Bioactive Compound Composition and Antioxidant Activity of Aleurone Layers and Whole Grains from Algerian Cultivars of Soft Wheat (Triticum aestivum), Durum Wheat (Triticum durum), and Barley (Hordeum vulgare)

The outer layers of wheat and barley, especially the aleurone layer (AL), are mostly removed with the bran during white flour production. This study aimed to analyze and compare AL and whole grain (WG) extracts of three cereals; soft wheat (Triticum aestivum, Arz), durum wheat (Triticum durum, Ofanto), and barley (Hordeum vulgare, Rihane) to assess their secondary metabolites, including phenolic compounds, flavonoids, and condensed tannins, as well as their antioxidant activity. The structural/morphological features of the cereal species were examined using scanning electron microscopy. The total polyphenol (TP), flavonoid, (TF) and condensed tannin (CT) contents of the WG and AL of the cereal extracts were determined using colorimetric methods. The antioxidant activity was determined using 2, 2-diphenyl-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays. Among the WG extracts, ‘Rihane’ showed the highest TPC (1.788 ± 0.012 mg GAE/g), TF (0.082 ± 0.009 mg QE/g), and CT (0.03 ± 0.01 mg CE/g). In AL extracts, TPC ranged from 0.889 ± 0.012 to 1.397 ± 0.060 mg GAE/g, and TFC from 0.022 ± 0.01 to 0.030 ± 0.01 mg QE/g, with AL ‘Ofanto’ showing slightly higher values. The highest tannin content in both WG and AL was recorded for ‘Rihane’ with tannin content of 0.054 ± 0.006 mg CE/g (WG) and 0.043 ± 0.01 mg CE/g (AL). WG ‘Rihane’ had the most potent antioxidant activity (DPPH IC50 = 752 µg/mL). These findings highlight the nutritional potential of the aleurone layer as a valuable source of bioactive compounds including antioxidants.