Effect of solvents extraction on phenolic content and antioxidant activity of the byproduct of eggplant

Eggplant is one of most common vegetables consumed all around the world. This study has assayed antioxidants from the byproduct (peel) of eggplant (Solanum melongena), using three extraction solvents: 70% methanol, 70% ethanol and 70% acetone. For each solvent, content of total phenolics, flavonoids, tannins, and total anthocyanins were quantified. Antioxidant activity of different extracts were screened using the ferric reducing power, 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging, hydrogen peroxide (H2O2) scavenging and metal chelating activities. The results showed that 70% methanol is the best solvent for the extraction of anthocyanins (82.83 ± 1.07 mg DGE/100 g DP), whereas, 70% acetone is the best solvent for the extraction of total phenolics, flavonoids and tannins (29.3 ± 1.23 mg GAE/100 g DE; 18.5 ± 0.07 mg QE/100 g DE and 5.37 ± 0.22 mg TAE/100 g DE, respectively). Anthocyanic extracts have exhibited the higher reducing power (39 ± 2.5 mg QE/100 g DE) and scavenging activity (IC50 = 2.88 ± 0.02 mg/mL), whereas the phenolic extracts have shown the highest metal chelating activity (18.53 ± 0.4%).