Enhanced recovery of phenolic compounds from bitter melon (Momordica charantia) by subcritical water extraction

In this study, enhanced recovery of phenolic compounds from bitter melon (Momordica charantia) was achieved by subcritical water extraction (SWE). The extraction was carried out at a constant pressure of 10 MPa and the effects of extraction temperature (130–200 °C) and water flow rate (2–5 ml/min) were determined on the amount of phenolic compounds and the most suitable extraction condition was found to be at the temperature between 150 and 200 °C and at the flow rate of 2 ml/min. The amount of phenolic compounds in the extracts obtained by SWE (52.63 mg gallic acid equivalents (GAE)/g dry weight (DW)) was significantly higher than those in the extracts obtained by MeOH extraction (5.00–6.00 mg GAE/g DW) and soxhlet water extraction (5.00–7.00 mg GAE/g DW). The most phenolic acids contained in bitter melon were catechin, whose content in the extracts obtained by the SWE, MeOH extraction, and soxhlet extraction were 46.16, 1.61, and 1.77 mg/g DW, respectively. Although the amount of phenolic compounds in the extracts obtained by SWE at lower temperature was found to be lower than those obtained at higher temperature, they exhibited higher antioxidant activity. Nevertheless, all extracts obtained with SWE had approximately threefold higher antioxidant activity than those obtained by extraction with MeOH or water at ambient pressure conditions.