Elsevier

Industrial Crops and Products

Volume 168, 15 September 2021, 113547
Industrial Crops and Products

Polysaccharides isolated from Lycium barbarum L. by integrated tandem hybrid membrane technology exert antioxidant activities in mitochondria

https://doi.org/10.1016/j.indcrop.2021.113547Get rights and content

Highlights

  • Integrated tandem hybrid membrane technology can separate plant polysaccharides.

  • Four polysaccharide fractions were isolated from Lycium barbarum L.

  • L. barbarum polysaccharides showed different physicochemical and antioxidant ability.

  • L. barbarum polysaccharides exert antioxidant effects in mitochondria.

Abstract

Variations in the molecular weight (MW) of polysaccharides may lead to different pharmacological functions. Hierarchical alcohol precipitation is presently the most popular method of separating polysaccharides. However, as polysaccharide molecules in solution becomes dehydrated in ethanol, the conformation transforms and becomes assembled via intramolecular hydrogen bonding, which can complicate studies on the biological activities of polysaccharides. This work developed an integrated tandem hybrid membrane technology (ITHMT) to separate polysaccharides extracted from Lycium barbarum L. into fractions. The polysaccharide fractions LBP1, LBP2, LBP3, and LBP4 were separated using ITHMT. Preliminary structural analysis including homogeneity, molecular weight, monosaccharide composition, scanning electron microscopy and thermogravimetric analysis were investigated. Both LBP3 and LBP4 had symmetrical single peaks and were considered as one homogeneous polysaccharide. A lower MW cut-off for membrane elements was associated with increased polysaccharide homogeneity. LBP1∼LBP4 were found to be heteropolysaccharides and comprised rhamnose, galactose, glucose, mannose, and galacturonic acid with different molar ratios and MW. The MW of LBP1∼LBP4 were 225.6 kDa, 140.2 kDa, 65.0 kDa, and 38.3 kDa, respectively. Four polysaccharide fractions had unique morphologies, good thermal stabilities and different antioxidant effects. The LBP4 fraction exerted significant antioxidant effects against superoxide anion radicals and ferric-reducing antioxidant effect in vitro, as well as superoxide anion radicals in vivo, indicated L. barbarum polysaccharides with different molecular weight did had different antioxidant activity. All polysaccharides reduced the levels of superoxide anions in mitochondria but could not scavenge cytoplasmic H2O2, indicating that the antioxidant capacity of L. barbarum polysaccharides is achieved through the removal of superoxide anions from intracellular mitochondria.

Introduction

Lycium barbarum L. (wolfberry, Goji berries) have been recognized and used as a valuable traditional Chinese herbal medicine and functional food for 2500 years. The earliest record of these berries is found in the oracle bone script (Jiaguwen) of the Shang Dynasty (1600–1040 BE). The medicinal properties of Lycium barbarum L. have been appreciated by numerous medical scientists throughout the history of China. Medical and pharmaceutical knowledge regarding L. barbarum, which are categorized among the top class of medicines and contribute to longevity, have been recorded and summarized in Shennong’s Root and Herbal Classic (Shennong bencao jing). Li Shizhen also summarized the health and tonic effects of Goji berries in the Compendium of Materia Medica (Wu et al., 2018; Li, 2007; Chiu et al., 2010).

The most important active ingredients in Lycium barbarum L. are complexes of polysaccharides and glycoproteins, followed by flavonoids, carotenoids, saponins and others (Zhou et al., 2017; Pires et al., 2018; Kan et al., 2020). Polysaccharides with a molecular weight (MW) of 10–2300 kDa comprise 5%–8% of the dried fruits and possess hypoglycemic, hypolipidemic, immuno-modulatory, antioxidant, anti-aging, neuroprotective, and anti-Alzheimer’s disease properties (Tian et al., 2019; Yao et al., 2018; Masci et al., 2018; Kwok et al., 2019). The varied MW of polysaccharides may lead to different pharmacological functions. Zhou et al. degraded extracellular polysaccharides (EPS) with MW of 6.53, 256, 606, 802.6, 903.3, and 1002 kDa by hermetical–microwave and H2O2 under ultrasonic waves, and observed notable differences among their activities; in particular, the 6.53 kDa fraction had the most potent immune enhancing activity (Sun et al., 2012). Sun et al. obtained four low molecular polysaccharides derivatives (CPA-1, CPA-2, CPA-3 and CPA-4) by adding increased proportions of hydrogen peroxide, and have confirmed that high MW polysaccharides could scavenge free DPPH radicals and possess significant reducing ability, whereas the low MW polysaccharides exhibit relatively more potent free radical scavenging activity, especially for hydroxyl radicals (Sheng and Sun, 2014). Gu et al. successively fractionated the following polysaccharides using ethanol: SPC-60 (52.0 kDa), SPC-70 (294.9 kDa), SPC-80 (230.6 kDa), and SPC-90 (229.4 kDa); among these, SPC-70 was the most potent scavenger of DPPH, ABTS, and hydroxyl radicals, whereas SPC-60 exhibited the strongest immunomodulatory effects in terms of phagocytosis, proliferation activity, and nitric oxide (NO) release (Gu et al., 2019).

At present, the hierarchical alcohol precipitation method is the main method that can separate polysaccharides into different fragments. Polysaccharides fractions with different average molecular weight can be precipitated by different concentrations of ethanol. When ethanol is added to a solution containing polysaccharide, the polysaccharide molecules begin to dehydrate, followed with conformation transforming and assembling, caused by the enhancement of intramolecular hydrogen bonding. This may make it difficult to study the biological activity of polysaccharides themselves (Jiang et al., 2019; Wang et al., 2019). Membrane separation technology has rapidly advanced over the past few years. High separation efficiency, low energy consumption, rapid procedure, simple operation, and no contamination are critical to maintaining the original chemical structures and bioactivities of the extracted components, and membrane techniques have proven efficient for separating carbohydrates (Córdova et al., 2017). Zhang et al. isolated soybean oligosaccharides using two nanofiltration (NF) membranes with a yield and purity of 83.2 % and 77.9 %, respectively (Zhao et al., 2017). Nabarlatz et al. achieved optimal isolation of xylooligosaccharides from amylopectin acidification products using a 1000 Da membrane (Nabarlatz et al., 2007). Sun et al. used integrated membrane technology with nanofiltration, ultrafiltration, and microfiltration membranes to fractionate crude oligosaccharides from Hericium erinaceus (Cai et al., 2019). However, membrane separation technology has not yet been applied to separate polysaccharides from L. barbarum.

This work developed and applied a novel integrated tandem hybrid membrane technology (ITHMT) to separate L. barbarum polysaccharides having different MW. Four polysaccharides fractions (LBP1, LBP2, LBP3, and LBP4) were successfully isolated from L. barbarum. Further, the structures and antioxidant capacities of the isolated polysaccharides were preliminarily analyzed.

Section snippets

Materials and chemicals

Dried fruits of Lycium barbarum were gathered from Ningxia Zhongqi Wolfberry Trading Group Co., Ltd. on 1 May 2017, kept dry, and ventilated and were discerned by Dr. Xiao-Dong Luo from Kunming Institute of Botany, CAS. A specimen was stored at the Lanzhou Institute of Chemical Physics, CAS, with a serial number of 20170501. The test report from Alex Stewart Agriculture LTD showed that the specimen contained 4.01 % polysaccharides, 5.75 % water, 46.5 % carbohydrates, 13.5 % protein and 3.0 %

Preparation of crude L. barbarum polysaccharides

Goji berries contain abundant pigments such as carotenoids, which must be removed before extracting L. barbarum polysaccharides. The pigments were removed from Goji berries using subcritical extraction technology. The advantages of this procedure include a high extraction yield, rapid processing, and simple operation; moreover, since heat and radiation are not required in this procedure, the original chemical structures and bioactivities of the extracted components are retained, and so, this

Conclusions

The study established a novel ITHMT method for the separation of polysaccharides based on the principle of molecular exclusion. As a result, four polysaccharide fractions (LBP1, LBP2, LBP3 and LBP4) with different physiochemical properties were successfully isolated from L. barbarum L. All of them concentration-dependently scavenged superoxide anion radicals, and increased reducing power in vitro, as well as reduced the level of superoxide anions in mitochondria. This indicated that the

CRediT authorship contribution statement

Jianfei Liu: Data curation, Writing - original draft. Qiaosheng Pu: Writing - review & editing. Hongdeng Qiu: Software, Validation. Duolong Di: Supervision, Conceptualization, Methodology.

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (No. 21904130) and the Science and Technology Program of Gansu Province (20CX9FG238). The authors also are grateful to Meng Jiao from National Laboratory of Biomacromolecules (CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences) for their support about Effect of Lycium barbarum polysaccharide on ROS in different organelles and anonymous reviewers for their

References (41)

  • Y.Y. Jiang et al.

    Extraction and antioxidant activities of polysaccharides from roots of Arctium lappa L

    Int. J. Biol. Macromol.

    (2019)
  • S.Y. Jin et al.

    Ethanol extracts of Panax notoginseng increase lifespan and protect against oxidative stress in Caenorhabditis elegans via the insulin/IGF-1 signaling pathway

    J. Funct. Foods

    (2019)
  • X.H. Kan et al.

    Evaluation of bioaccessibility of zeaxanthin dipalmitate from the fruits of Lycium barbarum in oil-in-water emulsions

    Food Hydrocoll.

    (2020)
  • X.M. Li

    Protective effect of Lycium barbarum polysaccharides on streptozotocin induced oxidative stress in rats

    Int. J. Biol. Macromol.

    (2007)
  • A. Masci et al.

    Lycium barbarum polysaccharides: extraction, purification, structural characterisation and evidence about hypoglycaemic and hypolipidaemic effects. A review

    Food Chem.

    (2018)
  • D. Nabarlatz et al.

    Purification of xylooligosaccharides from almond shells by ultrafiltration

    Sep. Purif. Technol.

    (2007)
  • T.C.S.P. Pires et al.

    Phenolic compounds profile, nutritional compounds and bioactive properties of Lycium barbarum L.: a comparative study with stems and fruits

    Ind. Crops Prod.

    (2018)
  • J.W. Sheng et al.

    Antioxidant properties of different molecular weight polysaccharides from Athyrium multidentatum (Doll.) Ching

    Carbohydr. Polym.

    (2014)
  • Y. Su et al.

    Structural characterization and antioxidant activity of polysaccharide from four auriculariales

    Carbohydr. Polym.

    (2020)
  • L.Q. Sun et al.

    Immunomodulation and antitumor activities of different-molecular-weight polysaccharides from Porphyridium cruentum

    Carbohydr. Polym.

    (2012)
  • Cited by (32)

    View all citing articles on Scopus
    View full text