Abstract
The fruit of Melastoma sanguineum Sims is an edible and sweet wild fruit. In our previous study, the fruit was found to have a strong antioxidant property. In this study, an ultrasound-assisted extraction (UAE) method was developed to extract natural antioxidants from the fruit of Melastoma sanguineum Sims, and a response surface methodology was used to optimize the conditions of UAE to maximize the extraction efficiency. The influence of five independent extraction parameters (ethanol concentration, solvent/material ratio, extracting time, temperature, and ultrasound power) on the extraction efficiency were investigated using a single factor experiment, and then a central composite rotatable design was used to investigate the interaction of three key parameters. The results showed that the optimal extraction conditions were 42.98% ethanol, 28.29 mL/g solvent/material ratio, 34.29 min extracting time, 60 °C temperature, and 600 W ultrasound power. Under these conditions, the Trolox equivalent antioxidant capacity (TEAC) value of the extracts was 1074.61 ± 32.56 μmol Trolox/g dry weight (DW). Compared with conventional maceration (723.27 ± 11.61 μmol Trolox/g DW) and Soxhlet extraction methods (518.37 ± 23.23 μmol Trolox/g DW), the UAE method improved the extraction efficiency, in a shorter period of time. In addition, epicatechin gallate, epicatechin, rutin, epigallocatechin, protocatechuic acid, chlorogenic acid, and quercetin, were identified and quantified in the fruit extracts of Melastoma sanguineum Sims by UPLC-MS/MS.
Highlights
Free radicals include reactive oxygen species (ROS), reactive sulfur species (RSS), and reactive nitrogen species (RNS) [1]
The results indicate that the extraction efficiency was improved with the increasing ultrasound power, but when the ultrasound power exceeded 600 W, some antioxidant components were possibly degraded, which was consistent with the other report [38]
The results show that the actual antioxidant activity changed from 591.72 to 1067.81 μmol Trolox/g dry weight (DW)
Summary
Free radicals include reactive oxygen species (ROS), reactive sulfur species (RSS), and reactive nitrogen species (RNS) [1]. In order to fully utilize the fruit of Melastoma sanguineum Sims, developing an efficient method to extract its antioxidants and identify the components of these extracts, is necessary. An UAE method was developed for extracting natural antioxidants from the fruit of Melastoma sanguineum Sims. Experiments were adopted to investigate the effects of five independent extraction parameters (ethanol concentration, solvent/material ratio, extracting time, temperature, and ultrasound power) on the extraction efficiency of natural antioxidants from the fruit of Melastoma sanguineum Sims, and a RSM with a five-level, three-variable central composite rotatable design (CCRD) was adopted, in order five-level, three-variable central composite rotatable design (CCRD) was adopted, in order to to study the interaction threekey keyextraction extractionparameters. Conditions, wereand identified andby quantified by liquid chromatography-tandem mass spectrometry
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