Extraction and characterization of lipids and phenolic compounds from the brans of different wheat varieties

The lipids and phenolic compounds of wheat bran (WB) and hemicellulose B (water extractable Hemi. B and alkali extractable Hemi. B) fractions from four wheat varieties were investigated. The X-ray diffraction pattern and NMR spectra of those Hemi. B were also studied. The predominant lipid components identified in WB include triacylglycerols (41.58–53.24 wt %) and free fatty acids (7.62–13.85 wt %) with the highest content in HD-2967 and C-306 varieties (9.13 and 13.85 wt %, respectively). The WE-Hemi. B had more lipids than the AE-Hemi. B fractions. The HD-3086 variety had the highest lipid content in both its WE-Hemi. B and AE-Hemi. B fractions (6.60 and 3.19 wt %, respectively). The bound phenolic content in WB was higher (1160–2848.88 μg GAE/g) than free phenolic content (564.17–724.72 μg GAE/g). The total antioxidant activity (TAA) of WB varied from 11.76 to 13.01 μmol TE/g. The bound protocatechuic and ferulic acids were the major phenolic acids with the highest content in WB of HS-490 and HD-2967 variety, respectively. The major flavonoid identified in WB was bound catechin (70.98–198.58 μg/g) with the highest content in HD-2967. The ferulic acid was quantified as the major phenolic acid in Hemi. B fractions with a significantly higher level in WE-Hem-B (439.0–627.0 μg/g) compared to AE-Hemi. B (5.7–13.0 μg/g) fractions. The level of syringaldehyde varied from 0.8 to 1.4 μg/g in AE-Hemi. B while p-coumaric acid content in AE-Hemi. B and WE-Hemi. B varied from 0.2 to 0.3 and 5.8–9.7 μg/g, respectively. Sinapic acid and syringaldehyde were detected only in WE-Hemi. B fractions of HD-2967 and C-306 varieties. The X-ray diffractograms of WE-Hemi. B and AE-Hemi. B showed an amorphous profile with a broad peak in the region of 2θ 15–23°. The structural elucidation of Hemi. B by ¹H NMR analysis indicated the xylose backbone with substitution mainly at C(O)-3 and/or C(O)-2 positions by arabinose residues and presence of esterified ferulic acid residues attached to arabinose side chains.