Total Monomeric Anthocyanin, Total Phenolic Content and Antioxidant Activity of Extracts from Eggplant (Solanum Melongena L.) Peel Using Ultrasonic Treatments

Abstract

AbstractEggplant peel is a less studied source in terms of bioactive compound extraction from industrial residues, although its high content of anthocyanin and phenolic compounds is known. The method described here uses three different solvents, namely ethanol, methanol and 2‐propanol, for phenol, anthocyanin and antioxidant activity extraction. The extraction yields of total monomeric anthocyanin (TMA), total phenolic compound (TPC) and antioxidant activity (AA) from eggplant peel were optimized by varying the frequency, temperature and time of ultrasonic treatment. The influence of interactions between process parameters on extraction efficiency was also studied. The highest concentrations achieved were 7.842 g/100g in the case of TPC (2‐propanol, 45 kHz, 60°C for 40 min), 2,275 mg/kg in the case of TMA (methanol, 45 kHz, 50°C for 50 min) and 10.18 μM Trolox/kg in the case of AA (methanol, 0 kHz, 60°C for 20 min). The suitable parameters to achieve the highest concentration of antioxidants were determined for each solvent as follows: ethanol – 28.8 kHz, 67.1°C and 49.5 min; methanol – 45 kHz, 50°C and 53.75 min; and 2‐propanol – 30.6 kHz, 70°C and 60 min.Practical ApplicationsThis study presents a significant improvement in eggplant peel extraction using ultrasonic‐assisted extraction of bioactive compounds. During ultrasonication, the extraction of bioactive compounds in eggplant peel increases because the solvent has been energized. The ultrasound‐assisted extraction of bioactive compounds is a fast, economical and green alternative to the current techniques used in the extraction industry.