Microwave-Assisted Extraction of Natural Antioxidants from the Exotic Gordonia axillaris Fruit: Optimization and Identification of Phenolic Compounds

Abstract

Our previous study reported that the fruit of Gordonia axillaris, an edible wild fruit, possessed strong antioxidant activity. In this study, a microwave-assisted extraction (MAE) method was established to extract antioxidants from the fruit of Gordonia axillaris. The influence of five parameters, including ethanol concentration, solvent/material ratio, extraction time, extraction temperature and microwave power, was investigated by single-factor experiments. Three factors, namely ethanol concentration, solvent/material ratio, extraction time, were found to exert a major influence on extraction efficacy, and were further studied by response surface methodology to investigate their interactions. Ethanol concentration of 36.89%, solvent/material ratio of 29.56 mL/g, extraction time of 71.04 min, temperature of 40 °C, and microwave power of 400 W were found to be the optimal condition. The TEAC value was 198.16 ± 5.47 µmol Trolox/g DW under the optimal conditions, which was in conformity to the predicted value (200.28 µmol Trolox/g DW). In addition, the MAE method was compared with two conventional methods (Soxhlet extraction and maceration extraction). Results showed that the antioxidant capacity of the extract obtained by MAE method was stronger than that obtained by maceration (168.67 ± 3.88 µmol Trolox/g DW) or Soxhlet extraction (114.09 ± 2.01 µmol Trolox/g DW). Finally, several phenolic compounds in the extract were identified and quantified by UPLC-MS/MS, which were rutin, gallic acid, protocatechuic acid, epicatechin, epicatechin gallate, 2-hydrocinnamic acid, p-coumaric acid, quercetin, chlorogenic acid and ferulic acid.

Mixture Design and Doehlert Matrix for the Optimization of the Extraction of Phenolic Compounds from Spondias mombin L Apple Bagasse Agroindustrial Residues

“…In addition, the analysis of the residues generated between the predicted values and the observed values, the coefficient determination value (0.9448) and adjust coefficient of determination value (0.8988) indicated a good predictability of the model. Li et al ( 2017 ) established a microwave-assisted extraction (MAE) method to extract antioxidants from the fruit of Gordonia axillaris, and the method was compared with two conventional methods (Soxhlet extraction and maceration extraction). The antioxidant capacity of the extract determined by MAE was stronger than those obtained by Soxhlet extraction (114.1 ± 2.0 μmol Trolox/g DW) or maceration (168.7 ± 3.9 μmol Trolox/g DW) (Li et al, 2017 ).…”

Extraction, Partial Identification and Bioactivities of Total Flavonoids from Carex meyeriana Kunth

“…At above 60°C, the extraction rate began to decline. Due to the fact that low temperature dose not facilitate the diffusion of molecules, leading to the incompletion of extraction, while high temperature is prone to cause the degradation of bioactive constituents, both of which can induce the decrease of extraction yield (Ya et al, 2017).…”

Comparison of Microwave and Ultrasonic Assisted Extraction of Kaempferol from Cassia Alata

“…However, too much temperature increment at higher MAE power causes a thermal degradation of kaempferol, hence reducing its yield. Li et al [27] also found that excessive microwave power causes the degradation of some antioxidants, and hence adversely affecting the extraction yield. The highest kaempferol yield (21.55 mg/g DW) from C. alata was achieved at microwave power of 100 W.…”