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

Ya Li,Hua-Bin Li,Jiao-Jiao Zhang,Cai-Ning Zhao,Sha Li,Sheng-Jun Lin

doi:10.3390/molecules22091481

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.

Highlights

In recent years, free radicals, including reactive oxygen species (ROS) and reactive nitrogen species (RNS), have gained increasing attention [1]
The results showed that the antioxidant capacity varied from 43.27 to 196.88 μmol Trolox/g DW
A microwave-assisted extraction method coupled with response surface methodology (RSM) has been developed in the present study to extract antioxidants from the fruit of Gordonia axillaris and to optimize the extraction conditions

Summary

Introduction

Free radicals, including reactive oxygen species (ROS) and reactive nitrogen species (RNS), have gained increasing attention [1]. Excessive free radicals could induce oxidative damage, which may partly contribute to various human diseases, such as cancer and neurodegenerative. Molecules 2017, 22, 1481 disease [3,4]. Many natural products, such as fruits, vegetables and edible flowers, have been found to be rich in antioxidants and exhibit great antioxidant capacity in vitro [5,6,7,8,9,10,11,12,13]. Studies on thedisease extraction of these are and of great [3,4]. Flowers, have been found to Gordonia be rich in antioxidants and exhibit great antioxidant capacity in vitro. 1) belongs to the Theaceae family [14].[5,6,7,8,9,10,11,12,13].

Methods

Results

Conclusion