Ultrasonic-Assisted Extraction of α-Tocopherol Antioxidants from the Fronds of Elaeis guineensis Jacq.: Optimization, Kinetics, and Thermodynamic Studies

This article presents the first report on the extraction and quantification of α-tocopherol from the fronds of the oil palm (Elaeis guineensis Jacq). In this study, the optimization, kinetic, and thermodynamic data of α-tocopherol extraction by sonication are presented. Response surface methodology coupled with central composite design was used to optimize the experimental conditions for α-tocopherol extraction. Three independent variables, namely sample/solvent ratio (1:20–1:40 g/ml), extraction temperature (30–50 °C), and extraction time (20–50 min) were studied. For optimum conditions of 39.31 °C (~40 °C), 50 min, and 1:23.63 g/mL (~1:20 g/mL), total tocols and α-tocopherol optimal concentrations were 346.49 μg/g oil palm fronds (OPFs) by dry weight (DW) and 28.41 μg/g OPF DW, respectively. The effects of extraction temperature and tocol concentrations on the extraction kinetics and thermodynamic parameters were also studied. From the mass transfer rate equation, the kinetic and thermodynamic data obtained from the ultrasonic-assisted extraction (UAE) of α-tocopherol from OPF were activation energy, E _a (104.6 kJ mol^?1), UAE rate constant, k (6.886?×?10^?3 min^?1), ΔH (+0.818 kJ mol^?1), ΔS (+27.22 J mol^?1 K^?1), and ΔG (?8.52 J mol^?1). According to this study, the UAE of α-tocopherol from OPF is endothermic, irreversible, and spontaneous.