Extraction of phenolic compound from fruits of bitter melon (Momordica charantia) with subcritical water and antioxidant activities

Abstract

Bitter melon (Momordica charantia) is traditionally known for its medicinal properties such as antidiabetic, anticancer, anti-inflammation, antivirus, and cholesterol lowering effects. It contains many phenolic compounds that may have the potential as antioxidant and antimutagen. Although the value of bitter melon is realized, scientific information on phenolic composition of bitter melon and antioxidant and antimutagenic activities of its extracts from food grade solvents are limited. This study were investigated the total phenolic contents of bitter melon obtained by subcritical water extraction (SCWE) and antioxidant activities of these extracts. The effects of extraction temperature and water flow rate were considered and the results were compared with the extracts obtained by solvent extraction and soxhlet extraction. The subcritical water extraction of the total phenolic contents in bitter melon was carried out at the temperature between 130 degrees Celsius to 200 degrees Celsius and the effect of water flow rate was investigated in the range of 2 to 5 ml/min, while the constant pressure of 10 MPa. The most suitable extraction condition was found to be at the temperature of 150-200 degrees Celsius and flow rate of 2 ml/min. The total phenolic contents of bitter melon obtained by the SCWE, the solvent extraction, and soxhlet extraction were 52.63, 6.00, and 6.68 mg gallic acid equivalents (GAE)/g dry weight (DW), respectively. Overall, the extract obtained by SCWE was significantly higher than solvent extraction and soxhlet extraction. The most phenolic acids contained in bitter melon were catechin. Catechin was calculated from HPLC analysis of the extracts from bitter melon obtained by the SCWE, the solvent extraction, and soxhlet extraction were 46.16, 1.61, and 1.77 mg/g DW, respectively. The subcritical water extraction at lower temperature gave higher antioxidant activity than the extracts obtained at higher temperature. The extract obtained by subcritical water extraction gave the higher antioxidant activity than solvent extraction, and soxhlet extraction. Even though the total phenolic contents between extraction method and extraction temperature were significantly different, their different antioxidant activities indicated that antioxidant activity was not depended only by their total phenolic contents. Thus, bitter melon is a good source of phenolic compounds and has high potent antioxidant activity.