Determination of antioxidant capacity in corn germ, wheat germ and wheat bran using solvent and Microwave-Assisted Solvent Extraction

Abstract

Solvent extraction methods are widely used for extracting antioxidant in foods and other sources. In this study, Traditional Solvent Extraction (TSE) and Microwave-Assisted Solvent Extraction (MASE) were utilized to determine the content of antioxidants in corn germ, wheat bran and wheat germ. Corn germ, wheat bran and wheat germ all contain different levels of antioxidants; TSE and MASE were utilized to determine the content of antioxidants in these three samples. TSE was performed at 60 ¨¬C employing three solvents, acetone, hexane and methanol. MASE was performed using the solvent methanol at four different temperatures, 60, 80, 100 and 120 ¨¬C. DPPH (2,2-Diphenyl-1-picrylhydrazyl) Assay was used to determine antioxidant capacity. For all samples, the most antioxidant capacity extracted using the TSE was achieved using methanol as the solvent, results ranged from 0.42-4.69 nmol Trolox/g. Using acetone and hexane as solvents for TSE yielded much lower antioxidant capacities. The MASE demonstrated consistent results compared with the TSE using methanol. In regard to wheat bran and corn germ, the capacity for antioxidants and phenolics content improved with each increase in temperature. Wheat germ yielded 3.36-3.88 nmol/g for the DPPH assay and 1248-1575 ¥ìg catechin equivalents /g for phenolics assay establishing wheat germ as containing the most antioxidant contents of the three samples. Corn germ and wheat bran displayed antioxidant capacities on a much smaller scale. The sample of corn germ¡¯s antioxidant capacity had a range of 0.90-1.19 nmol/g and 539-730 ¥ìg catechin equivalents /g, and wheat bran¡¯s antioxidant capacity and phenolics ranged from 0.39-0.72 nmol/g and 318.2-489.5 ¥ìg catechin equivalents /g. Both extraction methods were found reliable for determining the antioxidant contents of grains when methanol was employed.