R-PE, phosphate buffer, and samples
were preincubated at 37 ◦C for 15 min. The reaction was started by
the addition of AAPH. Fluorescence emission at 568 nm was measured and recorded every 5 min using an excitation wavelength of
541 nm using a QM-2003 PTI-Photon Technology Intl. spectrofluorometer. The experiment was ended when the sample fluorescence
was less than 5% of the initial intensity (approximately after 35 min).
For each experiment, 1 blank sample, 1 standard sample, and a maximum of 10 unknown samples were analyzed at the same time. Each
sample was analyzed in triplicate. The ORAC value refers to the net
protection area under the quenching curve of R-PE in the presence
of an oxidant. The results (ORAC values) were calculated and expressed as Trolox equivalents (TE) per gram on a fresh weight basis