Microwave-Assisted Deep Eutectic Solvent Extraction, Structural Characteristics, and Biological Functions of Polysaccharides from Sweet Tea (Lithocarpus litseifolius) Leaves

Abstract

The leaf of sweet tea (Lithocarpus litseifolius) is widely used as an edible and medicinal plant in China, which is rich in bioactive polysaccharides. In order to explore and promote the application of sweet tea polysaccharides in the functional food industry, the microwave-assisted deep eutectic solvent extraction (MDAE) of polysaccharides from sweet tea leaves was optimized, and the structural properties and biological functions of sweet tea polysaccharides prepared by MDAE (P-DM) were investigated and compared with that of hot water extraction (P-W). The maximum yield (4.16% ± 0.09%, w/w) of P-DM was obtained under the optimal extraction conditions (extraction time of 11.0 min, extraction power of 576.0 W, water content in deep eutectic solvent of 21.0%, and liquid–solid ratio of 29.0 mL/g). Additionally, P-DM and P-W possessed similar constituent monosaccharides and glycosidic bonds, and the homogalacturonan (HG) and arabinogalactan (AG) might exist in both P-DM and P-W. Notably, the lower molecular weight, higher content of total uronic acids, and higher content of conjugated polyphenols were observed in P-DW compared to P-W, which might contribute to its much stronger in vitro antioxidant, anti-diabetic, antiglycation, and prebiotic effects. Besides, both P-DW and P-W exhibited remarkable in vitro immunostimulatory effects. The findings from the present study indicate that the MDAE has good potential to be used for efficient extraction of bioactive polysaccharides from sweet tea leaves and P-DM can be developed as functional food ingredients in the food industry.

Effects of various degrees of esterification on antioxidant and immunostimulatory activities of okra pectic-polysaccharides

“…However, in this study, the decrease of DE value was mainly attributed to the de-acetylation of galacturonosyl residues in OPP ( Figure 2 ), which might not obviously affect the rate of unmethylated uronic acids. Besides, the antioxidant capacity of pectic-polysaccharides is often closely related to their molecular mass and uronic acids ( 12 , 15 , 36 , 41 ). Therefore, in this study, according to the structural differences measured as abovementioned, the slight decrease of antioxidant activity of DOPP-LDE compared to DOPP-HDE might be due to the slight decrease of uronic acid content ( Table 1 ).…”

The Most Potent Natural Pharmaceuticals, Cosmetics, and Food Ingredients Isolated from Plants with Deep Eutectic Solvents

“…Similar properties were demonstrated for polysaccharides from Lithocarpus litseifolius leaves. In addition, these compounds could be applied in diabetes treatment . Polysaccharides extracted from lotus leaves were examined in terms of their antioxidant capacities.…”

“…In addition, these compounds could be applied in diabetes treatment. 235 Polysaccharides extracted from lotus leaves were examined in terms of their antioxidant capacities. Through extraction with DESs, the antioxidant properties of compounds were more intense compared to the extracts isolated with water.…”

Process optimization of deep eutectic solvent-based microwave-assisted extraction of flavonoids from Ziziphi Spinosae Semen using response surface methodology

“…The single-factor experimental design was carried out to evaluate the effects of the water content of DES (30, 40, 50, 60, 70%), microwave power (400, 500, 600, 700, 800 W), microwave radiation time (30, 60, 90, 120, 150 s), material-to-liquid ratio (1:15, 1:20, 1:25, 1:30, 1:35 mg/g), extraction temperature (60, 70, 80, 90, 100 °C) and extraction time (40, 50, 60, 70, 80 min) on the yield of total flavonoids in ZSS, respectively. In determining these specific ranges of values, we have benefited from the existing knowledge on the extraction of flavonoids from previous studies (Pal & Jadeja, 2019;Wu et al, 2022).…”

“…Currently, DES has been widely used to extract active ingredients of traditional Chinese medicine, such as flavonoids, phenolic acids, and alkaloids. When using DES to extract flavonoids, higher yields were always obtained than conventional solvents (Wu et al, 2022). However, most DESs exhibit viscosities higher than many conventional organic solvents, which is not conducive to the rapid diffusion of target components.…”