Corresponding author: Ellya Sinurat ( ellya_sinurat@yahoo.com ) Academic editor: Plamen Peikov
© 2021 Sofa Fajriah, Ilmi Fadhilah Rizki, Ellya Sinurat.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Fajriah S, Rizki IF, Sinurat E (2021) Characterization and analysis of the antidiabetic activities of sulphated polysaccharide extract from Caulerpa lentillifera. Pharmacia 68(4): 869-875. https://doi.org/10.3897/pharmacia.68.e73158
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Caulerpa lentillifera is a type of green seaweed that is cultivated in tropical and subtropical areas. The objectives of this study were to determine the characteristics of the sulfated polysaccharides from C. lentillifera and evaluate its antidiabetic activity. In the initial process of this study, samples were macerated with ethanol (1:10). Then, the maceration residue was extracted with an accumulator at 75 °C for three hours. The crude extract yield was 4.16% based on weight seaweed. Ion chromatography purification with DEAE-Sepharose resin provided a yield of 14.8% of crude extract. The monomer analysis of C. lentillifera from the crude extract and purified extract revealed that galactose monomers were dominant and glucose was a minor component. The total carbohydrate and sulfate contents of purified C. lentillifera were higher than those of crude C. lentillifera. Bioactivity tests revealed that purified polysaccharides had higher antidiabetic activity against α-glucosidase enzyme than crude ones with IC50 values of 134.81± 2.0 µg/mL. Purified sulfated polysaccharides of C. lentillifera could potentially be used as an antidiabetic medication.
antidiabetic bioactivity, Caulerpa lentillifera, sulfated polysaccharide, alpha-glucosidase
Chronic hyperglycemia due to diabetes mellitus can lead to defects in insulin levels (
The human digestion process occurs in the small intestine under the mediation of α-amylase and α-glucosidase. Carbohydrate hydrolysis causes a sudden increase in postprandial blood concentration. Maltose and isomaltose are produced by the action of α-amylase and are then hydrolyzed by α-glucosidase, a membrane-generated enzyme in the small intestinal epithelium. The enzyme α-glucosidase is a catalyst in the digestion of carbohydrates in the final stages. Therefore, inhibiting α-glucosidase can inhibit the hydrolysis of carbohydrates from suppressing postprandial hyperglycemia (
C. lentillifera was obtained from Takalar, South of Sulawesi, Indonesia. This plant was determined at Research Center for Oceanography LIPI with voucher specimen RL-01. Seaweed was dried in a vacuum oven after rinsing thoroughly, dried, and then ground. The ground powder was passed through a 60 mesh. The powder in the container was not allowed to contact air (Jime et al. 2001;
The extraction process began with the maceration of seaweed powder (100 g) in ethanol at a ratio of 1:10 for 24 h. Then, the maceration mixture was filtered by using a 250-nylon mesh. Next, the solid residue was extracted using water solvent at 70–80 °C with stirring for three h. The solution was filtered, mixed with ethanol at a ratio of 2:1, and then allowed to settle. The mixture was centrifuged at 8000 xg and 4 °C for 20 min. The formed solid particles were dried in a dryer oven at 60 °C and designated as the extract of C. lentillifera, as shown in Fig.
One gram of polysaccharide extract was dissolved in 50 mL and then heated at 80 °C. Sulfated polysaccharides were extracted through ion chromatography by using DEAE-Sepharose 6B-Cl resin in a 2.5 cm-column in diameter and 40 cm in length and eluted with a gradient of NaCl solution from 0.5 M to 2.5 M. The eluent was collected in 10 mL vials; each eluent concentration is obtained five vials and divided into fractions based on absorbance following the modified method of (
The functional groups of crude extract and purified C. lentillifera were identified with infrared spectroscopic analysis using a Perkin Elmer Spectrum One FTIR Spectrometer. FTIR spectra were recorded over the range of 450–4000 cm−1 at room temperature.
The monomer analysis of crude and purified extracts was performed by dissolving 10 mg of samples in 1.5 M TFA at a ratio of 1:1. The mixture was heated at the temperature of 121 °C for 120 min using a heater. The mixture was neutralized with 10% NaOH and then centrifuged at 8000 xg for 20 min. The pH of the mixture was adjusted with 10% NaOH, and solids were precipitated by centrifugation for 20 min at 4 °C. Monomers in the supernatant were characterized using a Prominence-20 HPLC instrument (Shimadzu Protruding-20) with an Agilent Hi-Plex H column; diameter 7.8 mm; length 300 mm; temperature column at 65-85 °C. The samples solution for hydrolysis treatment was spiked with monosaccharide standards (galactose, rhamnose, xylose, glucose, and mannose) at varying concentrations (100-1000 ppm). About 20 µL of each sample was injected into the column with a 0.6 mL/min flow rate for 20 minutes using 0.005 M H2SO4 as eluent. The Refractive Index Detector (RID-10A) Merck Shimadzu was maintained at 55°C. D-Glucose ≥ 95.5%, D-xylose ≥ 99%, D-mannose ≥ 99%, D-galactose ≥ 99%, and D-fructose ≥ 99% with concentrations of 100–1000 ppm used as standard monomers. All standards monosaccharides purchased from Sigma-Aldrich (St. Louis, MO, USA) distributor in Jakarta. The method of analysis monomer was modified from a previous report (
1H- NMR spectra of crude and purified sulfated polysaccharides were recorded with JEOL ECZR500 operating at 500 MHz using D2O as a solvent using deuterated solvent (δH 4.60) peak of D2O as the reference standard. The experimental properties of this analysis were relaxation delay at 5s, total scan number 24, and temperature at 70°C.
In the presence of enzymes
α-glucosidase inhibitory activity was evaluated according to the previously reported method (
In the absence of enzymes
The procedure used for the blank treatment of quercetin and sample solutions was the same as that used for the treatment with the addition of enzymes, except that enzymes were not added. Instead, 250 µL of dimethyl sulfoxide was added to the samples to compensate for the lost volume. The samples were measured with a UV–Vis spectrophotometer at a wavelength of 400 nm.
α-glucosidase inhibitory activity was calculated as percent inhibition with the following formula (
Note: Absorbance control = absorbance value in the control solution; Absorbance samples = absorbance value in the samples solution.
The polysaccharide extraction yield reached 4.16%. The dried deposits from each fraction had weights of 16.5 mg (FP1), 72.7 mg (FP2), and 18.8 mg (FP3). The results for the fractionation of the purified carbohydrate by using ion resin chromatography are presented in Figure
The spectra of polysaccharides from C. lentillifera are presented in Figure
The glycosidic bond in C1–O–C4 was found between 1200 and 900 cm−1 (
The total polysaccharide purification and polysaccharide extraction rate are shown in Figure
Total carbohydrates in crude were 35.63 ±1.28% and purified 40.51 ±1.23% of C. lentillifera.
The high total carbohydrate content resulted in high load density due to sulfate bonds. The number of sulfate groups bound to the branch chain of polysaccharides was the key to high bioactivity (
Galactose monomers dominated the monomer composition of crude and purified sulfated polysaccharides. The data in Table 1 showed that galactose had a retention time of 9.575 min; compared to the standard galactose, the same retention time of 9,575 minutes and an area of 3.13%. Then glucose had a retention time of 8.988 min compared to glucose standard, the same retention time of 8.988 min, and an area of 1.88%.
Composition of monomer constituents of a crude sulfated polysaccharide extract from C. lentillifera.
No | Name | Retention time | Area | % Area | Height | Int Type | Peak Type |
1 | Unknown | 6.829 | 1939764 | 94.99 | 89817 | bV | Unknown |
2 | Glucose | 8.988 | 38304 | 1.88 | 2855 | VV | Found |
3 | Galactose | 9.579 | 64004 | 3.13 | 4366 | VB | Found |
The standard galactose curve equation showed that the crude and purified polysaccharide samples had galactose contents of 598.99 ±6.4 ppm and 886.63 ±8.5 ppm, respectively. The chromatograms showed that the crude polysaccharides contained glucose monomers at a concentration of 380.31 ±4.2 ppm. By contrast, glucose was present at trace amounts of 0.33% in the purified sulfated polysaccharides. This amount was so small that it was considered non-existent. Research has shown that sugar components in sulfated polysaccharides play a role in bioactivity.
Composition of monomer constituents of purified sulfated polysaccharides of C. lentillifera.
No | Name | Retention time | Area | % Area | Height | Int Type | Peak Type |
1 | 6.831 | 1913942 | 94.92 | 89190 | bV | Unknown | |
2 | 8.767 | 6713 | 0.33 | 447 | VV | Unknown | |
3 | Galactose | 9.577 | 95705 | 4.75 | 6460 | VB | Found |
Another study reported that the constituent monomers of C. lentillifera from the South China Sea consisted of xylose, galactose, glucose and glucuronic acid (
1H-NMR spectroscopy was performed for the structural analysis of mono-, oligo- or polysaccharides (Figure
1H-NMR was also used to identify sugars and specific sugars (
This test aimed to determine the inhibitory effect of sulfated polysaccharides on the enzyme α-glucosidase. The test results were interpreted as IC50 values, which indicated the dose of the sulfated polysaccharide needed to inhibit 50% of enzyme activity. The antidiabetic activity was analyzed by using the principle of the inhibition of the enzyme α-glucosidase. Then, the percentage of inhibition was determined by using a UV–Vis spectrophotometer at a wavelength of 400 nm. The percent inhibition by purified extracts increased relative to that by crude extracts as the concentrations of the extracts were varied from 200, 100, and 50 to 25 µg/mL. In the antidiabetic activity test, the percent inhibition was calculated by obtaining the difference between the absorbance of the control and the sample, then divided by the absorbance of the sample and multiplied by 100%. The percent inhibition results shown in Figure
The data obtained showed that the purified extracts had higher percent inhibition than the crude extracts from C. lentillifera (Figure
The α-glucosidase enzyme had amino acid residues that were predicted to be its active sites. These amino acids were glycine, methionine, aspartic acid, isoleucine, asparagine, tryptophan, lysine, serine, phenylalanine, leucine, arginine, alanine, proline, glutamine, histidine, valine, and glutamic acid. A compound targets the active site of α-glucosidase for inhibition. Quercetin, which is used as a standard in α-glucosidase enzyme inhibition testing with IC50 value 2.07± 0.0 µg/mL, is one of the flavonoid compounds that can inhibit the α-glucosidase enzyme in vitro (
Sulfated polysaccharide extracts from C. lentillifera presented various characteristics and peaks at wave numbers that indicated the presence of sulfate ester groups. The monomer that constituted the sulfated polysaccharides of C. lentillifera included galactose, which was included in the composition of D-galactose-6-sulfate. The in vitro α-glucosidase enzyme inhibition test showed that the purified sulfated polysaccharide had higher activity than the crude sulfated polysaccharide.
We wish to thank to Research Center for Chemistry, National Agency and Research Innovation (BRIN) for providing a financial support through National Priority of Traditional Medicine at Engineering Science Deputy (26/A/DT/2021).