Total phenolics
Oils (0.5 g) were extracted with methanol (5 ml) twice, dried by gently blowing nitrogen, and resuspended in 1 ml methanol. Then, the content of total phenolics was determined following the previously reported method (Singleton & Rossi, 1965) using PerkinElmer Lambda 35 UV/Vis spectrophotometer (Perkin Elmer, Waltham, MA, USA) at 765 nm. The calibration curve was obtained with 0, 50, 100, 150, 250, 500, and 100 mg/L gallic acid solutions, which were prepared by dissolving gallic acid (0.050 g) in 1 ml ethanol, bringing to 100 ml with deionized water, and diluting with water to the desired concentrations. Total phenolics is reported as an average gallic acid equivalent (GAE, mg/g) value of four values (two experimental replicates × two analytical replicates).