Structural features, selenization modification, antioxidant and anti-tumor effects of polysaccharides from alfalfa roots
Introduction
Alfalfa (Medicago sativa L.) is a perennial forage crop belonging to the family Fabaceae and genus Medicago; it's widely distributed in Asia, Europe, and Oceania [1]. A mature alfalfa plant can reach the height of 100 cm with a deep, strong taproot and erect, sharply angled leafy stems [2]. Alfalfa is cultivated as an important industrial plant around the world because of its high yield and feeding value [3,4]. Studies suggested have shown that alfalfa stems are rich in polysaccharides with numerous activities, including antioxidant, anti-inflammatory, anti-tumor and lipid-lowering effects. [[4], [5], [6], [7]]. However, because the stem is the only consumable part of the plant, its root is often ignored; therefore, the polysaccharides from alfalfa roots have not been widely studied. Moreover, recent studies on alfalfa polysaccharide have mainly focused on its chemical structures, with few reports on its selenium modification. Thus, it is crucial to investigate the biochemical activities of polysaccharides from alfalfa roots and its selenium modification. This could boost the commercial utility and exploitation of the whole plant.
Selenium (Se) is a trace micronutrient with essential biological functions in the human body [8]. Consuming moderate amounts of Se can increase antioxidant effects and reduce the risk of cancer [9,10]. Compared with inorganic Se compounds, organic Se compounds coupled with proteins or polysaccharides are easily absorbed and exhibit antitumor effect [11,12]. Se-containing polysaccharides include synthesized selenium derivative of polysaccharides and natural selenium polysaccharides extracted from plants, which have stronger bioactivities than non-selenium polysaccharides [13]. Studies have revealed that modification of polysaccharides using selenium could alter their bioactivities and functions, such as antioxidant activity, tumor inhibition effect and anti-inflammatory function [13,14]. Hence, it can be used as an effective method to prepare new products with desirable features.
The objective of this study was to investigate the structural features, antioxidant activities and anti-tumor effects of two novel polysaccharides; RAPS-1 and RAPS-2 isolated from alfalfa roots alongside the selenium modified derivative Se-RAPS-2. This was achieved through the determination of Se content, weight-average molecular mass, identification of polysaccharides using UV, FT-IR, 1D- 2D-NMR methods, and antioxidant activities (ABTS, DPPH radicals-scavenging effects) as well as inhibition effect against HepG2 cells. This study serves as a reference for selenization modification and total utilization of alfalfa plants.
Section snippets
Materials and reagents
Fresh alfalfa plant roots were collected from Chifeng City (Inner Mongolia, China) in September 2016, after identification by Professor Jin-Cai Lu from Shenyang Pharmaceutical University. The voucher specimen (No. 2016-MSL) was kept in the College of Pharmaceutical and Biological Engineering, Shenyang University of Chemical Technology. Neutral protease, AB-8 resin, DEAE-52 cellulose and Sephadex G-200 columns were purchased from Ruida Henghui Co., Ltd. (Beijing, China). Dextrans of different
Purification and selenium modification of polysaccharide
The crude polysaccharide (CP) was separated using a DEAE-52 cellulose column to obtain two major fractions Fr.2 (56.5 mg, 0.17%) and Fr.3 (136.5 mg, 4.1%) with symmetrical elution profiles, which were eluted with 0.2 M and 0.3 M NaCl, respectively. Each fraction was sequentially purified by a Sephadex G-200 column to obtain two purified polysaccharides with single elution peaks, named RAPS-1 and RAPS-2. And their total carbohydrates were 92.5% and 97.1%, respectively (Fig. 1). Subsequently,
Conclusion
In summary, two novel polysaccharides (RAPS-1 and RAPS-2) were successfully isolated from alfalfa roots using DEAE-52 and Sephadex G-200 chromatography columns. Subsequently, a synthesized derivative (Se-RAPS-2) with 320 μg/g of Se was prepared by modifying native RAPS-2 using the HNO3/Na2SeO3 method. Structural analysis revealed that the molecular weights of RAPS-1, RAPS-2, Se-RAPS-2 were 10.0 kDa, 15.8 kDa, and 11.0 kDa, respectively. Unlike the alfalfa polysaccharides reported before, RAPS-1
Declaration of competing interest
We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, “Structural features, selenization modification, antioxidant and anti-tumor effects of polysaccharides from alfalfa roots”.
Acknowledgments
This study was supported by the Foundation (no. LQ2019010; L2016009) from the Project of Education Department of Liaoning Province of P. R. China, and the Foundation (no. 20170023) from the Project of Science and Technology Department of Liaoning Province of P. R. China.
References (45)
- et al.
Bioactive constituents from Medicago sativa L. with antioxidant, neuroprotective and acetylcholinesterase inhibitory activities
J. Funct. Food.
(2018) - et al.
Structural features, antioxidant and acetylcholinesterase inhibitory activities of polysaccharides from stem of Physalis alkekengi L
Ind. Crop. Prod.
(2019) - et al.
Optimization of enzyme-assisted extraction of polysaccharides from alfalfa and its antioxidant activity
Int. J. Biol. Macromol.
(2013) - et al.
Purification, characterisation and protective effects of polysaccharides from alfalfa on hepatocytes
Carbohydr. Polym.
(2014) - et al.
Extraction, preliminary characterization and antioxidant activity of Se-enriched Maitake polysaccharide
Carbohydr. Polym.
(2014) - et al.
Selenium-dependent antitumor immunomodulating activity of polysaccharides from roots of A. membranaceus
Int. J. Biol. Macromol.
(2014) The importance of selenium to human health
Lancet
(2000)- et al.
Induction of mitochondrial-dependent apoptosis in T24 cells by a selenium (Se)-containing polysaccharide from Ginkgo biloba L. leaves
Int. J. Biol. Macromol.
(2017) - et al.
Synthesis, characterization, antioxidant activity and neuroprotective effects of selenium polysaccharide from Radix hedysari
Carbohydr. Polym.
(2015) - et al.
Antihyperlipidemic and hepatoprotective properties of selenium modified polysaccharide from Lachnum sp
Int. J. Biol. Macromol.
(2017)
Characterization, antioxidant and immunomodulatory activities of polysaccharides from Prunella vulgaris Linn
Int. J. Biol. Macromol.
Preparation, structural characterization and bioactivities of Se-containing polysaccharide: a review
Int. J. Biol. Macromol.
Fractionation, preliminary structural characterization and bioactivities of polysaccharides from Sargassum pallidum
Carbohydr. Polym.
Use of a free radical method to evaluate antioxidant activity
LWT-Food SCI Technol
Quantification of sugars and organic acids in tomato fruits
MethodsX
Purification, characterization, and bioactivities of a polysaccharide from mycelial fermentation of Bjerkandera fumosa
Carbohydr. Polym.
The effect of ultrasound assisted extraction on structural composition, antioxidant activity and immunoregulation of polysaccharides from Ziziphus jujuba Mill var. spinosa seeds
Ind. Crop. Prod.
Antioxidant activity and optimization of extraction of polysaccharide from the roots of Dipsacus asperoides
Int. J. Biol. Macromol.
Structural elucidation of a water-soluble polysaccharide isolated from Balangu shirazi (Lallemantia royleana) seeds
Food Hydrocoll.
Anti-fatigue activity of polysaccharide fractions from Lepidium meyenii Walp. (maca)
Int. J. Biol. Macromol.
The core carbohydrate structure of Acacia seyal var. seyal Gum arabic
Food Hydrocoll.
Structural characterization and conformational properties of a polysaccharide isolated from Dendrobium nobile Lindl
Food Hydrocoll.
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