Abstract
In this study, the effects of microwave-assisted extraction conditions on antioxidant capacity of sweet tea (Lithocarpus polystachyus Rehd.) were studied and the antioxidants in the extract were identified. The influences of ethanol concentration, solvent-to-sample ratio, microwave power, extraction temperature and extraction time on Trolox equivalent antioxidant capacity (TEAC) value, ferric reducing antioxidant power (FRAP) value and total phenolic content (TPC) were investigated by single-factor experiments. The response surface methodology (RSM) was used to study the interaction of three parameters which had significant influences on antioxidant capacity including ethanol concentration, solvent-to-sample ratio and extraction time. The optimal conditions for the extraction of antioxidants from sweet tea were found as follows—ethanol concentration of 58.43% (v/v), solvent-to-sample ratio of 35.39:1 mL/g, extraction time of 25.26 min, extraction temperature of 50 ℃ and microwave power of 600 W. The FRAP, TEAC and TPC values of the extract under the optimal conditions were 381.29 ± 4.42 μM Fe(II)/g dry weight (DW), 613.11 ± 9.32 μM Trolox/g DW and 135.94 ± 0.52 mg gallic acid equivalent (GAE)/g DW, respectively. In addition, the major antioxidant components in the extract were detected by high-performance liquid chromatography with diode array detection (HPLC-DAD), including phlorizin, phloretin and trilobatin. The crude extract could be used as food additives or developed into functional food for the prevention and management of oxidative stress-related diseases.
Highlights
Sweet tea comes from the leaves of the evergreen tree Lithocarpus polystachyus Rehd. and its taste is sweet [1]
We evaluated the antioxidant activity of sweet tea extracts by ferric-reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays and measured the total phenol content (TPC) of the extracts
ferric reducing antioxidant power (FRAP) values were observed to rise between 20–50% (v/v) of ethanol concentration and fall from 50% (v/v)
Summary
Sweet tea comes from the leaves of the evergreen tree Lithocarpus polystachyus Rehd. and its taste is sweet [1]. Sweet tea comes from the leaves of the evergreen tree Lithocarpus polystachyus Rehd. Its taste is sweet [1]. Sweet tea has already been approved as new food materials in China since 2017. Sweet tea contains various bioactive ingredients, such as polyphenols and polysaccharides, especially flavonoids [2]. The main flavonoids in sweet tea are dihydrochalcones, including phlorizin, phloretin and trilobatin. These compounds are the main bioactive components of sweet tea and major contributors to its sweetness [3]. Sweet tea and its bioactive components have been found to have antioxidant, Antioxidants 2020, 9, 678; doi:10.3390/antiox9080678 www.mdpi.com/journal/antioxidants
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
