Optimized microwave extraction, characterization and antioxidant capacity of biological polysaccharides from Eucommia ulmoides Oliver leaf

Jikun Xu,Huijie Hou,Bingchuan Liu,Jingping Hu

doi:10.1038/s41598-018-24957-0

Jikun Xu, Huijie Hou + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-24957-0

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Abstract

Microwave-induced technique was combined with response surface methodology for optimizing the isolation of polysaccharides from Eucommia ulmoides Oliver leaf. The maximum polysaccharides yield of 12.31% was achieved by microwave extraction at 74 °C for 15 min with a solid to liquid ratio of 1:29 g/mL, which agreed with the predicted value and was 2.9-fold higher than that of the conventional heat-reflux extraction method. The dominant bioactive constituent in extracts was chlorogenic acid (1.3–1.9%), followed by geniposidic acid (1.0–1.7%). The polysaccharides from the optimized extraction had a high molecular weight and polydispersity (Mw 38,830 g/mol, Mw/Mn 2.19), as compared to the fraction prepared in the absence of microwave (Mw 12,055 g/mol, Mw/Mn 1.26). Glucose was the dominant sugar component (38.2–39.1%) of heterogeneous polysaccharides which belonged to a structure of β-type acidic heteropolysaccharides with a glucan group and highly branched degree. The polysaccharides showed a higher DPPH radical scavenging index (0.87–1.22) than BHT (0.41) but lower than BHA (3.56), which can act as a favorable antioxidant in functional food.

Highlights

Because of the potent nontoxic effects and therapeutic properties, the research on the biological polysaccharides and associated antioxidants from plant resources has attracted an increasing interest in the last decades with a diversified range of applications
In the current Box-Behnken design (BBD) of response surface methodology (RSM), a total of 17 runs were applied in the production of E. ulmoides leaf polysaccharides (EULP) to optimize the three individual parameters
To improve the yield of polysaccharides from E. ulmoides leaf, the microwave-assisted extraction (MAE) technology was combined with RSM for the optimization of extraction process

Summary

Introduction

Because of the potent nontoxic effects and therapeutic properties, the research on the biological polysaccharides and associated antioxidants from plant resources has attracted an increasing interest in the last decades with a diversified range of applications. The water-soluble polysaccharides and water extracts from Chinese traditional herb materials exhibited efficient bioactivities, including antioxidant, immunomodulation and anti-tumor, as reported by the previous studies[1,2,3,4]. RSM is an effective multivariate statistical method for optimizing complex experimental processes It generates a second-degree polynomial model by regression fitting of response surface analysis to evaluate the polytomy variables and its interaction, and determine the best level. A three-level and three variables BBD was used to model and optimize the extraction parameters (extraction temperature, time, and liquid to solid ratio) of polysaccharides by the MAE process for the elucidation of the different parameters that govern the extraction and structure of polysaccharides from E. ulmoides leaf. Analysis of the chemical compositions, structures, and antioxidant capacity of EULP was carried out by ultraviolet-visible spectroscopy (UV-Vis), sugar analysis, gel permeation chromatography (GPC), and Fourier transform infrared spectroscopy (FTIR) for unraveling the possibility of adopting the antioxidant polysaccharides to functional foods

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