Hydroxyl radical-scavenging activity assay. The hy- droxyl radical scavenging activity was determined according to the method described by Liu, Wang, Xu, and Wang (2007) with slight modifications. Briefly, 1 mL of the OLE (OFE/BPOL/ BPOF) solutions with different concentrations (0.2–1.2 mg/ mL) was added to 2 mL of sodium phosphate buffer (150 mM, pH 7.4) containing 10 mM FeSO4, 2 mM sodium salicylate and 6 mM H2O2. The mixture was incubated at 37 °C for 10 min, and the absorbance of the solution was measured at 510 nm. The hydroxyl radical-scavenging activity was calculated using the equation 100 × (A0 − A1 + A2)/A0, where A0, A1 and A2 are the ab- sorbances of the control, samples, and samples without sodium salicylate, respectively. Vc and BHT were used as positive controls.