Free radical-scavenging capacity, antioxidant activity, and phenolic composition of green lentil (Lens culinaris)

Phenolics were extracted from green lentil seeds with 80% (v/v) aqueous acetone, and the resultant extracts were further separated on a Sephadex® LH-20 column. Fraction I, comprising low-molecular-weight phenolics, was eluted from the column with 95% (v/v) ethanol. Fraction II, consisting predominantly of tannins, was obtained using acetone:water (1:1; v/v) as the mobile phase. Phenolic compounds present in the preparations showed antioxidant and radical-scavenging properties as revealed by a β-carotene-linoleate model system, the total antioxidant activity (TAA) method, the DPPH scavenging activity assay, and a reducing power assay. Data from these tests showed the greatest efficacies coming from the tannins (i.e., fraction II); the mean TAA of the tannin fraction was 6.09 μmol Trolox eq./mg fraction (d.w.), whereas the crude extract and fraction I showed 0.75 and 0.33 μmol Trolox eq./mg extract or fraction (d.w.), respectively. The content of total phenolics in fraction II was the highest (338 mg catechin eq./g fraction, d.w.), and the tannin content, as determined by the vanillin/HCl method and expressed as absorbance units at 500 nm per 1 g, was 252. Twenty compounds (hydroxycinnamates, procyanidins, gallates, flavonols, dihydroflavonols, dihydrochalcones) were identified in the crude extracts by HPLC-PAD and HPLC–ESI-MS techniques. Catechin and epicatechin glucosides, procyanidin dimers, quercetin diglycoside, and trans-p-coumaric acid were the dominant phenolics in green lentils.