Alkaline Extraction, Structural Characterization, and Bioactivities of (1→6)-β-d-Glucan from Lentinus edodes.

Jia Li,Chao Cai,Jiejie Hao,Ya Wang,Mengmeng Zheng,Luodi Fan,Guangli Yu,Minghua Hu

doi:10.3390/molecules24081610

Abstract

The purpose of this study is to develop a robust approach to obtain β glucans from Lentinus edodes and to characterize their structural and biological properties for sustainable utilization. The alkali extraction was optimized with an orthogonal experimental design, and a concise process for obtaining specific targeting polysaccharides from Lentinus edodes was developed in this study. After purification with a Q-Sepharose Fast Flow strong anion-exchange column, the monosaccharide composition, a methylation analysis, and NMR spectroscopy were employed for their structural characterizations. LeP-N2 was found to be composed of (1→6)-β-d-glucans with minor β-(1→3) glucosidic side chains. Atomic force microscopy (AFM) and high-performance gel permeation chromatography–refractive index–multi-angle laser light scattering (HPGPC-RI-MALLS) also revealed LeP-N2 exhibiting a compact unit in aqueous solution. This (1→6)-β-d-glucan was tested for antioxidant activities with IC50 at 157 μg/mL. Moreover, RAW 264.7 macrophage activation indicated that the release of nitric oxide (NO) and reactive oxygen species (ROS) were markedly increased with no cytotoxicity at a dose of 100 μg/mL. These findings suggest that the (1→6)-β-d-glucans obtained from Lentinus edodes could serve as potential agents in the fields of functional foods or medicine.

Highlights

In recent years, polysaccharides have attracted considerable attention as bioactive ingredients and food additives in the medical and food industry [1,2]
The concentration of sodium hydroxide (NaOH) exerted the most significant effect (p < 0.05) on the extraction yields of crude polysaccharide, and the optimum alkaline extraction condition was determined to be in the solution of NaOH at 0.5 mol/L at 60 ◦ C for 2 h, which was according to the yield as an evaluation index
The optimized extraction of polysaccharides from Lentinus edodes was determined through an orthogonal design with an alkaline solution (NaOH, 0.1 mol/L) at 60 ◦ C for 2 h

Summary

Introduction

Polysaccharides have attracted considerable attention as bioactive ingredients and food additives in the medical and food industry [1,2]. The representative polysaccharides isolated from Chinese traditional herbs, including Ganoderma lucidum, Cordyceps, and Lentinus edodes, have been extensively studied due to their potent antitumor properties. Lentinan (LNT), a typical β-glucan isolated from the fruiting body of Lentinus edodes, has been widely used in clinics as an antitumor drug since its first use in Japan in the early 1980s. It possesses numerous bioactivities, such as anti-oxidation [6,7], antitumor activities [8,9], and immunomodulation [10,11]. Due to its unique triple helical conformation, the antitumor activity of lentinan is exerted not by a direct cytotoxic effect on cancer cells but prevalently through the activation of the host immune system, inducing macrophage and T-cell synergistic antitumor activities [5,12]

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