The aim of this study was to study the conformational changing when sulfated groups were introduced to the molecular chain of native tamarind seed polysaccharide (TSP). Light Scattering (LS) method was used to determine conformation of TSP and its sulfated derivative TSPS. The results indicated that both TSP and TSPS have a highly branched and more sphere-like molecule; however, after sulfation, the TSPS became more branched structure than native polysaccharide. Keywords. Tamarind seed polysaccharide, conformation, light scattering

Minh Thu, Quach Thi

Tan, Bui Ngo

Thu Thuy, Thanh Thi

Vietnam Academy of Science and Technology: Journals Online

 Vietnam Journal of Chemistry, International Edition, 55(2): 236-239, 2017 
DOI: 10.15625/2525-2321.2017-00451 
236 
 
 
 
Study on conformational structure of tamarind seed polysaccharide  
and its sulfated derivative by light scattering method  
Bui Ngoc Tan
1,2
, Quach Thi Minh Thu
2
, Thanh Thi Thu Thuy
2*
 
1Hai Phong University of Medicine and Pharmacy 
2Institute of Chemistry Vietnam Academy of Science and Technology 
Received 15 July 2016; Accepted for publication 11 April 2017 
 
Abstract 
The aim of this study was to study the conformational changing when sulfated groups were introduced to the 
molecular chain of native tamarind seed polysaccharide (TSP). Light Scattering (LS) method was used to determine 
conformation of TSP and its sulfated derivative TSPS. The results indicated that both TSP and TSPS have a highly 
branched and more sphere-like molecule; however, after sulfation, the TSPS became more branched structure than 
native polysaccharide. 
Keywords. Tamarind seed polysaccharide, conformation, light scattering. 
 
1. INTRODUCTION 
 
Tamarind seed polysaccharide (TSP) belongs to 
xyloglucan family obtained from the seed of 
tamarind tree Tamarindus indica. TSP possesses 
properties like high viscosity, broad pH tolerance, 
noncarcinogenicity, mucoadhesive nature, and 
biocompatibility; therefore, it is used as stabilizer, 
suspending agent, thickener, gelling agent, and 
binder in food and pharmaceutical industries [1, 2]. 
Polysaccharides are known to reveal the 
biological functions by forming a specific 
conformation. For example, branched poly- (1 3)-
D-Glucan has a strong anti-tumor activity, which 
may be associated with its specific chain 
conformation, while curdlan, a linear poly- (1 3)-
D-Glucan, has no anti-tumor activity although it 
assumes a triple-stranded helical conformation, but 
by sulfation, curdlan sulfate has anti-HIV activity 
[3]. Therefore, the elucidations of the molecular 
structure for both chemical structure and 
conformation can expand the application of a 
particular polysaccharide. 
With the development of high-resolution 
instrumental processes, such as scattering techniques 
(i.e. light scattering, x-ray and neutron scattering), it 
is possible to study the conformation of a 
polysaccharide at the molecular level. Light 
scattering (LS) is a powerful technique that can 
provide structural information of high-resolution 
structures, and determine the conformation of 
molecule in solution [4]. 
In our previous paper [5, 6], the chemical 
structure of TSP was determined and a sulfated 
derivative of TSP was produce, the result showed 
that the sulfation of TSP enhances the antitumor 
activity of the polysaccharide. In this work, we aim 
to know the conformational changing when sulfate 
groups were introduced to the molecular chain of 
native TSP, here, Light Scattering (LS) method 
including both static and dynamic techniques was 
used to determine conformation of TSP and TSPS. 
 
2. MATERIALS AND METHODS 
 
2.1. Materials  
 
Tamarind seed polysaccharide TSP: Tamarind 
seed was collected at Thuy-nguyen (Hai-phong) in 
May, 2013. The extraction of TSP from tamarind 
seed kernel followed the method of R. Deveswaran 
et al. [7] and has been reported in our previous paper 
[5]. The yield of extraction was 38.7 % calculated 
based on dried tamarind seed kernel weight.   
Sulfated derivative TSPS: The sulfation was 
following the method of Lihong Fan et al. [8]. 
Determination of sulfate content was followed the 
gravimetric method [9]. The structure of sulfated 
derivative (TSPS) was confirmed by IR and NMR 
spectra. The results showed that TSP was sulfated to 
give a sulfate polysaccharide TSPS with a sulfate 
content of 26.2 %. The details of this study can be 
found in our previous work [6] 
 VJC, 55(2), 2017  Thanh Thi Thu Thuy et al. 
237 
2.1. Gel Permeation Chromatography (GPC) 
measurement 
 
GPC measurements were performed on an HPLC 
Agilent 1100 with a refractive index detector RID at 
30 oC. The eluent was 0.1 N NaNO3 with flow rate of 
1.0 mL/min. The sample concentration was 1 mg/ml. 
Pullulan was used as a standard sample. 
 
2.2. Light Scattering (LS) measurement 
 
The LS measurements were performed at every 
5° in the range 30 -150  on an SLS-6500 & EDLS-
9000 spectrometer installed at the Osaka Electro-
Communication, Japan. The light source is a He-Ne 
laser ( o= 632.8 nm), and the spectrometer was 
calibrated using toluene as a primary standard. 
Cylindrical cells immersed in toluene at 25.0 0.2 ºC 
were used for all the measurements. The alignment 
of the instrument was performed regularly by 
measuring of the light scattering of toluene in the 
range of angles described above. These solutions 
were filtered several times through 0.45 µm MF 
filters (Millipore) to remove dust from the solutions. 
The refractive index increments (dn/dc) of the 
solutions were measured at  = 632.8 nm using a 
Brice-Phoenix differential refractometer.  The data 
were analyzed by the conventional Zimm’s method 
[8], which is a general procedure for the 
determination of the radius of gyration, Rg, the 
average molecular weight, Mw, and the 
hydrodynamic radius, Rh.  The  value, defined as a 
ratio of Rg to Rh (  = Rg/Rh), was also determined in 
order to establish the shape of a solute molecule [4]. 
 
3. RESULTS AND DISCUSSION 
 
Chemical structure of TSP was determined [5], 
TSP is a galactoxyloglucan composed of (1 4)- -
Glucan backbone substituted with side chains of -
Xylopyranose and -Galactopyranosyl (1 2)- -
Xylopyranose linked (1 6) to glucose residues 
(figure 1).  
The structure of native TSP and its sulfated 
derivative was confirmed by IR and NMR spectra 
and the results indicated that some hydroxyl groups 
of glucose, xylose and galactose of TSP were 
sulfated and sulfation enhances the antitumor 
activity of TSP [6]. 
 
Xyl
Glc Glc Glc
Gal Xyl  
Figure 1: Chemical structure of TSP  
 
Molecular weight Mw and molecular weight 
distribution Mw/Mn were determined by GPC. Like 
other native sulfate polysaccharides, the molecular 
weight distribution of the TSP is highly polydisperse 
with Mw/Mn = 4.36 and Mw = 1.155×10
6. The 
literature reports a very wide range of molecular 
weights of TSP samples from 1.15×105 to 2.5×106, 
mostly explainable as differences in the extraction 
processes, polydispersity of the samples [10]. The 
weight average molecular weight Mw of TSPS is 
2.96×105, the result indicated that under sulfation 
process, the native polysaccharide was hydrolyzed. 
The chromatograms of GPC measurements for TSP 
and TSPS are shown in figure 2a and b, respectively. 
Conformational characteristic of TSP and TSPS 
are determined by SLS and DLD. The Zimm plots 
from light scattering measurement of TSP for static 
and dynamic light scattering measurements (SLS 
and DLS) are shown in figures 3a and 3b, 
respectively. The structural parameters estimated 
from GPC and LS measurement were summarized in 
table 1. The relationship between ρ value estimated 
from LS measurement and molecular architecture 
has been extensively summarized by Burchard [4]. 
Generally, Rh increases with branching due to a 
higher segment density, and thus branched chain 
will have a smaller ρ value than a linear chain. The  
value of TSP and TSPS are 0.92 and 1.16, 
respectively, indicated that both TSP and TSPS have 
a highly branched and more sphere-like molecule, 
similar conformational characteristics with other 
plant polysaccharides from soybean [11] and 
flaxseed [12]. After sulfation, TSPS has a large  
value indicating that TSPS have a more branched 
structure than that of TSP. The schematic 
conformation of TSP and TSPS are simulated in 
figures 4a and 4b, respectively. 
Table 1: Results estimated from GPC and LS measurement 
Sample dn/dc (ml/g) Mw x 10
-5 Mw/Mn Rg (nm) Rh (nm)  (=Rg/Rh) 
TSP 0.137 11.55 4.36 211.7 229.4 0.92 
TSPS 0.161 2.69 1.52 216.6 186.4 1.16 
 VJC, 55(2), 2017  Study on conformational structure of… 
238 
 
Figure 2: GPC chromatogram of TSP (a) and TSPS (b)  
 
 
Figure 3: Zim plots for SLS (a) and DLS (b) of TSP 
 
 
Figure 4: Schematic conformation of TSP (a)  
and TSPS (b) 
 
4. CONCLUSION 
 
Conformational structure of TSP and its sulfated 
derivative TSPS was determined by LS method. The 
results indicated that both TSP and TSPS have a 
highly branched and more sphere-like molecule, 
however, after sulfation, the TSPS became more 
branched structure than native one. Our results 
contributed to confirm that chemical modification 
affected not only biological activity, but also 
conformation of native polysaccharides. 
 
Acknowledgment. We thank Dr. Yoshiaki Yuguchi 
of Osaka Electro-Communication University, Japan 
for LS measurements. 
 
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Corresponding author: Thanh Thi Thu Thuy 
Institute of Chemistry 
Vietnam Academy of Science and Technology 
No. 18, Hoang Quoc Viet, Cau Giay District, Hanoi 
E-mail: thuyttt@ich.vast.vn; Telephone number: 0982262005 / 04-37563788. 
  


Study on conformational structure of tamarind seed polysaccharide and its sulfated derivative by light scattering method

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Study on conformational structure of tamarind seed polysaccharide and its sulfated derivative by light scattering method

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