Next Article in Journal
Halloysite Nanotube-Ferrihydrite Incorporated Polyethersulfone Mixed Matrix Membrane: Effect of Nanocomposite Loading on the Antifouling Performance
Next Article in Special Issue
In Vivo Characterization and Application of the PHA Synthase from Azotobacter vinelandii for the Biosynthesis of Polyhydroxyalkanoate Containing 4-Hydroxybutyrate
Previous Article in Journal
An Extended Thickness-Dependent Moisture Absorption Model for Unidirectional Carbon/Epoxy Composites
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Polymers
Volume 13
Issue 3
10.3390/polym13030442
polymers-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Antioxidant Potential of Physicochemically Characterized Gracilaria blodgettii Sulfated Polysaccharides

by
Bilal Muhammad Khan
1,2,3,†,
Li-Xin Zheng
1,†,
Wajid Khan
4,
Aftab Ali Shah
5,
Yang Liu
1 and
Kit-Leong Cheong
1,*
1
Guangdong Provincial Key Laboratory of Marine Biotechnology, STU-UNIVPM Joint Algal Research Center, Department of Biology, College of Science, Shantou University, Shantou 515063, China
2
University Institute of Biochemistry and Biotechnology, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi 46300, Punjab, Pakistan
3
National Center of Industrial Biotechnology, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi 46300, Punjab, Pakistan
4
Center for Biotechnology and Microbiology, University of Swat, Mingora 19130, Khyber Pakhtunkhwa, Pakistan
5
Department of Biotechnology, Faculty of Biological Sciences, University of Malakand, Chakdara, Lower Dir 18800, Khyber Pakhtunkhwa, Pakistan
*
Author to whom correspondence should be addressed.
†
These authors contribute equally to this manuscript.
Polymers 2021, 13(3), 442; https://doi.org/10.3390/polym13030442
Submission received: 30 December 2020 / Revised: 26 January 2021 / Accepted: 27 January 2021 / Published: 30 January 2021
(This article belongs to the Special Issue Biobased and Natural Polymers)
Browse Figures
Review Reports Versions Notes

Abstract

:
Marine rhodophyte polysaccharides have a wide range of described biological properties with nontoxic characteristics, and show great potential in prebiotics and the functional foods industries. However, there is a virtual lack of Gracilaria blodgettii polysaccharides (GBP) profiling and their bioactivities. This study was designed while keeping in view the lack of physical and chemical characterization of GBP. This polysaccharide was also not previously tested for any bioactivities. A linear random coil conformation was observed for GBP, which was found to be a polysaccharide. A significant sulfate (w/w, 9.16%) and 3,6-anhydrogalactose (AHG, w/w, 17.97%) content was found in GBP. The significant difference in its setting (27.33 °C) and melting (64.33 °C) points makes it resistant to increasing heat. This, in turn, points to its utility in industrial scale processing and in enhancing the shelf-life of products under high temperatures. A radical scavenging activity of 19.80%, 25.42% and 8.80% was noted for GBP (3 mg/mL) in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2’-azino-bis (ABTS) and hydroxyl radical (HO) scavenging assays, respectively. Therefore, the findings suggest that Gracilaria blodgettii polysaccharides display a good antioxidant potential and may have potential applications in the functional food industry.

1. Introduction

Covering the majority of the earth’s surface, oceans are inhabited by one of the most abundant, diverse and nutritionally important group of organisms [1]. As one of the most abundant organisms, algae has aroused an increasing interest in consumption all around the world, being used in the food, cosmetic or pharmaceutical industries [2,3,4]. Over the past 20 years, the global market of seaweed consumption has grown by about 20% [5]. Based on the different colors of thalli, algae are classified into three types: Rhodophyceae (red algae), Phaeophyceae (brown algae) and Chlorophyceae (green algae) [6]. Marine Rhodophytes contain distinctive polysaccharides, which are predominantly agarans or carrageenans [7]. In recent years, polysaccharides extracted from marine algae have been reported to exhibit various biological activities such as antioxidant, anticoagulant, antitumor, anti-inflammatory and immunomodulatory effects [8,9,10]. They have a wide range of health benefits for humans, including anti-aging, anti-breast cancer, gastroprotective and neuroprotection effects [8]. Thus, they became more and more important in biochemical and medical areas, also having received increasing attention in the past decade [11].
Rhodophytal polysaccharides’ backbone consists of a repetitive 3-linked β-D-galactopyranose and 4-linked α-galactopyranose disaccharide unit [12]. The carrageenan and agar of red algae are mainly composed of galactans [13,14]. Their α-galactose residues, on the other hand, are either primarily or entirely comprised of 3,6-anhydrogalactose [15].
Red algae, the profuse and primordial marine macrophytes [16], comprises one of the largest phyla of algae. It belongs to the genus Gracilaria, and it evidently shows its importance in the form of agrophytes by abundantly occupying vegetable market shelves as salad and serves as an imperative ingredient in the production of nonalcoholic drinks and certain foods [17]. It can grow and reproduce in a vast habitat extending from the Arctic Ocean to the Northern Hemisphere’s tropical seas, where Southeast Asia is located [18]. Given its easy accessibility, the genus Gracilaria is important to industries as the main source of agar, and it is also consumed locally as an everyday food with great demand [17]. In addition, it also has the potential to be used in the manufacturing of functional foods and nutraceuticals [19,20], which is a vibrant revenue-making industrial segment [21].
Reactive oxygen species (ROS) can be manifested in the form of apoptosis, cardiovascular disease and even cancer. Meanwhile, antioxidants combat the harmful effects of ROS, like the degenerative or pathological processes of various serious diseases such as inflammation, cardiac and neurological conditions, and nucleic acid, protein and lipid deformations [22,23,24]. The antioxidant potency of various seaweed-extracted sulfated polysaccharides has been previously reported. For instance, Patel reported that the sulfated polysaccharide extracted from red algae exhibited strong antioxidant, viz. carrageenans [25], while Bhadja et al. also found that polysaccharides with a high sulfate content significantly increased their antioxidant activity [8]. Furthermore, Torres et al. also reported that antioxidant activity is one of the most evaluated properties of the genus Gracilaria [26]. In general, the biological activities of SP are strongly related to their chemical structure, such as the content of sulfate groups and uronic acid, as well as its molecular weight [27]. Gracilaria blodgettii, however, virtually lacks specific polysaccharide profiling and bioactivities. Therefore, the evaluation and comparison of the polysaccharides of Gracilaria blodgettii, considering their chemical composition and bioactivities, were particularly necessary to broaden their applications in functional foods industry. The aim of the present study was to emphasize the physical and chemical characterization of Gracilaria blodgettii polysaccharides (GBP) and their potential utility as antioxidants. Our results may help to display potential applications in the functional food industry and might be useful for further biochemical studies in the future.

2. Materials and Methods

2.1. Plant Material and Reagents

After collecting G. blodgettii (Hainan Island, China) in December 2017, it was dried under vacuum conditions. The dried samples were ground into fine powder by a powder machine and sifted through an 80-mesh sieve. Aladdin (Shanghai China) provided Trifluoroacetic acid (TFA), acetonitrile and salicylate, while Sigma-Aldrich (St. Louis, MO, USA) delivered L-Ascorbic acid, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2’-azino-bis (ABTS) and 4-methyl-morpholine borane (MMB). Acetic anhydride, ethyl acetate and dichloromethane were procured from XiLong Scientific Co., China, and 3,6-anhydrogalactose (AHG) was procured from J&K Scientific Ltd., Beijing, China.

2.2. Polysaccharide Extraction

The removal of low molecular weight impurities was achieved by treating powdered material (25 g) with methanol/dichloromethane/water (4:2:1, v/v/v, 250 mL), and afterwards subjecting the resultant mixture to shaking incubation for 24 h at ambient temperature. This was followed by centrifugation (4000× g, 15 min) and the subsequent drying of the precipitate at 60 °C. The dried precipitate was resuspended in deionized distilled water (1:30, w/v), kept for 30 min at room temperature, and was then heat-treated in a water bath (90 °C) for 2 h. Following another round of centrifugation (4000× g, 15 min), 95% ethanol (three-fold) was added to the precipitate. The precipitate that was dissolved in ethanol was stored overnight at 4 °C before undergoing yet another round of centrifugation (4000× g, 15 min). The precipitate hence obtained was dissolved in hot water prior to freeze-drying for 24 h.

2.3. GBP Characterization

2.3.1. Sulfate Content

A modified BaCl2-gelatin turbidimetric technique [28] was used for the sulfate content determination. In a capped vial, the polysaccharide weighing 5 mg was hydrolyzed with 1 mol/L HCl (2.5 mL) for 3 h at 100 °C. The hydrolysate was allowed to cool down and was then diluted to a final volume of 50 mL with 1 mol/L HCl. Afterwards, it was filtered and trichloroacetic acid (TCA) was added (3%; v/v; 3.8 mL), together with BaCl2-gelatin solution (1 mL). The uniformity of the solution was ensured through vigorous mixing. A settling time of 15 min was given at room temperature. It was followed by a measurement of the absorbance at 360 nm for this solution (A1) and a solution of GBP/gelatin/TCA (A2). Subsequently, the value of A2 was subtracted from the value obtained for A1, which gave us the final absorbance (GBPabs). The standard curve was generated using a solution of K2SO4.

2.3.2. Total Sugar Content

The total sugar content of GBP was determined using the phenol-sulfuric acid method, where 200 μL of phenol solution (5%; w/v) and 1 mL of concentrated sulfuric acid was added to 200 μL of both the sample (2.5 mg/mL) and the standard glucose (0.2, 0.4, 0.6, 0.8 and 1 mg/mL). The mixtures, after vigorous shaking, were placed for 15 min in a boiling water bath and were then allowed to cool down. The measurement of the absorbance for the mixtures was carried out (490 nm) and was compared to the standard curve generated with glucose.

2.3.3. Setting/Melting Points Determination

A thermometer was inserted into a test tube containing 1.5% GBP solution (8 mL) in order to determine its setting point. The test tube was placed in an ice bath to lower the temperature. The temperature at which the GBP solution stopped flowing even after tilting the test tube at an angle of 90 °C was recorded as the setting point. The melting point, on the other hand, was determined by placing a small metal ball on the surface of the solidified GBP solution. The GBP solution was transferred to a water bath, and the temperature was gradually increased. That temperature was noted as the melting point at which the metal ball touched the bottom of the test tube.

2.3.4. High-Performance Size-Exclusion Chromatography

The weight-average molecular weight (Mw), number-average molecular weight (Mn), polydispersity (Mw /Mn), PD, intrinsic viscosity [η], hydrodynamic radius (Rh) and radius of gyration (Rg) of GBP were determined using a high-performance size-exclusion chromatography with multiple detectors, a viscometer, a refractive index detector and multi-angle laser light scattering (HPSEC-Visc-MALLS-RID). An Agilent 1100 series LC/DAD (Liquid chromatography coupled to diode array detector) system connected with a PL aquagel-OH MIXED-H column (300 mm × 7.8 mm) was used. A 30 °C column temperature was maintained. The determination of [η] for GBP followed the classic Huggins–Kraemer equations. RID was calibrated using a series of aqueous NaCl solutions of known concentrations. The mobile phase, 0.1 mol/L NaNO3 aqueous solution, had a flow rate of 0.5 mL/min. All samples were analyzed in a fixed injection volume (50 μL). ASTRA 5.0 software (Wyatt Technology Co., Goleta, CA, USA) was employed for data collection and analyses.

2.3.5. Reductive Hydrolysis and Acetylation

GCP was exposed to a twostep reductive hydrolysis with 4-methyl-morpholine borane (MMB) and trifluoroacetic acid (TFA), and afterwards to acetylation with ethyl acetate in accordance with a published protocol [29]. A Gas Chromatography-Mass Spectrometer (GC–MS) apparatus having an Rtx-5MS column (30 m × 0.2 mm × 0.25 µm) was used for AHG quantification in GBP. The injector temperature was fixed at 280 °C preceding the injection of the samples (1 μL with a split ratio of 1:10). The detector temperature was retained at 250 °C. The oven temperature regime was 60 °C (2 min) with an incremental rise of 30 °C/min up to 120 °C (1 min hold), and afterwards of 25 °C/min up to 250 °C (30 min hold). The carrier gas, N2, had a flow rate of 2 mL/min. Mass spectrometry was executed at 70 eV and 50–800 m/z scan fragments. The calibration curve for the quantification was obtained with standard AHG.

2.3.6. Scanning Electron Microscopy (SEM)

The surface characterization and microstructure evaluation of GBP was carried out through SEM (JSM-6360LA; JEOL, Tokyo, Japan). Lyophilized GBP was coated with a thin layer of Au and was then evaluated, under vacuum, at an acceleration voltage of 10 kV.

2.3.7. Atomic Force Microscopy (AFM)

GBP was also subjected to atomic force microscopic analysis using a scanning probe microscope (Dimension Icon; Bruker, Germany). GBP dissolved in distilled water at a concentration of 1 µg/mL was sonicated (30 min) and was then pipetted (2–3 µL) onto a mica disc. Afterwards, the disc was dried (120 °C for 30 s) before analysis.

2.3.8. Fourier Transform Infrared Spectroscopy (FT-IR)

After pressing 1 mg of GBP and 100 mg KBr into a pellet, the FT–IR spectrum (MAGNA-IR 750, Thermo Nicolet Co., Waltham, Massachusetts USA) was measured in a fixed frequency range (4000–400 cm−1). The number of scans used was 32, and the spectral resolution was 2 cm−1.

2.4. Antioxidant Potential of GBP

2.4.1. DPPH Radical Scavenging Activity

A previous publication [30], incorporating some modifications, was referred to in order to determine the DPPH radical scavenging potency of GBP. In brief, 0.004% (w/v) DPPH/dehydrated alcohol solution (1 mL) was well mixed with 1 mL GBP (0.25, 0.5, 1, 2 and 4 mg/mL). The reaction mixtures were allowed to react, in the dark, at room temperature for half an hour. Afterwards, the absorbance was measured at 517 nm, while the DPPH radical scavenging effect (%) was derived from a previously reported equation [31].

2.4.2. Hydroxyl Radical (HO) Scavenging Activity

To evaluate the HO scavenging efficacy of GBP, a few amendments were made in a published protocol [32]. In brief, 1 mL each of GBP (0.5, 1, 2, 4 and 8 mg/mL), FeSO4 (9 mmol/L) and ethanol salicylate (9 mmol/L) were mixed to form a 1:1:1 solution. Afterwards, 1 mL of 9 mmol/L H2O2 was introduced preceding incubation (30 min; 37 °C). The absorbance was measured at 510 nm, while the HO scavenging activity (%) was calculated in accordance with a previous report [31].

2.4.3. ABTS Radical Scavenging Activity

GBP was also ascertained for the presence of any ABTS radical scavenging effect according to a published protocol [33], with some alterations. To generate ABTS radicals, 5 mL of 7 mmol/L ABTS was mixed with 88 μL of 149 mmol/L K2S2O8. The resultant reaction mixture was subjected to incubation (dark; 16 h) prior to the addition of this solution (1 mL) to 10 μL of each GBP concentration (0.25, 0.5, 1, 2 and 4 mg/mL). The ABTS radical scavenging activity (%) was determined [34] after measuring the absorbance at 734 nm.

2.5. Statistical Analysis

Each experiment was repeated three times. The values were calculated through Microsoft Excel 2010 and were indicated as the mean ± standard deviation (where relevant).

3. Results and Discussion

3.1. Physical and Chemical Characteristics

The physical and chemical characteristics of GBP are summarized in Table 1. Showing consistency with the results communicated for other species of the genus Gracilaria [19,35], a yield of 24.12% was obtained for GBP. The range of the GBP sulfate content (9.16%) showed a similarity to that reported for G. fisheri [36], G. chouae [19] and G. intermedia [37]. The food, cosmetic and pharmaceutical applications of sulfated polysaccharides extracted from seaweed have been in the limelight during the previous few decades [38]. The total sugar content of GBP (18.84%), however, was quite lower than that reported for G. fisheri (56.33 and 55.63%) [36] and G. chouae (52.63%) [19].
The enormous dissimilarity between the observed setting and melting point for GBP (27.33 °C and 64.33 °C, respectively) corresponds to its good applicability in industrial processes. Being farther apart, such a setting and melting point allow for a high stability amidst increased temperatures during industrial processing [19]. Moreover, a higher melting point also corresponds to a greater utility in hot environments and in baked stuff, which provides more possibilities for GBP when cooking daily diets and in processing and applications within the food industry [39].
Several important indexes for polysaccharide characterization can be obtained from HPSEC-Visc-MALLS-RID analyses. These include Mw and Mn, which correspond to the polymeric chain size and chain length, respectively. The polydispersity index (PDI) is another important parameter that is essentially the ratio of Mw to Mn (Mw/Mn). Yet another important index is represented by the intrinsic viscosity [η], an indication of the solute’s impact on the solution’s viscosity. This index is reportedly related to the polysaccharide’s configuration, its degree of branching and Mw, and the property of the solvent [40]. Similarly, the Mark–Houwink–Sakurada α, Rg and Rh values are significant in revealing vital information about the polysaccharide’s structural conformation. GBP showed an Mw of 6.149 × 105 Da and Mn of 4.169 × 105 Da, indicating that GBP was a polysaccharide of natural origin [41]. A typical symmetric peak showing a slightly wider molecular mass distribution was obtained for GBP (Figure 1), testifying to the degree of dispersion present in it. The GBP was further evident from the observed PDI (1.475). Likewise, an 844.12 mL/g [η] value was evident for GBP. However, low [η] values are generally regarded as highly fermentable [42], but this interpretation is now changing [43]. This evidence has been specifically reported for algal polysaccharides that have a considerably high [η] value [44]. In addition, GBP was found to be a linear polymer exhibiting a random coil conformation, demonstrated by a Mark–Houwink–Sakurada α value of 0.702. This interpretation is based on the accepted values of α for polymers, wherein the α value of 0.5–0.8 represents a malleable random coil conformation, a α value greater than 0.8 denotes semimalleable or extra stretched chains [45], a α value of 0 indicates rigid sphere, one of 2 demonstrates stiff rod, and one of ~0.7 specifies a linear conformation [46]. The linear structure of GBP was also evident from the Rg/Rh value (1.57), where this ratio was ~0.775 for globular polymers, and a higher value demonstrated a correspondingly greater deviation from an orbicular to a more linearly stretched conformation [47].
A substantial AHG content (17.97%) was found in GBP. Numerous biological activities demonstrated by 3,6-anhydrogalactose–galactose (AHG–GAL) oligomers have been primarily linked with AHG content [16]. The AHG–GAL oligomers specifically exhibit immunoregulative, antioxidant, carcinostatic, apoptosis-inductive, antiallergic, hepatoprotective, α-glucosidase-inhibitive and antiinflammation effects [16,48]. Besides, AHG–GAL dimers, neoagarobiose, demonstrate moisturizing and whitening properties [49].
The surface topography of the GBP was illustrated was being rough with a tight structure, but it was not flat. Diverse polymeric chains in a linear conformation having an asymmetrical contour and size were observed (Figure 2A). AFM is an important tool for detecting the morphology of the polysaccharide that the macromolecules originated (Figure 3) [50]. Generally, the size of the polysaccharide molecular chain is about 0.1–1.0 nm [51]. The linearity and random coil conformation of GBP was obvious from the AFM micrograph. A height range of 0.12 to 0.58 nm was noted for GBP particles (average height of 0.30 ± 0.12 nm). Based on the result of the dilute polymer solution theory, the finding that GBP could be evidenced as being a linear polymer from SEM and AFM analysis.
Spectrum analyses from FT–IR established that GBP contained AHG and that it was indeed a sulfated polysaccharide (Figure 4). Alkane C–H stretching was evident at 2940 cm−1, and O–H stretching was observed at 3332 cm−1, while the absorption at 1645 cm−1 corresponded to polymer bound water [52]. Sulfates in GBP were represented by the absorption observed at 1372 cm−1 in the spectrum [53]. The presence of S=O of sulfate esters, on the other hand, was denoted by the absorption at 1249 cm−1 [54]. Similarly, the peaks observed at 1123 cm−1 and 1066 cm−1 could be attributed to the asymmetric stretching of glycosidic bonds [55] and C–O stretching of AHG [54], respectively. The absorption at 930 cm−1, instead, corresponded to the C–O–C stretching of AHG [56]. Moreover, the presence of the C6 group in β-D-galactose was confirmed by the absorption at 890 cm−1 [55]. The absorption at 580 cm−1 likewise represented O=S=O bending [55].

3.2. Antioxidant Studies

Superoxide anion (O2−), hydrogen peroxide (H2O2) and hydroxyl radical (HO) exemplify reactive oxygen species (ROS). These ROS, when accumulated in the body, cause oxidative stress culminating in a number of diseases [57]. Compounds extracted from natural sources, in general, and polysaccharides, in particular, are quite effective in scavenging ROS [58]. A dose-dependent scavenging efficacy was observed for GBP in DPPH, HO and ABTS assays (Figure 5). As the concentration increased from 0.125 to 2.0 mg/mL, the scavenging abilities of GBP increased. A greater scavenging capacity corresponding to 19.80%, 8.80% and 25.42% for DPPH, HO and ABTS radicals, respectively, was observed when GBP was used in the highest tested concentration of 2 mg/mL. Conversely, the lowest tested concentration of GBP (0.125 mg/mL) yielded the least observed DPPH, HO and ABTS scavenging activities (7.71%, 1.75% and 4.46%, respectively). The findings were therefore in good agreement with the electron transfer ability [59] and antioxidant effectivity of polysaccharides [60]. The antioxidant activity of polysaccharides from G. blodgettii might be related to the content of sulfate. Sulfated polysaccharides extracted from other red algae also possessed antioxidant activities. Di found that polysaccharides from Gracilaria rubra with a sulfuric radical of 12.42% presented an excellent antioxidant activity; the scavenging effects of DPPH, ABTS and superoxide anion radical were 30.67%, 55.34% and 72.82%, respectively [61]. The DPPH and hydroxyl radical activities of sulfated polysaccharides from Gracilaria birdiae (a sulfate content of 8.4%) were also exihibited [62].

4. Conclusions

The physical and chemical characterization, and ROS scavenging of GBP were studied in this work. According to the information obtained from the physical and chemical analysis, it was confirmed that GBP was in fact a sulfated polysaccharide occurring in a linear random coil conformation. This study also pointed to the presence of a considerable quantity of AHG in GBP, which is an important bioactive compound for human health. Similarly, the enormous dissimilarity in the setting and melting points observed for GBP echoes its usefulness in relation to functional food industrial processes and an improved shelf-life in hot environments. Furthermore, it is evident that sulfated polysaccharide extracted from G. blodgettii is a promising antioxidant substance in the functional food industry owing to its ROS scavenging efficacy.

Author Contributions

B.M.K. participated in analyses and interpreted the results, along with drafting the manuscript; L.-X.Z. contributed to experimental analyses; Y.L., W.K., and A.A.S. critically revised the final draft; while K.-L.C. conceived and designed the study and approved the final draft for submission. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China, grant number 31901692; the National Natural Science Foundation of Guangdong Province, China, grant number 2018A030310151; and the 2020 Li Ka Shing Foundation Cross-Disciplinary Research Grant, grant number 2020LKSFG02E.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Acknowledgments

The authors acknowledge the financial support in the form of grants from the National Natural Science Foundation of China (31901692), the National Natural Science Foundation of Guangdong Province, China (2018A030310151), and the 2020 Li Ka Shing Foundation Cross-Disciplinary Research Grant (2020LKSFG02E).

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Khan, B.M.; Liu, Y. Marine Mollusks: Food with Benefits. Compr. Rev. Food. Sci. Food Saf. 2019, 18, 548–564. [Google Scholar] [CrossRef] [PubMed]
  2. Wu, S.; Liu, Y.; Jiang, P.; Xu, Y.; Zheng, W.; Song, S.; Ai, C. Effect of sulfate group on sulfated polysaccharides-induced improvement of metabolic syndrome and gut microbiota dysbiosis in high fat diet-fed mice. Int. J. Biol. Macromol. 2020, 164, 2062–2072. [Google Scholar] [CrossRef] [PubMed]
  3. Shi, F.; Tian, X.; McClements, D.J.; Chang, Y.; Shen, J.; Xue, C. Influence of molecular weight of an anionic marine polysaccharide (sulfated fucan) on the stability and digestibility of multilayer emulsions: Establishment of structure-function relationships. Food Hydrocoll. 2020, 113, 106418. [Google Scholar] [CrossRef]
  4. Vanavil, B.; Selvaraj, K.; Aanandhalakshmi, R.; Sri, K.U. Arumugam M.Bioactive and thermostable sulphated polysaccharide from Sargassum swartzii with drug delivery applications. Int. J. Biol. Macromol. 2020, 153, 190–200. [Google Scholar]
  5. Milinovic, J.; Mata, P.; Diniz, M.; Noronha, J.P. Umami taste in edible seaweeds: The current comprehension and perception. Int. J. Gastron. Food Sci. 2021, 23, 100301. [Google Scholar] [CrossRef]
  6. Praveen, M.A.; Parvathy, K.R.K.; Balasubramanian, P.; Jayabalan, R. An overview of extraction and purification techniques of seaweed dietary fibers for immunomodulation on gut microbiota. Trends Food Sci. Technol. 2019, 92, 46–64. [Google Scholar] [CrossRef]
  7. Xu, S.Y.; Huang, X.S.; Cheong, K.-L. Recent Advances in Marine Algae Polysaccharides: Isolation, Structure, and Activities. Mar. Drugs 2017, 15, 388. [Google Scholar] [CrossRef] [Green Version]
  8. Bhadja, P.; Tan, C.Y.; Ouyang, J.M.; Yu, K. Repair Effect of Seaweed Polysaccharides with Different Contents of Sulfate Group and Molecular Weights on Damaged HK-2 Cells. Polymers 2016, 8, 188. [Google Scholar] [CrossRef]
  9. Jayachandran, V.; Sukumaran, A.; Se-Kwon, K.; Min, S.S. Seaweed Polysaccharide-Based Nanoparticles: Preparation and Applications for Drug Delivery. Polymers 2016, 8, 30. [Google Scholar]
  10. Zheng, L.-X.; Chen, X.; Cheong, K.-L. Current trends in marine algae polysaccharides: The digestive tract, microbial catabolism, and prebiotic potential. Int. J. Biol. Macromol. 2020, 151, 344–354. [Google Scholar] [CrossRef]
  11. Zhong, Q.W.; Wei, B.; Wang, S.J.; Ke, S.Z.; Chen, J.W.; Zhang, H.W.; Wang, H. The Antioxidant Activity of Polysaccharides Derived from Marine Organisms: An Overview. Mar. Drugs 2019, 17, 674. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  12. Usov, A. Structural analysis of red seaweed galactans of agar and carrageenan groups. Food Hydrocoll. 1998, 12, 301–308. [Google Scholar] [CrossRef]
  13. McKim, J.M. Food additive carrageenan: Part I: A critical review of carrageenan in vitro studies, potential pitfalls, and implications for human health and safety. Crit. Rev. Toxicol. 2014, 44, 211–243. [Google Scholar] [CrossRef] [PubMed]
  14. Pomin, V.H.J.G.J. Structural and functional insights into sulfated galactans: A systematic review. Glycoconj. J. 2010, 27, 1–12. [Google Scholar] [CrossRef] [PubMed]
  15. Liu, J.; Zhan, X.; Wan, J.; Wang, Y.; Wang, C. Review for carrageenan-based pharmaceutical biomaterials: Favourable physical features versus adverse biological effects. Carbohydr. Polym. 2015, 121, 27–36. [Google Scholar] [CrossRef] [PubMed]
  16. Cheong, K.-L.; Qiu, H.; Du, H.; Liu, Y.; Khan, B.M. Oligosaccharides Derived from Red Seaweed: Production, Properties, and Potential Health and Cosmetic Applications. Molecules 2018, 23, 2451. [Google Scholar] [CrossRef] [Green Version]
  17. Hassan, R.; Othman, M.N.A.; Harith, M.N.; Sah, A.S.R.M. Morphological Diversity of Gracilaria blodgettii Harvey 1853 (Gracilariaceae, Rhodophyta) from Sarawak, Malaysian Borneo. Scientifica 2019, 2019, 3430968. [Google Scholar] [CrossRef] [Green Version]
  18. Yang, M.Y.; Geraldino, P.J.L.; Kim, M.S. DNA barcode assessment of Gracilaria salicornia (Gracilariaceae, Rhodophyta) from Southeast Asia. Bot. Stud. 2013, 54, 27. [Google Scholar] [CrossRef] [Green Version]
  19. Khan, B.M.; Qiu, H.-M.; Wang, X.-F.; Liu, Z.-Y.; Zhang, J.-Y.; Guo, Y.-J.; Chen, W.-Z.; Liu, Y.; Cheong, K.-L. Physicochemical characterization of Gracilaria chouae sulfated polysaccharides and their antioxidant potential. Int. J. Biol. Macromol. 2019, 134, 255–261. [Google Scholar] [CrossRef]
  20. Khan, B.M.; Qiu, H.-M.; Xu, S.-Y.; Liu, Y.; Cheong, K.-L. Physicochemical characterization and antioxidant activity of sulphated polysaccharides derived from Porphyra haitanensis. Int. J. Biol. Macromol. 2020, 145, 1155–1161. [Google Scholar] [CrossRef]
  21. Khan, B.M.; Cheong, K.-L.; Liu, Y. ATPS: “Aqueous two-phase system” as the “answer to protein separation” for protein-processing food industry. Crit. Rev. Food Sci. Nutr. 2019, 59, 3165–3178. [Google Scholar] [CrossRef] [PubMed]
  22. Babbar, N.; Oberoi, H.S.; Uppal, D.S.; Patil, R.T. Total phenolic content and antioxidant capacity of extracts obtained from six important fruit residues. Food Res. Int. 2011, 44, 391–396. [Google Scholar] [CrossRef]
  23. Rodrigo, R.; Miranda, A.; Vergara, L. Modulation of endogenous antioxidant system by wine polyphenols in human disease. Clin. Chim. Acta 2011, 412, 410–424. [Google Scholar] [CrossRef]
  24. Yan, J.-K.; Yu, Y.-B.; Wang, C.; Cai, W.-D.; Wu, L.-X.; Yang, Y.; Zhang, H.-N. Production, physicochemical characteristics, and in vitro biological activities of polysaccharides obtained from fresh bitter gourd (Momordica charantia L.) via room temperature extraction techniques. Food Chem. 2021, 337, 127798. [Google Scholar] [CrossRef] [PubMed]
  25. Patel, S. Therapeutic importance of sulfated polysaccharides from seaweeds: Updating the recent findings. 3 Biotech 2012, 2, 171–185. [Google Scholar] [CrossRef] [Green Version]
  26. Torres, P.; Santos, J.P.; Chow, F.; Santos, D.Y.A.C.d.S. A comprehensive review of traditional uses, bioactivity potential, and chemical diversity of the genus Gracilaria (Gracilariales, Rhodophyta). Algal Res. 2019, 37, 288–306. [Google Scholar] [CrossRef]
  27. Zhang, Z.; Zhang, Q.; Wang, J.; Song, H.; Zhang, H.; Niu, X. Chemical modification and influence of function groups on the in vitro-antioxidant activities of porphyran from Porphyra haitanensis. Carbohydr. Polym. 2010, 79, 290–295. [Google Scholar] [CrossRef]
  28. Peasura, N.; Laohakunjit, N.; Kerdchoechuen, O.; Wanlapa, S. Characteristics and antioxidant of Ulva intestinalis sulphated polysaccharides extracted with different solvents. Int. J. Biol. Macromol. 2015, 81, 912–919. [Google Scholar] [CrossRef]
  29. Jol, C.N.; Neiss, T.G.; Penninkhof, B.; Rudolph, B.; De Ruiter, G.A. A novel high-performance anion-exchange chromatographic method for the analysis of carrageenans and agars containing 3, 6-anhydrogalactose. Anal. Biochem. 1999, 268, 213–222. [Google Scholar] [CrossRef]
  30. Sun, H.-H.; Mao, W.-J.; Chen, Y.; Guo, S.-D.; Li, H.-Y.; Qi, X.-H.; Chen, Y.-L.; Xu, J. Isolation, chemical characteristics and antioxidant properties of the polysaccharides from marine fungus Penicillium sp. F23-2. Carbohydr. Polym. 2009, 78, 117–124. [Google Scholar] [CrossRef]
  31. Song, H.; He, M.; Gu, C.; Wei, D.; Liang, Y.; Yan, J.; Wang, C. Extraction Optimization, Purification, Antioxidant Activity, and Preliminary Structural Characterization of Crude Polysaccharide from an Arctic Chlorella sp. Polymers 2018, 10, 292. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  32. Chen, Y.-X.; Liu, X.-Y.; Xiao, Z.; Huang, Y.-F.; Liu, B. Antioxidant activities of polysaccharides obtained from Chlorella pyrenoidosa via different ethanol concentrations. Int. J. Biol. Macromol. 2016, 91, 505–509. [Google Scholar] [CrossRef] [PubMed]
  33. Re, R.; Pellegrini, N.; Proteggente, A.; Pannala, A.; Yang, M.; Rice-Evans, C. Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radic. Biol. Med. 1999, 26, 1231–1237. [Google Scholar] [CrossRef]
  34. Falkeborg, M.; Cheong, L.-Z.; Gianfico, C.; Sztukiel, K.M.; Kristensen, K.; Glasius, M.; Xu, X.; Guo, Z. Alginate oligosaccharides: Enzymatic preparation and antioxidant property evaluation. Food Chem. 2014, 164, 185–194. [Google Scholar] [CrossRef] [PubMed]
  35. Marinho-Soriano, E. Agar polysaccharides from Gracilaria species (Rhodophyta, Gracilariaceae). J. Biotechnol. 2001, 89, 81–84. [Google Scholar] [CrossRef]
  36. Imjongjairak, S.; Ratanakhanokchai, K.; Laohakunjit, N.; Tachaapaikoon, C.; Pason, P.; Waeonukul, R. Biochemical characteristics and antioxidant activity of crude and purified sulfated polysaccharides from Gracilaria fisheri. J. Biotechnol. 2016, 80, 524–532. [Google Scholar]
  37. Castro, J.P.L.d.; Costa, L.E.C.; Pinheiro, M.P.; Francisco, T.; Vasconcelos, P.H.M.; Funari, L.M.; Daudt, R.M.; Santos, G.R.C.; Cardozo, N.S.M.; Freitas, A.L.P. Polysaccharides of red alga Gracilaria intermedia: Structure, antioxidant activity and rheological behavior. Polímeros 2018, 28, 178–186. [Google Scholar] [CrossRef]
  38. Cunha, L.; Grenha, A. Sulfated seaweed polysaccharides as multifunctional materials in drug delivery applications. Mar. Drugs 2016, 14, 42. [Google Scholar] [CrossRef]
  39. Pegg, A.M. The application of natural hydrocolloids to foods and beverages. In Natural Food Additives, Ingredients and Flavourings; Baines, D., Seal, R., Eds.; Woodhead Publishing Limited: Cambridge, UK, 2012; pp. 175–196. [Google Scholar]
  40. Hui, Z.; Nie, S.; Guo, Q.; Wang, Q.; Cui, S.W.; Xie, M. Conformational properties of a bioactive polysaccharide from Ganoderma atrum by light scattering and molecular modeling. Food Hydrocoll. 2018, 84, 16–25. [Google Scholar]
  41. Carraher, C.E. Seymour/Carraher’s Polymer Chemistry, 6th ed.; Marcel Dekker Inc.: New York, NY, USA, 2003. [Google Scholar]
  42. Molin, U.; Daniel, G. Effects of refining on the fibre structure of kraft pulps as revealed by FE-SEM and TEM: Influence of alkaline degradation. Holzforschung 2004, 58, 226–232. [Google Scholar] [CrossRef]
  43. Phillips, G.O. Dietary fibre: A chemical category or a health ingredient? Bioact. Carbohydr. Diet. Fibre 2013, 1, 3–9. [Google Scholar] [CrossRef]
  44. Xu, S.-Y.; Aweya, J.J.; Li, N.; Deng, R.-Y.; Chen, W.-Y.; Tang, J.; Cheong, K.-L. Microbial catabolism of Porphyra haitanensis polysaccharides by human gut microbiota. Food Chem. 2019, 289, 177–186. [Google Scholar] [CrossRef] [PubMed]
  45. Harding, S.E.; Abdelhameed, A.S.; Morris, G.A. On the hydrodynamic analysis of conformation in mixed biopolymer systems. Polym. Int. 2011, 60, 2–8. [Google Scholar] [CrossRef] [Green Version]
  46. Hiemenz, P.C.; Lodge, T.P. Polymer Chemistry, 2nd ed.; CRC Press: Boca Raton, FL, USA, 2007. [Google Scholar]
  47. Tande, B.; Wagner, N.J.; Mackay, M.E.; Hawker, C.J.; Jeong, M. Viscosimetric, hydrodynamic, and conformational properties of dendrimers and dendrons. Macromolecules 2001, 34, 8580–8585. [Google Scholar] [CrossRef]
  48. Chen, H.; Yan, X.; Zhu, P.; Lin, J. Antioxidant activity and hepatoprotective potential of agaro-oligosaccharides in vitro and in vivo. Nutr. J. 2006, 5, 31. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  49. Kobayashi, R.; Takisada, M.; Suzuki, T.; Kirimura, K.; Usami, S. Neoagarobiose as a novel moisturizer with whitening effect. Biosci. Biotechnol. Biochem. 1997, 61, 162–163. [Google Scholar] [CrossRef] [Green Version]
  50. Wang, K.-p.; Wang, J.; Li, Q.; Zhang, Q.; You, R.; Cheng, Y.; Luo, L.; Zhang, Y. Structural differences and conformational characterization of five bioactive polysaccharides from Lentinus edodes. Food Res. Int. 2014, 62, 223–232. [Google Scholar] [CrossRef]
  51. Wang, Y.; Peng, Y.; Wei, X.; Yang, Z.; Xiao, J.; Jin, Z. Sulfation of tea polysaccharides: Synthesis, characterization and hypoglycemic activity. Int. J. Biol. Macromol. 2010, 46, 270–274. [Google Scholar] [CrossRef]
  52. Şen, M.; Erboz, E.N. Determination of critical gelation conditions of κ-carrageenan by viscosimetric and FT-IR analyses. Food Res. Int. 2010, 43, 1361–1364. [Google Scholar] [CrossRef]
  53. Rochas, C.; Lahaye, M.; Yaphe, W. Sulfate content of carrageenan and agar determined by infrared spectroscopy. Bot. Mar. 1986, 29, 335–340. [Google Scholar] [CrossRef]
  54. Pereira, L.; Amado, A.M.; Critchley, A.T.; van de Velde, F.; Ribeiro-Claro, P.J. Identification of selected seaweed polysaccharides (phycocolloids) by vibrational spectroscopy (FTIR-ATR and FT-Raman). Food Hydrocoll. 2009, 23, 1903–1909. [Google Scholar] [CrossRef] [Green Version]
  55. Sekkal, M.; Legrand, P. A spectroscopic investigation of the carrageenans and agar in the 1500-100 cm− 1 spectral range. Spectrochim. Acta Part A Mol. Spectrosc. 1993, 49, 209–221. [Google Scholar] [CrossRef]
  56. Prado-Fernández, J.; Rodrıguez-Vázquez, J.; Tojo, E.; Andrade, J. Quantitation of κ-, ι-and λ-carrageenans by mid-infrared spectroscopy and PLS regression. Anal. Chim. Acta 2003, 480, 23–37. [Google Scholar] [CrossRef]
  57. Grice, H.C. Safety evaluation of butylated hydroxytoluene (BHT) in the liver, lung and gastrointestinal tract. Food Chem. Toxicol. 1986, 24, 1127–1130. [Google Scholar]
  58. Wu, X.; Li, R.; Zhao, Y.; Liu, Y. Separation of polysaccharides from Spirulina platensis by HSCCC with ethanol-ammonium sulfate ATPS and their antioxidant activities. Carbohydr. Polym. 2017, 173, 465–472. [Google Scholar] [CrossRef]
  59. Khaskheli, S.G.; Zheng, W.; Sheikh, S.A.; Khaskheli, A.A.; Liu, Y.; Soomro, A.H.; Feng, X.; Sauer, M.B.; Wang, Y.F.; Huang, W. Characterization of Auricularia auricula polysaccharides and its antioxidant properties in fresh and pickled product. Int. J. Biol. Macromol. 2015, 81, 387–395. [Google Scholar] [CrossRef]
  60. Cai, C.; Yang, Y.; Zhao, M.; Jia, R.; Jiao, B.; He, P. Extraction and antioxidation of polysaccharide from Porphyra haitanensis using response surface method. Pak. J. Bot. 2017, 49, 1137–1141. [Google Scholar]
  61. Di, T.; Chen, G.; Sun, Y.; Ou, S.; Zeng, X.; Ye, H. Antioxidant and immunostimulating activities in vitro of sulfated polysaccharides isolated from Gracilaria rubra. J. Funct. Food. 2017, 28, 64–75. [Google Scholar] [CrossRef]
  62. Souza, B.W.S.; Cerqueira, M.A.; Bourbon, A.I.; Pinheiro, A.C.; Martins, J.T.; Teixeira, J.A.; Coimbra, M.A.; Vicente, A.A. Chemical characterization and antioxidant activity of sulfated polysaccharide from the red seaweed Gracilaria birdiae. Food Hydrocoll. 2012, 27, 287–292. [Google Scholar] [CrossRef] [Green Version]
Polymers 13 00442 g001 550
Figure 1. Molecular weight distribution depicted by HPSEC-Visc-MALLS-RID of G. blodgettii polysaccharide.
Figure 1. Molecular weight distribution depicted by HPSEC-Visc-MALLS-RID of G. blodgettii polysaccharide.
Polymers 13 00442 g001
Polymers 13 00442 g002 550
Figure 2. Scanning electron micrograph of G. blodgettii polysaccharide: magnification (A) 200×; (B) magnification 2000×.
Figure 2. Scanning electron micrograph of G. blodgettii polysaccharide: magnification (A) 200×; (B) magnification 2000×.
Polymers 13 00442 g002
Polymers 13 00442 g003 550
Figure 3. Atomic force micrograph of G. blodgettii polysaccharide: (A) 2D; (B) 3D; (C) height distribution graph.
Figure 3. Atomic force micrograph of G. blodgettii polysaccharide: (A) 2D; (B) 3D; (C) height distribution graph.
Polymers 13 00442 g003
Polymers 13 00442 g004 550
Figure 4. Fourier transform infrared spectra of G. blodgettii polysaccharide.
Figure 4. Fourier transform infrared spectra of G. blodgettii polysaccharide.
Polymers 13 00442 g004
Polymers 13 00442 g005 550
Figure 5. (A) DPPH scavenging effect, (B) HO scavenging effect and (C) ABTS scavenging effect of G. blodgettii polysaccharide (mean ± standard deviation, n = 3).
Figure 5. (A) DPPH scavenging effect, (B) HO scavenging effect and (C) ABTS scavenging effect of G. blodgettii polysaccharide (mean ± standard deviation, n = 3).
Polymers 13 00442 g005
Table
Table 1. Physical and chemical characteristics of G. blodgettii polysaccharides.
Table 1. Physical and chemical characteristics of G. blodgettii polysaccharides.
IndexValuesIndexValues
Yield (%)24.12 ± 0.59 *Molecular weight, Mn (Da)4.169 × 105
Sulfate content (%)9.16 ± 0.59 *Polydispersity (Mw/Mn)1.475
Total sugar (%)18.84 ± 0.83 *Intrinsic viscosity (mL/g)844.12
Setting point (°C)27.33 ± 0.65 *Mark–Houwink–Sakurada α0.702
Melting point (°C)64.33 ± 6.51 *Hydrodynamic radius (nm)41.763
3,6-anhydro-galactose (%)17.97 ± 0.46 *Radius of gyration (nm)65.6
Molecular weight, Mw (Da)6.149 × 105
* mean ± standard deviation, n = 3.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Khan, B.M.; Zheng, L.-X.; Khan, W.; Shah, A.A.; Liu, Y.; Cheong, K.-L. Antioxidant Potential of Physicochemically Characterized Gracilaria blodgettii Sulfated Polysaccharides. Polymers 2021, 13, 442. https://doi.org/10.3390/polym13030442

AMA Style

Khan BM, Zheng L-X, Khan W, Shah AA, Liu Y, Cheong K-L. Antioxidant Potential of Physicochemically Characterized Gracilaria blodgettii Sulfated Polysaccharides. Polymers. 2021; 13(3):442. https://doi.org/10.3390/polym13030442

Chicago/Turabian Style

Khan, Bilal Muhammad, Li-Xin Zheng, Wajid Khan, Aftab Ali Shah, Yang Liu, and Kit-Leong Cheong. 2021. "Antioxidant Potential of Physicochemically Characterized Gracilaria blodgettii Sulfated Polysaccharides" Polymers 13, no. 3: 442. https://doi.org/10.3390/polym13030442

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop