Determination of oxygen radical absorbance capacity (ORAC)
Oxygen radical absorbance capacity (ORAC) was determined according to Ou et al. (2001). Briefly, 100 L of 500 nM fluorescein and 25 L of diluted M. plumbea extracts were pipetted into each working well of a microplate (96 well) preincubated at 37 ◦C. Thereafter, 25 L of 250 mM AAPH was quickly added and the microplate was shaken for 5 s in a microtiter plate fluorometer Multiskan Ascent instrument (Labsystems, Helsinki, Finland). Thefluorescence (Ex. 485 nm, Em. 510 nm) was read every 3 min over 90 min. Net area under the curve was used to calculate antioxidant
capacity which was expressed in trolox equivalents (TE).