Structural and Biological Properties of Water Soluble Polysaccharides from Lotus Leaves: Effects of Drying Techniques

Abstract

In the present study, the influence of five drying techniques on the structural and biological properties of polysaccharides from lotus leaves (LLPs) was investigated. Results revealed that the yields, contents of basic chemical components, molecular weights, and molar ratios of compositional monosaccharides of LLPs varied by different drying technologies. Low molecular weight distributions were observed in polysaccharides obtained from lotus leaves by hot air drying (LLP-H), microwave drying (LLP-M), and radio frequency drying (LLP-RF), respectively. The high contents of bound polyphenolics were measured in LLP-H and LLP-M, as well as polysaccharides obtained from lotus leaves by vacuum drying (LLP-V). Furthermore, both Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra of LLPs were similar, indicating that drying technologies did not change their basic chemical structures. Besides, all LLPs exhibited obvious biological properties, including in vitro antioxidant capacities, antiglycation activities, and inhibitory effects on α-glucosidase. Indeed, LLP-H exhibited higher 2,2-azidobisphenol (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging ability (IC50 values, LLP-H, 0.176 ± 0.004 mg/mL; vitamin C, 0.043 ± 0.002 mg/mL) and 2,2-diphenyl-1-(2,4,6-trinitrate phenyl) hydrazine radical scavenging ability (IC50 values, LLP-H, 0.241 ± 0.007 mg/mL; butylated hydroxytoluene, 0.366 ± 0.010 mg/mL) than others, and LLP-M exerted stronger antiglycation (IC50 values, LLP-M, 1.023 ± 0.053 mg/mL; aminoguanidine, 1.744 ± 0.080 mg/mL) and inhibitory effects on α-glucosidase (IC50 values, LLP-M, 1.90 ± 0.02 μg/mL; acarbose, 724.98 ± 16.93 μg/mL) than others. These findings indicate that both hot air drying and microwave drying can be potential drying techniques for the pre-processing of lotus leaves for industrial applications.

In vitro digestive characteristics and microbial degradation of polysaccharides from lotus leaves and related effects on the modulation of intestinal microbiota

“…The digestive characteristics of LLP's molecular weight was similar to the results of several previous studies, such as polysaccharides extracted from tamarind seed, Fuzhuan brick tea, and Flammulina velutipes ( Chen et al, 2018b ; Li et al, 2020 ; Su et al, 2019 ). Moreover, total polysaccharides and total uronic acids existing in LLP were detected to be 82.35% and 39.44%, respectively, which were in agreement with previously reported results ( Li et al, 2021 ; Song et al, 2019 ; Wu et al, 2021a ). After the in vitro digestion, total polysaccharides and uronic acids in LLP were basically unchanged ( Table 2 ), which retained 79.91% - 81.29%, and 38.95% - 39.65%, respectively.…”

“…2 B, the FT-IR spectra of LLP at different digested stages in the upper gastrointestinal tract in vitro were similar, indicating that the primarily chemical structure of LLP was overall stable. Additionally, the typical signals of acidic polysaccharides, including 3432, 2952, 1744, 1611, 1429, 1240, and 890 cm −1 , were found in LLP and its digested samples ( Li et al, 2021 ; Wu et al, 2021a ). In addition, as shown in Table 1 , the DE values of LLP, LLPS, LLPG, and LLPI were similar, which ranged from 27.75% to 28.80%.…”

“…The major constituent monosaccharides in polysaccharides from louts leaves include galactose, galacturonic acid, arabinose, rhamnose, mannose, glucose, and glucuronic acid, indicating that homogalacturonan (HG), rhamnogalacturonan I (RG I), and arabinogalactan (AG) exist in lotus leaves ( Huang et al, 2021 ; Wu et al, 2021a ). Furthermore, these pectic polysaccharides from lotus leaves also possess diversely beneficial effects, such as antioxidant, anti-glycation, anti-cancer, anti-diabetic, and immunomodulatory effects ( Huang et al, 2021 ; Li et al, 2021 ; Song et al, 2019 ; Wu et al, 2021a ; Zeng et al, 2017 ; Zhang et al, 2015 ). Collectively, these studies suggest that lotus leaf polysaccharides (LLP) possess potential applications in the functional food industry.…”

Deep Eutectic Solvent-Assisted Extraction, Partially Structural Characterization, and Bioactivities of Acidic Polysaccharides from Lotus Leaves

“…Lotus leaves (Nelumbo nucifera Gaertn) were collected from Meishan, Sichuan Province, China. Lotus leaves were dried by hot wind at 75 • C for 7 h according to a previous study [6], and then pulverized into powder.…”

“…Generally, these health benefits are associated with a variety of bioactive components that exist in lotus leaves, such as polysaccharides, phenolic compounds, alkaloids, and essential oils [2]. Among them, polysaccharides, as the essentially bioactive components in lotus leaves, also possess various health-promoting effects, such as anti-diabetic, antioxidant, antiglycation, and immunostimulatory effects [3][4][5][6][7]. Therefore, all data cited above indicates that polysaccharides extracted from lotus leaves exhibit good application potentials in the functional food industry.…”