Abstract
This study is the first to report the use of response surface methodology to improve phenolic yield and antioxidant activity of Acer truncatum leaves extracts (ATLs) obtained by ultrasonic-assisted extraction. The phenolic composition in ATLs extracted under the optimized conditions were characterized by UPLC-QTOF-MS/MS. Solvent and extraction time were selected based on preliminary experiments, and a four-factors-three-levels central composite design was conducted to optimize solvent concentration (X1), material-to-liquid ratio (X2), ultrasonic temperature (X3) and power (X4) for an optimal total phenol yield (Y1) and DPPH• antioxidant activity (Y2). The results showed that the optimal combination was ethanol:water (v:v) 66.21%, material-to-liquid ratio 1:15.31 g/mL, ultrasonic bath temperature 60 °C, power 267.30 W, and time 30 min with three extractions, giving a maximal total phenol yield of 7593.62 mg gallic acid equivalent/100 g d.w. and a maximal DPPH• antioxidant activity of 74,241.61 μmol Trolox equivalent/100 g d.w. Furthermore, 22 phenolics were first identified in ATL extract obtained under the optimized conditions, indicating that gallates, gallotannins, quercetin, myricetin and chlorogenic acid derivatives were the main phenolic components in ATL. What’s more, a gallotannins pathway existing in ATL from gallic acid to penta-O-galloylglucoside was proposed. All these results provide practical information aiming at full utilization of phenolics in ATL, together with fundamental knowledge for further research.
Highlights
Acer truncatum is a prominent maple (Aceraceae) species widely cultivated in China, Korea andJapan, and is found in Europe and Northern America [1,2]
In order to ensure the full utilization of Acer truncatum leaves extracts (ATLs), in the current study an ultrasound-assisted extraction (UAE) method was established through response surface methodology (RSM)
To the best of our knowledge, the other 22 phenolics were firstly discovered in the present study. These findings provided the fundamental information to characterization of the phenolic compositions in ATL, and signified the superiority of the UAE condition optimized to a certain extent
Summary
Acer truncatum is a prominent maple (Aceraceae) species widely cultivated in China, Korea andJapan, and is found in Europe and Northern America [1,2]. In northern China, maple leaves, mainly A. truncatum leaves (ATL), are often used as health drinks and folk medicines for treating coronary artery cirrhosis, cerebrovascular diseases and angina pectoris [3]. Little effort has been made to optimize of methods of extraction of phenolics from ATL. In order to ensure the full utilization of ATL, in the current study an ultrasound-assisted extraction (UAE) method was established through response surface methodology (RSM). Compared to other conventional methods, UAE offers a net advantage in terms of productivity and selectivity with shorter processing times, enhanced quality, reduced chemical and physical hazards, and it is environmentally friendly and causes less damage to the structural and molecular properties of compounds in plant materials [9,10]
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