Free Radical Scavenging Activity Correlated With Phenolic Contents In Aqueous Methanolic Extracts Of Three Algerian Cultivars Of Sorghum:, Sorghum Bicolor "L." Moench

Abstract

Phenolics have been shown to have antioxidant and free radical scavenging effects. High levels of flavonoids and tannins have been reported in certain varieties of sorghums. Antioxidant activity of aqueous methanol extracts of three Algerian pigmented sorghum seeds AS12, AS20 and I27 were examined in relation to their contents in total phenolics, total flavonoids and tannins. Total phenols content was estimated by Folin-Ciocalteu method and expressed as mg of gallic acid, flavonoids content was estimated by AlCl 3 method and expressed as mg of quercetin extract, while tannins content was estimated by vanillin-HCl essay and expressed as mg of catechin, all per 100 g sample. Flavonoids content correlated strongly (Pearson r = - 0.945 at p ≤ 0.01) with their antioxidant activity investigated by Free radical, 2,2-diphenyl-1-picrylhydrazyl (DPPH*) scavenging essay. However, total phenolics and tannin contents had less effect on (A %). The most important extraction yield (4.79±0.11%) was obtained with AS12 cultivar. AS20 showed the highest levels of total phenolics (3214.46±263.64 mg/100 g), flavonoids (32.03±1.64 mg/100 g) and tannins (615.35±6.10 mg/g) contents; however, comparable flavonoids content was recorded in I27 extract giving statically a comparable DPPH inhibition concentration (IC 50 = 39.5±2.11 µg/mL of AS20 extract compared to 72.0±2.1 µg/mL of I27 extract). The potency of radical scavenging effect of these sorghums extracts was until four times greater than synthetic antioxidant butylated hydroxytoluene (BHT). The lower radical scavenging effect was observed with AS12 where IC 50 exceeded 600 µg/mL crud extract. These results indicated that greater amount of phenolic including tannins and flavonoids compounds leads to more potent radical scavenging and showed In Salah tannin-sorghum seeds as a potential source of natural antioxidants which can replace synthetic additives.