Antioxidant, antiradical, and antimicrobial activities of polysaccharides obtained by microwave-assisted extraction method A review

Journal Pre-proofAntioxidant, antiradical, and antimicrobial activities of polysaccharides obtained by microwave-assisted extraction method: A review Monirsadat Mirzadeh, Mohammad Reza A

Journal Pre-proof

Antioxidant, antiradical, and antimicrobial activities of polysaccharides

obtained by microwave-assisted extraction method: A review

Monirsadat Mirzadeh, Mohammad Reza Arianejad, Leila Khedmat

DOI: https://doi.org/10.1016/j.carbpol.2019.115421

To appear in: Carbohydrate Polymers

Received Date: 8 August 2019

Revised Date: 22 September 2019

Accepted Date: 30 September 2019

Please cite this article as: Mirzadeh M, Arianejad MR, Khedmat L, Antioxidant, antiradical, and antimicrobial activities of polysaccharides obtained by microwave-assisted extraction method:

A review, Carbohydrate Polymers (2019), doi:https://doi.org/10.1016/j.carbpol.2019.115421

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© 2019 Published by Elsevier.

Antioxidant, antiradical, and antimicrobial activities of polysaccharides

obtained by microwave-assisted extraction method: A review

Monirsadat Mirzadeh1, Mohammad Reza Arianejad2, Leila Khedmat3, *

1 Metabolic Disease Research Center, Qazvin University of Medical Sciences, Qazvin, Iran

2Department of Food Science and Technology, Faculty of Nutrition, Tabriz University of Medical Sciences, Tabriz, Iran

3 Health Management Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran

*Corresponding author’s Email: lkhedmat@yahoo.com; Tel: +98-912-387-3622

Highlights

 Great bio-functionalities of polysaccharides extracted by microwave-assisted (MAE)

 The high capacity of polysaccharides to quench DPPH·, OH·, NO·, ABTS·+, and O2 ·−

 The dose-dependent reducing, chelating, and lipid peroxidation inhibition activities

 Uronic acids are the main constituents involved in the antioxidative properties

 Strong antibacterial, antifungal, and antiviral activities of MAE-polysaccharides

Abstract

The antioxidant and antimicrobial activities of polysaccharides extracted by microwave-assisted

extraction (MAE) were reviewed An ascending dose-dependent manner was found for the in

vitro antioxidant (e.g., nitrite scavenging, phospho-molybdenum reduction, inhibition of lipid

peroxidation (ILP), ferric reducing power, and ferrous metal ions chelating), and antiradical (against DPPH·, OH·, ABTS·, NO·, and O2·−) activities There was a positive and significant correlation between ILP and erythrocyte hemolysis inhibition, showing the excellent

antioxidative properties to prevent the risk of cell damage These carbohydrate-based polymers

in vivo could reduce malonaldehyde and protein carbonyls and increase stress-resistance-related

enzymes such as catalase, superoxide dismutase, and glutathioneperoxidase They showed an effective bactericidal activity against a wide variety of gram-negative and gram-positive bacterial

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infections The in vitro strong antifungal and antiviral activities of sulfated polysaccharides

extracted by MAE were also diagnosed without any cytotoxicity effect Therefore, these

biomacromolecules might be used to develop functional foods and nutraceuticals

Abbreviations

UAE: ultrasound-assisted extraction, MAE: microwave-assisted extraction, PWE: pressurized water extraction, SWE: subcritical water extraction, EAE: enzyme assistance extraction, HWE: hot-water extraction, SFE: supercritical fluid extraction, Mw: molecular weight, PMRA:

phospho-molybdenum reduction activity, ILP: inhibition of lipid peroxidation, FRAP: ferric reducing antioxidant power, FICA: ferrous ion chelating activity, RP: reducing power, ROSs: reactive oxygen species, AAPH: 2,2′‐Azobis(2‐amidinopropane) dihydrochloride, ORAC:

oxygen radical absorbance capacity, PCCs: positive control compounds, MVI: methyl viologen induction, HPI: hydrogen peroxide induction, MDA: malonaldehyde, SOD: superoxide

dismutase, PCO: protein carbonyls, CAT: catalase, GSH: glutathione, GSH-Px: glutathione peroxidase, NO: nitric oxide, iNOS: nitric oxide synthase, CYP: cyclophosphamide, ST: survival time, RBP: rice bran polysaccharide, MIC: minimum inhibitory concentration, RSM: response surface methodology

Keywords: Bioactive polysaccharide, Extraction, Microwave, Antioxidant, Antibacterial,

Disease prevention

1 Introduction

Polysaccharides are biopolymers consisting of a high number of monosaccharideslinked by glycosidic bonds These macromolecules have been utilized as non-toxic ingredients to design functional products in agriculture, health-food, cosmetics, and medical industries (Chen, Ji, Xu,

& Liu, 2019; Hu, Liu, et al., 2019) The various extraction methods are applied to extract

polysaccharides from natural sources such as plant and algae materials, and microorganisms The extraction technique plays a significant role in the yield, chemical structure, and bioactivity of carbohydrate-based polymers (Guo et al., 2019; Rostami & Gharibzahedi, 2017a, b) Therefore,

it is necessary to find an appropriate extraction method to maintain the physicochemical,

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rheological, functional, and structural properties of polysaccharides (Cheng, Feng, Jia, Li, Zhou,

& Ding, 2013; Gharibzahedi, Smith, & Guo, 2019a; Yuan, Xu, Jing, Zou, Zhang, & Li, 2018)

A hot reflux unit during a multiple-step process is applied to extract polysaccharides in the conventional method This traditional process under high temperatures usually leads to the low extraction rate of polysaccharides at extended times (Hu, Zhao, et al., 2019; Tahmouzi, 2014) However, the yield and bioactivity of polysaccharides can be promoted by some high-efficient techniques such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), pressurized water extraction (PWE), and enzyme assistance extraction (EAE) (Chen, Fang, Ran, Tan, Yu, & Kan, 2019; Gharibzahedi & Mohammadnabi, 2017; Li, Wang, Zhang, Huang, & Ma, 2011) MAE is an innovative extraction system to extract high-yield polysaccharides at a shorter time and lower solvent and energy consumption (Fig 1) This extraction method has higher extraction rate compared to the other technologies such as Soxhlet, PWE, and supercritical fluid extraction (SFE) owing to the rapid heating (Zeng, Zhang, Gao, Jia, & Chen, 2012) Also, MAE

as a sample preparation technique could be easily coupled with analytical systems such as

chromatography and spectroscopy to assess bioactive compounds (Xia, Wang, Xu, Zhu, Song, &

Li, 2011) The high ability of MAE in enhancing extraction yield is because of the molecular interactions between the electric component of the microwave field with the dipolar molecules and the ionic species present in the extraction mixtures (solvent-sample) This technology

through penetrating energy into solid materials in terms of nonionizing radiation in a spectral frequency of 300-300,000 MHz generates volumetrically-distributed heating because of the molecular friction (Rodriguez-Jasso, Mussatto, Pastrana, Aguilar, & Teixeira, 2011) This

mechanism originates from the dipolar rotation of polar solvents and the conductive migration of dissolved ions, enhancing the mass transfer coefficient of target ingredients (Pandit, Vijayanand,

& Kulkarni, 2015) Thus, the direct effect of microwaves on molecules through the simultaneous occurrence of dipole polarization and ionic conduction can change microwave energy into

thermal one, leading to an almost immediate heating up of the sample to extract bioactive

compounds within material matrix toward the solution MAE is thus considered as a promising technique for extracting polysaccharides with significant bioactivities (Bhatia, Sharma, Nagpal,

& Bera, 2015; Wang et al., 2018; Zhao, Zhang, & Zhou, 2019) The microwave irradiation with the deep rupture of the cell wall at short extraction times improves the yield and bioactivity of polysaccharides as a result of the effect of microwaves on both the solvent (volumetric heating)

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and the sample (improved liberate of polysaccharides from the matrix into the solvent) (Soria, Ruiz-Aceituno, Ramos, & Sanz, 2015) A number of structural factors such as monosaccharide composition, uronic acids content, molecular weight (Mw), glycosidic bond type in the backbone chain, and the esterification degree are profoundly affected on the antiradical, antioxidant, and antimicrobial activities of polysaccharides extracted from biological sources (Zhang, Lv, He, Shi, Pan, & Fan, 2013) The polysaccharides extracted by MAE show the excellent biological properties owing to the integrity of molecular structures in terms of functional glycosidic

linkages with a higher Mw, and uronic acid content

Despite the critical role of MAE as a novel technology in the extraction of bioactive

polysaccharides, there is still no review study about the effects of microwave waves in

improving the biological properties of these macromolecules With the current review, the aim was to present a comprehensive overview of the progress so far made regarding the application

of MAE and its principal operating parameters in improving biofunctional properties such as antioxidant, antiradical, and antibacterial, antifungal, and antiviral activities of polysaccharides from different sources

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Fig 1 A schematic representation of the MAE system for polysaccharides

2 In vitro antioxidant activity

2.1 Nitrite scavenging and phospho-molybdenum reduction activities

In the food industry, nitrite is one of the most common ingredients in meat processing to

intensify the color of final products and to extend their shelflife period However, the

pro-carcinogenic agent of nitrosamine can be generated via the chemical reaction between nitrite and amine constitutes present in protein-rich substances, medicines, and pesticide residues

Nitrosamine can be linked to diazoalkane, proteins, and intracellular components in the body and increased the cell damage and cancer risk (Lee, Kim, Jeong, & Park, 2006) Hence, it is

interesting to find the ingredients with protective functions through scavenging nitrosamine or its precursor, reducing the formation of cancer cells (Gharibzahedi, Razavi, & Mousavi, 2013; Javanbakht et al., 2017) A potent nitrite scavenging activity (NSA) was reported for

polysaccharides extracted from Fructus Meliae Toosendan (Xu, Yu, Wang, Xu, & Liu, 2018), and four seaweeds including Durvillaea antarctica, Gracilaria lemaneiformis, Sarcodia

ceylonensis, and Ulva lactuca (He, Xu, Chen, & Sun, 2016) using MAE A dose-dependent NSA

behavior for polysaccharides extracted from F Meliae Toosendan (1.2-2.0 mg/mL) and the

different seaweeds (1.0-4.0 mg/mL) was observed The maximum NSA value (67.3%) of F

Meliae Toosendan polysaccharide was found at the concentration of 2.0 mg/mL (Xu, Yu, et al.,

2018) The lowest (< 25%, at 1.0 mg/mL) and highest (~52%, %, at 4.0 mg/mL) NSAs among

seaweeds were for polysaccharides obtained from D antarctica and S ceylonensis, respectively

(He et al., 2016) Nevertheless, He et al (2016) reported that the effectiveness order of seaweed

polysaccharides to induce NSA as follow: S ceylonensis > U lactuca > D antarctica > G

lemaneiformis Besides, the NSA ability of seaweeds was weaker than their potential to quench

free radicals The high presence of sulfated groups in the structure of polysaccharides, especially

at more concentrations has an essential role in scavenging nitrite groups Also, the hydroxyl groups of polysaccharides can typically prevent the development of nitrosamines by donating hydrogens (Wang, Li, Zeng, & Liu, 2008; Zhang, Wang, Wang, Liu, Hou, & Zhang, 2010) On the other hand, Preethi and Mary Saral (2016) evaluated the phospho-molybdenum reduction activity (PMRA) of three polysaccharide fractions (PDP-1, PDP-2, and PDP-3) isolated from the

fruits of Pithecellobium dulce A concentration-dependent PMRA pattern was identified in the

range of 2-10 mg/mL They reported a high potential for the quantitative reduction of

molybdenum (VI) to molybdenum (V) (~68-75%) for the three fractions at 10 mg/mL

2.2 Inhibition of lipid peroxidation and erythrocyte hemolysis

The inhibition activities of polysaccharides obtained from the fruit bodies of Auricularia

auricular (Zeng et al., 2012) and fresh stems of Dendrobium devonianum (Li, Li, Peng, Xie,

Ruan, & Huang, 2018) on lipid peroxidation were assessed based on the thiobarbituric acid

method Zeng et al (2012) declared that the polysaccharide of A auricular in a dose-dependent

pattern could significantly increase the inhibition of lipid peroxidation (ILP) in egg yolk

homogenate The minimum (47.6%) and maximum (80.4%) values of ILP were recorded at concentrations of 0.0625 and 1.0 mg/mL, respectively The potential of ILP in this study was

more than that of polysaccharides obtained from A auricular by Fan, Zhang, Yu, and Ma (2007)

This discrepancy may be due to the difference in the extraction method (hot-water extraction (HWE) vs MAE) and Mw of extracted polysaccharides The lower Mw of polysaccharides obtained by MAE probably caused a significant increase in antioxidant activities because these biomolecules have a high number of free hydroxyl groups which can decrease the viscosity and increase the solubility of compounds (Zhang, Lv, Song, Jin, Huang, Fan, & Cai, 2015) The

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inhibition of FeCl2-induced lipid peroxidation by the polysaccharides extracted from nonpuffed

(44.5%) and puffed (47.6%) strips of D devonianum (particularly in higher concentrations, 2.0

mg/mL) may be due to the high number of hydroxyl groups (Li et al., 2018) The erythrocyte membrane composes of polyunsaturated fatty acids susceptible to free radical-induced

peroxidation The presence of bioactive polysaccharides due to the high number of uronic acidscontaining both hydroxyl and carboxylic acid functional groups can quench free radicals,

preventing the hemolysis of blood cells (Cheng et al., 2013) Fernandes, Filipe, Coelho, and Manso (1991) earlier mentioned that the ILP was accompanied by the inhibition of hemolysis in red-cells For the first time, Cheng et al (2013) evaluated the erythrocyte hemolysis inhibition

(EHI) activity of polysaccharides (Epimedium acuminatum) extracted by MAE on blood samples

collected from a healthy volunteer The hemolysis was induced by

2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH), which is a known model to assess the oxidative damage of cells membrane They pointed out that the polysaccharide fractions (EAP- (E, H, M,

U)) from E acuminatum had a protective effect through the hemolysis inhibition of human red

blood cells This antioxidant capacity decreases the formation of free radicals mediated by

AAPH, which may be attributed to the reduction of oxidative injury of biological membranes (Ma, Liu, Zhou, Yang, & Liu, 2000)

2.3 Reducing power of ferric ions

The ferric reducing antioxidant power (FRAP) of polysaccharides obtained from E acuminatum

(Cheng et al 2013), paddlefish cartilage (Zhang, Zhao, Xiong, Huang, & Shen, 2013), tangerine peels (Chen, Jin, Tong, Lu, Tan, Tian, & Chang, 2016), bamboo leaves (Zhang, Li, Zhong, Peng,

& Sun, 2016), and okra (Yuan et al., 2019) by MAE method was evaluated A dependent manner was found for the reducing colorless Fe(III) to colored Fe(II)-

concentration-tripyridyltriazine form according to the absorbance measured at 593 nm An increase in

concentration of polysaccharides of E acuminatum (0-1.0 mg/mL), tangerine peels and bamboo

leaves (0-5.0 mg/mL), and okra (0.5-4.5 mg/mL) could significantly improve the FRAP The okra polysaccharide extracted by MAE had a higher FRAP compared to that obtained by HWE and PWE at all the used concentrations was found (Yuan et al., 2019) It seems that these

electron-donating antioxidant components because of the presence of a high number of uronic acids in their structure are able to reduce ferric ions Furthermore, the use of microwave radiation

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reduces the MW of extracted polysaccharides through changing the structural configuration by loosening the matrix of the cell wall and separating the parenchyma cells and thus enhances the extraction yield and antioxidant activity (Kaufmann & Christen, 2002)

In the reducing power (RP) assay, the presence of antioxidant polysaccharides reduces the

Fe(III)/ferricyanide complex to the form of Fe(II) As a result, the level of Fe(II) in antioxidant solutions can be checked by determining the formation of Prussian blue at 700 nm In recent years, numerous studies have been assessed the reducing power of polysaccharides extracted by MAE (Table 1)

The hydrogen-donating ability through active hydroxyl and carboxyl groups present in the

molecular enables polysaccharides to reduce Fe(III)/ferricyanide ions This antioxidant capacity also acts through breaking the free-radical chain and preventing the peroxide formation via the reaction with specific precursors of peroxide (Esfehani, Ghasemzadeh, & Mirzadeh, 2018;

Gharibzahedi, 2017; Wang, Zhang, Wang, Zhao, Wu, & Yao, 2009; Wang, Zhang, Zhao, Wang, X., Wu, & Yao, 2010; Zhang, Lv, et al., 2013) Yuan and Macquarrie (2015), and He et al (2016) showed that the sulfation could highly improve the RP of polysaccharides extracted from

seaweeds of Ascophyllum nodosum, S ceylonensis, G lemaneiformis, D antarctica, and U

lactuca In general, there was a dose-dependent manner in RP of polysaccharides so that the

highest used concentration showed the maximum RP

However, the difference in RP of different polysaccharides can be due to the discrepancy in their degree of substitutions, Mw, monosaccharide composition, and glycosidic linkages (Wang, Hu, Nie, Yu, & Xie, 2016) Among all the studied carbohydrate polymers, polysaccharides extracted

from Gentiana scabra bge (Cheng, Zhang, Song, Zhou, Zhong, Hu, & Feng, 2016) at 1.2 mg/mL,

Lilium davidii var unicolor Salisb (Zhao, Zhang, Guo, & Wang, 2013) at 4.0 mg/mL, Chuanminshen violaceum (Dong, Zhang, et al., 2016) at 4.0 mg/mL, and A auricular and Panax ginseng (Zeng et al., 2012; Zhao et al., 2019) at 10 mg/mL exhibited the most potent RP Therefore,

these biomacromolecules are high-potential photochemical ingredients to be formulated in potent therapeutic drugs and care products in modern medicine Yuan and Macquarrie (2015) evaluated the MAE times (5, 15, and 30 min) and temperatures (90, 120, and 150°C) on the RP of fucoidan

extracted from A nodosum They proved that the RP of fucoidan increases with a decrease in MAE

temperature due to the more sulfate content (Hu, Liu, Chen, Wu, & Wang, 2010; Yang, Liu, Wu,

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Chen, & Wang, 2011) Besides, 15 min was considered an optimal time to extract fucoidan using MAE method (Yuan & Macquarrie, 2015)

Table 1 A summary of dose-dependent reducing power of polysaccharides extracted by MAE

Polysaccharide source Concentration (mg/mL) a Maximum RP (Ǻ700 nm) Reference

Agaricus blazei Murrill 0.2-2.0 ~0.85-0.90 Zhang, Lv, Pan, Shi, and Fan (2011)

a The best dose detected to show the reducing power was the upper limit of the selected concentration range.

2.4 Ferrous metal ions chelating activity

A dose-dependent manner in the ferrous ion chelating activity (FICA) was found for

polysaccharides extracted from Artemisia sphaerocephala (Wang et al., 2009), Potentilla

anserina (Wang et al., 2010), himematsutake (Zhang, Lv, Pan, Shi, & Fan, 2011), Flammulina

velutipes (Zhang, Lv, et al., 2013), L davidii var unicolor Salisb (Zhao et al., 2013), Poria cocos

Wolf (Wang, Zhang, et al., 2016), Dendrobium officinale (He et al., 2018), bamboo shoots

(Chen, Fang, et al., 2019), seabuckthorn (Wei et al., 2019), and Chlorella vulgaris (Yu et al.,

2019) by MAE It was demonstrated that the delay in the metal-catalyzed oxidation could be

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improved with increasing the polysaccharide concentration Although the FICA of these

biomacromolecules was desirable, this antioxidant index in most polysaccharides was

determined to be lower than EDTA Naughton and Grootveld (2001) explained that the FICA of EDTA is due to the presence of functional groups containing nitrogen and carboxyl However, the FICA of polysaccharides may also be ascribed to the hydroxyl groups and the formation of cross-bridge between carboxyl groups in the structure of uronic acids and divalent ions of iron (Wang et al., 2009; Yu et al., 2019)

Accordingly, Wei et al (2019) mentioned that the increase of microwave power by 650 W could significantly reduce the FICA of polysaccharides extracted from seabuckthorn berries with an enhancement in the cleavage rate of glucosidic bonds and a decrease in the number of hydroxyl

groups Generally, the FICAs of A sphaerocephala and Chimonobambusa quadrangularis

polysaccharides obtained by MAE were higher than those of the same polysaccharides extracted

by HWE (Chen, Fang, et al., 2019; Wang et al., 2009) This fact may be owing to the microwave heating, causing polarization of polar bonds (like the C-O-C glycosidic linkage) and the enhancement of molecular reactivity (Zhang, Lv, et al., 2013) The chelating ability of Fe(II) ions

by chelators through forming σ bonds is an essential biological defense mechanism because this function can remove Fe(II) ions participating in hydroxyl radical-generating Fenton-type reactions The cell protection against oxidative damages thus can be possible by minimizing Fe(II) ions and inhibiting the formation of reactive oxygen species (ROSs) and lipid peroxidation (Gharibzahedi, 2018; Zhang, Lv, et al., 2013)

3 In vitro antiradical activity

3.1 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging activity

DPPH· is a stable nitrogen-centered on free radical with an unpaired electron which is

responsible for the strong absorbance at 517 nm The number of this free radical can easily decrease in the exposure to proton radical scavengers The deep-purple solution of DPPH· can be changed to yellow as it is quenched by antioxidants (Sharma & Bhat, 2009) DPPH· was the most common free radical used to determine antiradical and antioxidant activities of

polysaccharides extracted by MAE (Table 2) The maximum DPPH· radical scavenging

percentage of an infinite number of polysaccharides extracted under the optimum conditions accompanied by their monosaccharide composition and MW is given in Table 2 According to

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the tested concentrations, the most potent polysaccharides extracted by MAE to quench DPPH·

radical were obtained from E acuminatum (~92%, at 0.004 mg/mL), okra pods (67.0%, at 0.018 mg/mL), Palmaria palmata (51.32%, at 0.025 mg/mL), Hippophae rhamnoides L (55%, at 0.05 mg/mL), Sargassum thunbergii (90.8-95.2%, at 0.4 mg/mL), Opuntia ficus indica (82.0%, at 0.4 mg/mL), Zizyphus jujuba Mill (67.0-74.1%, at 0.2 mg/mL), C vulgaris (65.1%, at 0.4 mg/mL),

and mung bean hulls (83.2%, at 0.8 mg/mL) (Table 2) As a result, these biomacromolecules could be employed as a potential antioxidative and nutraceutical ingredient in designing

functional foods, medicinal products, and pharmaceutical formulations (Izadi, Khedmat, & Mojtahedi, 2019; Xiong, Li, Zheng, Hu, Cui, & Li, 2019) Similar to the other antioxidant

assessments, a concentration-dependent behavior was observed to scavenge DPPH· The

presence of electrophilic groups (like keto or aldehyde) in acidic polysaccharides can improve the DPPH· scavenging ability through facilitating the hydrogen release from O–H bond Hence, the enhanced hydrogen-donating ability at high polysaccharide concentrations is related to the high number of unmethylated uronic acids and hydroxyl groups (Song, Chen, Li, Jia, & Zhong, 2018; Yin, Fan, Fan, Shi, & Gao, 2018) Maintaining the triple helical structure integrity in extracted polysaccharides with lower MWs also can significantly intensify their potential to scavenge DPPH· Under this condition, smaller polysaccharide fractions due to their larger surface area have a greater chance to contact with the different types of radicals such as DPPH· (Chen, Fang, et al., 2019) Chen, Xu, and Zhu (2010) also explained that the low ratio of glucose

in the glycosidic structure might represent better antioxidant ability

3.2 Hydroxyl (OH·) radical scavenging activity

Since the highly active OH· radical can quickly react with any biomolecules, it may cause severe damages to the adjacent tissues or organs Hence, finding the biomaterials with removal ability

of OH· radical is necessary for antioxidant defense in cell systems Table 2 shows the highest OH· scavenging activity of polysaccharides extracted by MAE at the optimal concentration At the high concentration of 10 mg/mL, the maximum OH· inhibition rate for polysaccharides

extracted from A sphaerocephala, P anserina, Lycium ruthenicum, and A auricular was 50.1,

50.1, ~68, and ~95%, respectively (Table 2) However, some polysaccharides extracted by MAE

exhibited a considerable OH· scavenging activity at very low doses, including H rhamnoides at 0.08 mg/kg (~90%), Carex meyeriana Kunth at 0.2 mg/kg (~75%), C vulgaris at 0.4 mg/kg

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(56.2%), and S thunbergii at 0.8 mg/kg (68.7-72.4%) (Table 2) Two mechanisms involved in

this antioxidant activity are the generation suppression of OH· and the cleaning of formed

radicals (Qu, Yu, Jin, Wang, & Luo, 2013; Wang et al., 2009) In general, an increase in the concentration of polysaccharides extracted by MAE could significantly improve the inhibition rate of OH· radical The addition of electron-donating substituent enhanced the inhibition rate of OH· owing to the increased electron density on the heterocyclic ring of the carbons (Jeong, Seo,

& Jeong, 2009) Therefore, the more hydrogen donation to OH· radicals by crude and purified polysaccharides can produce stable radicals to block the chain reaction This antiradical activity

is highly associated with the iron-chelating ability of polysaccharides (Wang et al., 2010; Wei et al., 2019) This radical type plays a significant role in superoxidation by H2O2 with metal ions (e.g., ferrous or copper) Accordingly, polysaccharides with metal chelating capacity render them inactive in Fenton reaction may have a high ability to inhibit OH· radical (Zhang, Lv, et al., 2013) He et al (2018) have recently evaluated the H2O2 scavenging potential of polysaccharides

extracted from D officinale stem by MAE They found that the use of 5 mg/mL of this

biopolymer could notably improve the H2O2 scavenging activity (> 80%) Instead, the low

activity in scavenging OH· by some polysaccharides probably is because of the formation of strong intermolecular and intramolecular hydrogen bonds, leading to the reactivity inhibition of hydroxyl groups in the polymer chains (Cheng et al., 2016; Jeong et al., 2009)

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Table 2 The DPPH· and OH· radical scavenging activities of different polysaccharides extracted under the optimal MAE conditions

Polysaccharide

source

Yield (%)

Optimal MAE conditions a

Monosaccharide composition (molar ratio, or %) b

MW (Da)

Maximum DPPH· scavenging activity (at an optimal dose)

Maximum OH· scavenging activity (at an optimal dose)

49.14×10 5

0.3751-52.32% (at 2.0 mg/mL) 50.1% (at 10.0 mg/mL) Wang et al

15.1×10 3 92.5% (at 2.0 mg/mL) ~100% (at 1.0 mg/mL) Wang,

Zhang, et al (2016) Okra pods 14.79 S/M, 5:1; MP, 395.56

W; E Te , 73.33°C; E Ti , 67.11 min

2.77×10 4 75.4% (at 10.0 mg/mL) ~95% (at 10.0 mg/mL) Zeng et al

(2012) Bamboo shoots 9.94 S/M, 20:1; MP, 400 W;

E Te , 90°C; E Ti , 15 min

Man (1.85%), Rha (0.88%), Glc (33.81%), Gal (20.89%), Xyl (15.22%) Ara (20.48%), GlcA (1.17%), GalA (5.7%)

13.607×10 4 ~68% (at 4.0 mg/mL) ~72% (at 4.0 mg/mL) Chen, Fang,

et al (2019)

Chuanminshen

violaceum

34.59 S/M, 40:1; MP, 450 W;

ETe, 65°C; ETi, 15 min

Ara (2.25%), Xyl (4.26%), Man (7.41%), Gal (38.62%), Glc

(47.15%)

2.11×10 3 4.06×10 5

ND 64.34% (at 2.5 mg/mL) 33.40% (at 2.5 mg/mL) Zhang, Lv, et

Li, Yi, and Huang (2019) Mung bean hulls 60.03 d S/M: 17:1; 700 W; E Ti ,

(2019) Journal Pre-proof

Table 2 Continued

Polysaccharide

source

Yield (%)

Optimal MAE conditions a

Monosaccharide composition (molar ratio, or %) b

MW (Da) Maximum DPPH· scavenging

activity (at an optimal dose)

Maximum OH· scavenging activity (at an optimal dose)

(2019)

viper’s bugloss 25.11 S/M, 61.4:1; MP, 769.2

W; E Te , 42.3°C; E Ti , 73.8 min

Ara (2.56%), Xyl 3.78%), Man (4.19-6.25%), Gal (40.58-49.45%), Glc (43.55-46.83%)

(2.81- 11.02×10 3

Zhang, et al (2016)

(48.88-4.51×10 3 - 2.08×10 5 M *

68.23% (at 4.0 mg/mL) ~35% (at 4.0 mg/mL) Wang et al

37.54×10 3

Macquarrie (2015)

Ulva prolifera 36.38 S/M, 20:1; 0.01 M

HCl, MF, 2.45 GHz;

MP, 500 W; E Te , 120°C, E Ti , 15 min

Man (0.04-1.05%), Rha 42.17%), GlcA (2.58-22.77%), GalA (0.24-0.91%), Glc (24.37-87.22%), Gal (0.10- 1.90%), Xyl (0.58-7.54%), Ara

(9.29-(0.16-0.93%)

227×10 3

Table 2 Continued

Polysaccharide

source

Yield (%)

Optimal MAE conditions a

Monosaccharide composition (molar ratio, or %) b

MW (Da) Maximum DPPH· scavenging

activity (at an optimal dose)

Maximum OH· scavenging activity (at an optimal dose)

E Ti , 19.55 min; S/M, 50:1

Man (8.22,10.46%), Rib (1.33,10.31%), GlcA (1.14%), Glc (71.26,72.50%), Gal (3.44,12.71%), Ara (0.52,4.54%), Fuc (3.60%)

3.9×10 3 11.95×10 4

-38.7, 43.9% (at 2.0 mg/mL) 74.4, 82.1% (at 2.0 mg/mL) Lin et al (2019)

Zizyphus jujuba 9.02 S/M, 30:1; MP, 400 W;

E Te , 75°C, E Ti , 60 min

Glc (1.2-1.4), Ara (1.8-2.1), Gal (4.1-4.2), Rha (0.9-1.1)

9.1×10 4 1.5×10 5

Gharibzahedi (2016)

Phyllostachys

acuta

1993 mg/L *

S/M, 15:1; E Te , 70°C,

E Ti , 40 min

mg/g: Man (6.9-14.6), Fuc (7.8-13.0), Xyl (40.9-109.0), Glc (167-246.7), Gal (167.0- 289.2), Ara (258.0-414.6)

D-3.3×10 3 96.83×10 4

-~55% (at 0.05 mg/mL) ~90% (at 0.05 mg/mL) Wei et al (2019)

E Te , 52.2°C, E Ti , 41.8

min

GalA (42.5%), Ara (23.0%), Gal (20.0%), Rha (6.9%), Glc (4.2%), Man (3.5%)

17.8×10 3 82.5% (at 2.0 mg/mL) 95.7% (at 4.0 mg/mL) Chen et al (2016)

(23.2-190.4×10 3 90.80-95.23% (at 0.4 mg/mL) 68.7-72.4% (at 0.8 mg/mL) Ren, Chen, Li, Fu,

You, and Liu (2017)

Table 2 Continued

Polysaccharide

source

Yield (%)

Optimal MAE conditions a

Monosaccharide composition (molar ratio, or %) b

MW (Da) Maximum DPPH· scavenging

activity (at an optimal dose)

Maximum OH· scavenging activity (at an optimal dose)

-12.055×10 3 , 38.83×10 3

(2.4%)

Emam-Djomeh, Askari, and Fathi (2019) Birch (lignin) 26.49 S/M, 10:1; MP, 700

W; E Te , 101°C, E Ti ,

30 min

7.29-10.86×10 3 M *

Wang, Xu, and Sun (2012)

Ficus carica 9.62 S/M, 15:1; MP, 600

W; E Ti , 3.5 min; pH,

1.4

GlcA (0.3), GalA (3.3), Glc (0.8), Fuc (0.5), Ara (0.3), Gal (1.0), Rha (0.2), Man (0.1)

1.1-4.29×10 3 65.1% (at 0.4 mg/mL) 56.2% (at 0.4 mg/mL) Yu et al (2019)

F velutipes ND S/M, 20:1; MP, 650

W; E Te , 50°C, E Ti , 2 min

Glc (4.24-24.17), Gal 13.98), Man (1.82-3.67), Xyl

(2.05-(1.0)

62.29×10 3

29.93-47.38-65.34% (at 8.0 mg/mL) 85.41-88.21% (at 8.0 mg/mL) Liu, Zhang,

Ibrahim, Gao, Yang, and Huang (2016)

a S/M: solvent: material (v/w), MP: microwave power (W), E Te : Extraction temperature (°C), E Ti : Extraction time (min), MF: Microwave frequency (MHz)

b Ara: arabinose, Xyl: xylose, Lyx: lyxose, Man: mannose, Glc: glucose, Gal: galactose, Rha: rhamnose, GlcA: glucuronic acid, GalA: galacturonic acid, Fuc,

fucose, Fru: fructose, Rib: ribose, Lac: lactose; cND: not detected; d Based on mg glucose equivalent (GE)/g dry weight (DW)

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3.3 ABTS radical scavenging activity

ABTS· (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) is a nitrogen-centered synthetic radical cation which is produced through oxidizing ABTS with potassium persulphate An

antioxidant component can convert ABTS· to its non-radical form by donating an electron This antioxidant assay can be measured according to the reduction of the blue-green solution

containing ABTS· radical cation at 734 nm

In recent years, the polysaccharides extracted from natural sources by MAE demonstrated the considerable ABTS radical scavenging activities (Fig 2) Some of these algal and plant sources

were A auricular (IC50 = 1.23 mg/mL; Zeng et al., 2012), E acuminatum (36.63% at 2.0

mg/mL; Chen et al., 2013), Berberis dasystachya Maxim (77.09% at 12 mg/mL; Han, Suo, Yang, Meng, & Hu, 2016), seaweeds of S ceylonensis, U lactuca L., and D antarctica (IC50 =

3.59-3.99 mg/mL; He et al., 2016), C violaceum (95.29% at 2.0 mg/mL; Dong, Lin, et al.,

2016), C violaceum (98.82-100% at 10.0 mg/mL; Dong, Zhang, et al., 2016), F velutipes

(97.03-98.92% at 6.0 mg/mL; Liu, Zhang, Ibrahim, Gao, Yang, & Huang, 2016), C meyeriana

Kunth (IC50 = 0.0399 mg/kg; Hu et al., 2018), D officinale (IC50 = 2.659 mg/mL; He et al.,

2018), U prolifera (68.6% at 2.0 mg/mL; Yuan et al 2018), C quadrangularis (IC50 = 0.582 mg/mL; Chen, Fang, et al., 2019), common fig (~ 75% at 15 mg/mL; Gharibzahedi et al., 2019a), snow chrysanthemum (IC50 ≤ 1.121 mg/mL; Guo et al., 2019), kiwifruit (~72% at 3.0 mg/mL;

Han et al., 2019), U pertusa (50.37% at 0.8 mg/mL; Le et al., 2019), okra (IC50 = 2.50-4.40

mg/mL; Yuan et al., 2019), and P ginseng (97.09% at 10.0 mg/mL; Zhao et al 2019) Results showed that the polysaccharides extracted from U prolifera and C meyeriana Kunth had

substantial scavenging capacity against ABTS radical (Fig 2a and 2b)

The radical scavenging of ABTS· by polysaccharides in most studies was lower than the positive control compounds (PCCs (e.g., vitamin C and BHA)) But it was reported that the

polysaccharide fractions extracted from C violaceum, F velutipes, and P ginseng had an equal

power or even more compared to vitamin C to scavenge ABTS· radical (Dong, Zhang, et al 2016; Liu et al., 2016; Zhao et al., 2019) This result might be attributable to the ABTS· radical being more suitable for determining hydrophilic antioxidant compounds compared to the other free radicals like DPPH (Floegel, Kim, Chung, Koo, & Chun, 2011; Gharibzahedi et al., 2013) Optimizing the MAE conditions could prevent the production of polysaccharides with a high denaturation rate or weak structural integrity (Gharibzahedi, Smith, & Guo, 2019b) Yuan et al

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(2018) found that the high sulfur content in the structure of U prolifera polysaccharides

compared to the low MW had a more pronounced role in improving the ABTS· radical

scavenging activity The presence of keto or aldehyde groups,high content of uronic acids, and plentiful monosaccharide components may increase the inhibition activities of ABTS· radical by acidic polysaccharides (Hu et al., 2018; Song et al., 2018)