2.4.3. ABTS [2,20-azinobis(3-ethylbenzthiazoline-6-sulphonic acid)]assay
For ABTS determination a modified method of Miller and Rice- Evans (1998) was used; 55 mg ABTS were dissolved in 2 mL 5 mM phosphate buffer (phosphate buffer pH ผ7.4 was prepared by mixture of 5 mM KH2PO4 and Na2HPO4 solutions in the ratio 1:4 v/v). ABTS was activated to ABTS_ by addition of 1 g MnO2 with stirring for 30 min, and then the solution was centrifuged for 10 min at 7000 r.p.m. The solution was filtered through a syringe filter (0.2 mM) and diluted with the phosphate buffer to absorbency 0.600_ 0.010 at t0 (t ผ0 min). A 10 mL honey sample (0.5 g mL_1) was added to 2 mL ABTS_ solution and absorbency was measured after 20 min (t20) at lผ 734 nm and AOA (%) expressed from the Eq. (1) in mg ascorbic acid equivalent in kg of honey. Average values were determined from five parallel determinations.