey was the weakest inhibitor.The three samples were poorly inhibitor on the MPO oxidation and nitration activities, except for nectar honey that exerted an inhibitory effect at the highest tested concentration of 10%.These later results seem to contradict those obtained with DPPH and FRAP. Conclusions:The antioxidant capacity of honey is mainly due to the phenolic compounds and flavonoids it contained.It has been suggested that MPO might be involved in the antioxidant, not pro-oxidant, activity of phenolic compounds.