Tan, S.P.; Stathopoulos, C.; Parks, S.; Roach, P. An Optimised Aqueous Extract of Phenolic Compounds from Bitter Melon with High Antioxidant Capacity. Antioxidants 2014, 3, 814-829.
Abstract
Bitter melon (Momordica charantia L.) is a tropical fruit claimed to have medicinal properties associated with its content of phenolic compounds (TPC). The aim of the study was to compare water with several organic solvents (acetone, butanol, methanol and 80% ethanol) for its efficiency at extracting the TPC from freeze-dried bitter melon powder. The TPC of the extracts was measured using the Folin-Ciocalteu reagent and their antioxidant capacity (AC) was evaluated using three assays. Before optimisation, the TPC and AC of the aqueous extract were 63% and 20% lower, respectively, than for the best organic solvent, 80% ethanol. However, after optimising for temperature (80 °C), time (5 min), water-to-powder ratio (40:1 mL/g), particle size (1 mm) and the number of extractions of the same sample (1×), the TPC and the AC of the aqueous extract were equal or higher than for 80% ethanol. Furthermore, less solvent (40 mL water/g) and less time (5 min) were needed than was used for the 80% ethanol extract (100 mL/g for 1 h). Therefore, this study provides evidence to recommend the use of water as the solvent of choice for the extraction of the phenolic compounds and their associated antioxidant activities from bitter melon.
Conclusions
This study demonstrated that water could be used to effectively extract phenolic compounds and their associated antioxidant activities from bitter melon. It was shown that the aqueous method could be optimised to give an extraction equivalent to that obtained with the best organic solvent tested (80% ethanol) and less solvent and less time was required with water than with 80% ethanol. The optimal conditions for the aqueous extraction were a single extraction at 80 °C for 5 min at a water-to-powder ratio of 40:1 mL/g and a powder particle size of 1 mm. Therefore, this study provides evidence to recommend the use of water as the solvent of choice for the extraction of the phenolic compounds from bitter melon.
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