2012_Designed optimization of a single-step extraction of fucose-containing sulfated polysaccharides from Sargassum sp

Designed optimization of a single-step extraction
of fucose-containing sulfated polysaccharides
from Sargassum sp.
Marcel Tutor Ale & Jørn Dalgaard Mikkelsen &
Anne S. Meyer
Received: 20 March 2011 /Revised and accepted: 18 May 2011
# Springer Science+Business Media B.V. 2011
Abstract Fucose-containing sulfated polysaccharides can
be extracted from the brown seaweed, Sargassum sp. It has
been reported that fucose-rich sulfated polysaccharides
from brown seaweeds exert different beneficial biological
activities including anti-inflammatory, anticoagulant, and
anti-viral effects. Classical extraction of fucose-containing
sulfated polysaccharides from brown seaweed species typi-
cally involves extended, multiple-step, hot acid, or CaCl2
treatments, each step lasting several hours. In this work, we
systematically examined the influence of acid concentration
(HCl), time, and temperature on the yield of fucose-
containing sulfated polysaccharides (FCSPs) in statistically
designed two-step and single-step multifactorial extraction
experiments. All extraction factors had significant effects on
the fucose-containing sulfated polysaccharides yield, with
the temperature and time exerting positive effects, and the
acid concentration having a negative effect. The model
defined an optimized single-step FCSPs extraction procedure
for Sargassum sp. (a brown seaweed). A maximal fucose-
containing sulfated polysaccharides yield of ∼7% of the
Sargassum sp. dry matter was achieved by the optimal
extraction procedure of: 0.03 M HCl, 90°C, 4 h. HPAEC-
PAD analysis confirmed that fucose, galactose, and glucur-
onic acid were the major constituents of the polysaccharides
obtained by the optimized method. Lower polysaccharide
yield, but relatively higher fucose content was obtained with
shorter extraction time. The data also revealed that classical
multi-step extraction with acid ≥0.2 M HCl at elevated
temperature and extended time had a detrimental effect on
the FCSPs yield as this treatment apparently disrupted the
structural integrity of the polymer and evidently caused
degradation of the carbohydrate chains built up of fucose
residues.
Keywords Fucoidan . Sargassum . Brown seaweed .
Fucose . Bioactive compound . Extraction method
Introduction
Fucose-containing sulfated polysaccharides, or “fucoidan”,
from brown algae may contain differing glycosidic linkages
and are variously substituted with acetate and side branches
containing fucose or other glycosyl units. These fucose-
containing sulfated polysaccharides (FCSPs) can be extracted
from brown seaweed species such as Fucus, Laminaria, and
Sargassum (Li et al. 2008; Mori and Nisizawa 1982). A range
of biological activities have been attributed to FCSPs including
anti-tumoral (Zhuang et al. 1995), anti-viral (Adhikari et al.
2006; Trinchero et al. 2009), anti-inflammatory (Blondin et al.
1994); and notably anticoagulant effects (Nardella et al. 1996).
The potential pharmaceutical and medical applications of
FCSPs have recently directed special interest into utilization
of brown seaweeds as a source of FCSPs (Li et al. 2008;
Cumashi et al. 2007).
Some brown seaweed FCSPs have a backbone of 3-
linked α-L-fucopyranose, while others have a backbone of
alternating 3- and 4-linked α-L-fucopyranose residues and
sulfated galactofucans (Bilan and Usov 2008). The sulfated
galactofucans are prominently found in various Sargassum
species (Duarte et al. 2001; Zhu et al. 2003). These sulfated
galactofucans are mainly built of (1→6)-β-D-galactose
and/or (1→2)-β-D-mannose units with branching points
M. T. Ale :J. D. Mikkelsen :A. S. Meyer (*)
Center for Bioprocess Engineering,
Department of Chemical and Biochemical Engineering,
Technical University of Denmark (DTU),
Søltofts Plads—Building 229,
DK-2800 Kgs. Lyngby, Denmark
e-mail: am@kt.dtu.dk
J Appl Phycol
DOI 10.1007/s10811-011-9690-3

formed by (1→3) and/or (1→4)-α-L-fucose, (1→4)-α-D-
glucuronic acid, terminal β-D-xylose and sometimes (1→
4)-α-D-glucose (Duarte et al. 2001). Early studies also
reported the existence of fucoglucuronans having a back-
bone of glucuronic acid, mannose, and galactose residues
with side chains of neutral and partially sulfated residues
of galactose, xylose, and fucose; these supposed fuco-
glucuronans have been reported to be present in
Sargassum linifolium (Abdel-Fattah et al. 1974).
Extraction of fucose-containing sulfated polysaccharides
from brown seaweeds generally involves multiple, extend-
ed aqueous extractions, usually with hot acid (hydrochloric
acid), and may include calcium addition to promote alginate
precipitation (Chizhov et al. 1999; Marais and Joseleau
2001). It has long been known that extraction time,
temperature, and acid concentration/pH may influence both
yields and composition of the resulting fucoidan or FCSPs
(Li et al. 2008; Black et al. 1952). Already in 1952, Black
et al. (1952) reported how the use of different extraction
methods influenced the quantity of fucose with a disparity
of 20% to 80% of total fucose of Fucus vesiculosus
fucoidan and 20% to 55% of total fucose of Pelvetia
canaliculata fucoidan (Black et al. 1952). The influence of
extraction method on fucose-containing sulfated poly-
saccharides yield is further exemplified by data for the
yield from Laminaria japonica: the yield was only 1.5%
of the dry weight (DW) of the seaweed when extracted
with alkaline solution at 95°C for 2 h (Sakai et al. 2002),
but 2.3% DW when the extraction was done with water in
an autoclave at 120°C for 3 h (Wang et al. 2008). On the
other hand, the FCSPs notably fucoidan yield of a
combined extract of F. evanescens was 12.9% DW when
extracted four times with 2% CaCl2 solution at 85°C for
5 h (Bilan et al. 2002), while cold extraction with 0.4%
HCl at 25°C for 5 h yielded 12.0% DW (Zvyagintseva et
al. 1999). Typically, the maximum FCSPs yields from
(dried) brown seaweeds range from 5–7% DW. Fucoidan
yields extracted from F. vesiculosus have thus been
reported to be 7.0% DW; while the fucoidan yields
obtained from Sargassum horneri and Undaria pinnatifida
were found to be 5.2% DW and 6.8% DW, respectively
(Kuda et al. 2002). Despite the existence of early seminal
studies about FCSPs extraction, notably Black et al.
(1952), that recommended the use of a three-step hot acid
extraction procedure, there is only limited systematic
information about the influences and apparently complex
interactions of extraction parameters acid, temperature and
time on fucose-containing sulfated polysaccharides yield.
Sargassum is an unexploited brown seaweed genus in
the Phaeophyceae which grows wildly in enormous
quantities almost all over the world, but it is particularly
abundant along the coastal regions in south East Asia,
where members of this genus are considered as nuisance
seaweeds. In order to initially assess the possible use of
Sargassum sp. as a source of FCSPs, we wanted to evaluate
systematically the influence of the extraction parameters,
i.e., acid concentration, time, temperature, and maximize
the FCSPs yields, while at the same time attempt a
relatively mild extraction procedure. In this present work,
we therefore systematically examined the effects of
different combinations of acid, reaction time and temperature
on the fucose-containing sulfated polysaccharides yields from
a Sargassum sp. obtained from Vietnam. We also compared
the composition of the extracted polysaccharides obtained by
the final yield-optimized one-step extraction procedure as
well as an analogous two-step extraction procedure to
those obtained with the classical, state-of-the art multi-
step fucoidan extraction methods of Black et al. (1952)
and Bilan et al. (2002).
Materials and methods
Chemicals Hydrochloric acid 37%, D-glucose and
D-xylose were purchased from Merck. Ethanol 99.8%,
trifluoracetic acid 99% (TFA), trichloroacetic acid 99%,
diethyl ether, CaCl2, Na2SO4, BaCl2, L-arabinose,
L-rhamnose, D-galactose, L-fucose, D-mannose and
D-glucuronic acid were from Sigma-Aldrich (Germany).
Agarose D-2 was obtained from Hispanagar (Spain). All
chemicals used were analytical grade. Dried Sargassum
sp. was obtained from the company Viet Delta Co. Ltd.
(Ho Chi Minh City, Vietnam).
Design of experiment Two-step and one-step extraction
experiments were evaluated according to an experimental
design objective of response surface modeling (RSM). A
central composite face centered design was used with
process modeling and optimization using multiple linear
regression modeling. The number of different parameter
combinations in each design was 14 with 3 replications of
the center point. The varying factors were as follows: acid
concentrations, 0, 0.1, and 0.2 M of HCl; extraction
temperatures, 30, 60, and 90°C; and reaction times were
1, 3 and 5 h. All extraction experiments were performed in
duplicate.
General extraction process Sargassum sp. was ground by
milling using an OBH Nordica Coffee Mill 100 watts (OBH
Nordica Denmark A/S, Denmark) to pass through a 500-μm
sieve and pretreated with a MeOH-CHCl3-H2O (4:2:1) mixture
at room temperature to remove colored matter and phenol
compounds prior to extraction. All extractions (Fig. 1a and b)
were done in a water bath (Julabo SW22—Germany) with
shaking at 200 rpm. 20 mL (HCl) of different concentration
(according to the experimental design) were added to a
J Appl Phycol

centrifuge flask that contained 1 g of ground dried, pretreated
Sargassum sp. In the single-step extraction (Fig. 1a), the
seaweed was extracted according to the factorial design
described in the design of experiment. After extraction, the
suspended seaweed was centrifuged at 10,600×g for 5 min, the
supernatant was removed. Then the residue was washed with
5 mL MilliQ water and centrifuged again at 10,600×g for
10 min, thereafter the first supernatant and the supernatant
from the washing were combined (Extract A). A liquid fraction
(16 mL) from Extract A was precipitated with 60% (v/v)
aqueous ethanol to obtain crude FCSPs. The precipitate was
washed once with water and was coagulated immediately with
either 0.5 M NaCl or 1 M CaCl2 to release and precipitate
alginate. The sticky precipitate was discarded and the
supernatant was centrifuged again at 10,600×g for 10 min.
The pellet was collected and transferred to an Eppendorf tube.
Each Eppendorf tube was weighed prior to pellet transfer, and
then centrifuged at 10,600×g for 5 min; the pellet was washed
with alcohol and diethyl ether and then finally dried overnight
at 50°C. The amount of dried crude FCSPs yield was
translated to dry weight (in mg) of the total extract volume
(in mL) from the original dry seaweed solution (in grams dry
weight per milliliter) and the FCSPs yield (in mg g-1
dry
weight) was thus based on the original seaweed dry weight.
For the two-step extraction (Fig. 1b), the seaweed residue of
the single-step extraction (Residue A, Fig. 1b) was extracted
once more by addition of 10 mL HCl (of a concentration
according to the experimental design) and the suspended
seaweed was treated the same way as described above to
obtain Extract B. Extract A and B were then combined, and
crude FCSPs was isolated by the same procedure as described
above (Fig. 1b).
Benchmark experiment A comparative study between the
optimized conditions of the two-step extraction and the
one-step extraction respectively, obtained from the multi-
variate models, and two other extraction conditions from
known methods (Black et al. 1952; Bilan et al. 2002) was
carried out: The Sargassum sp. was pretreated as mentioned
above prior to extraction. The RSM optimized two-step
extraction condition, 0.07 M HCl at 90°C for 3 h (twice),
was designated as Method 1. The RSM optimized one-step
extraction condition, 0.03 M HCl at 90°C for 4 h (once), or
1 h (once), was designated as Method 1a. Method 2 was the
benchmark extraction of Bilan et al. (2002) which, in short,
involved extraction of the ground, dried, pretreated Sargas-
sum sp. four times with a 2% CaCl2 solution at 85°C for 5 h
(Bilan et al. 2002). Method 3 was the benchmark
extraction of Black et al. (1952): for this extraction, the
ground, dried, pretreated Sargassum sp. was extracted
three times with 0.17 M HCl at 70°C for 1 h with washing,
centrifugation and pH reduction from pH 2.5 to 1.9 after
each extraction step (Black et al. 1952). After extraction,
all extracts were precipitated with ethanol, washed with
H2O and treated with 1 M CaCl2 to precipitate alginate. In
each case, the supernatant was then centrifuged, precipi-
tated with ethanol, centrifuged again, and the pellet was
dried overnight at 50°C.
Dry Milled Alga
Dilute acid extraction: 0.1 M & 0.2 M HCl
Reaction time: 1 h, 3 h, 5 h
Temperature: 30, 60, 90 °C
Extract A Residue A
Extract B
Residue B
Extract A+B
EtOH
Supernatant
Precipitate
Dry Milled Alga
Extract A Residue A
EtOH
precipitation
EtOH
Supernatant
Precipitate
Coagulation
Washing and drying
Fucose-containing
sulfated polysaccharides
ba
EtOH
precipitation
Coagulation
Washing and drying
Fucose-containing
sulfated polysaccharides
Fig. 1 Schematic diagram of a single-step (a) and two-step extraction (b) of fucose-containing sulfated polysaccharides from Sargassum sp.
J Appl Phycol

Acid hydrolysis Dried Sargassum sp. powder and extracted
polysaccharide samples (50 mg) were subjected to acid
hydrolysis using 2 M TFA at 121°C for 2 h (Arnous and
Meyer 2008). After hydrolysis, the mixture was freeze
dried, and the dried powder was resolubilized and centri-
fuged at 10,000×g for 10 min to collect the supernatant
then filtered using a 0.2 μm syringe tip filter (Sun Sr. USA)
prior to HPAEC-PAD analysis (see below). The monosac-
charide recoveries were determined for arabinose, rham-
nose, fucose, galactose, glucose, xylose, and glucuronic
acid and used as correction factors for the quantitative
monosaccharide assessment principally as described
previously (Arnous and Meyer 2008).
Compositional analysis The separation and quantification
of monosaccharides of the acid hydrolyzed polysacchar-
ides were done by HPAEC-PAD using a BioLC system
consisting of GS50 gradients pumps/ED50 electrochem-
ical detector/AS50 chromatography compartment coupled
to an AS50 autosampler (Dionex Corp., USA). Separa-
tions were performed using a CarboPacTM PA20
(3 mm×150 mm) analytical column (Dionex Corp.)
according to Thomassen and Meyer (2010). The quanti-
fication was carried out using the external monosaccharide
standards: L-arabinose, L-rhamnose, L-fucose, D-galactose,
D-glucose, D-mannose, D-xylose and D-glucuronic acid.
Data were collected and analyzed with Chromeleon 6.80
SP4 Build 2361 software (Dionex Corp.). The sulfate
analysis was performed by a turbidometric method using
agarose-barium reagent as described by Jackson and
McCandless (1978).
Statistical and data analysis The analyses of variances
were performed using Minitab 15 (Minitab, Inc., UK) with
a significance value of P≤0.05. The program Modde
version 7.0.0.1 (Umetrics AB, Sweden) was used as an
aid for the design of experimental templates and for the
evaluation of the effects and the interactions by multiple
linear regression analysis.
Results
Polysaccharide compositional profile
The HPAEC analysis of the TFA hydrolysate of Sargassum
sp. showed that the polysaccharide profile was dominated
by fucose (29±3.7), galactose (14±2.1), and glucuronic
acid (39±3.5)mg·g−1
seaweed dry weight, with a sulfate
content of (155±5)mg·g−1
seaweed dry weight, while other
minor components such as mannose, rhamnose, glucose,
arabinose, and xylose were also detected (data not shown).
This composition is in accordance with early studies of
sulfated polysaccharides from S. linifolium (Abdel-Fattah et
al. 1974) and typical for the Sargassaceae.
Evaluation of extraction—two steps
Optimizing two-step extraction To determine the optimal
extraction of fucose-containing sulfated polysaccharides,
the seaweed was extracted twice and the effects of different
treatment factors were tested systematically, i.e., acid, 0 to
0.2 M HCl; temperature, 30 to 90°C; and time, 1 to 5 h
(Fig. 1b). According to the model, the predicted maximum
yield of 7.1% DW, was achieved using 0.07 M HCl/90°C/3 h
extracted twice. The predicted extraction yield obtained when
the two-step extraction was done without acid, at 30°C for 1 h
produced 2.9±0.8% DW only, while the harshest extraction
treatment of 0.2 M/90°C/5 h resulted in a yield of 3.1±0.6%
DW from the combined Extract A and B, respectively.
Benchmarking Assessment of the optimal parameters
obtained from the model was carried out by performing
another extraction experiment using the optimum of the
response surface model. Subsequently, a comparative
extraction study was also done to verify the feasibility of
the model. Two extraction methods were compared to the
predicted optimal extraction condition: Method 1 was the
predicted maximum optimal condition (i.e., 0.07 M HCl,
90°C, and 3 h-two-step extraction); Method 2 was as
described by Bilan et al. (2002); and Method 3 was as
described by Black et al. (1952). The data showed that the
total yields obtained by Method 1 were higher than
predicted by the model, namely ∼8.5% DW, and that the
total polysaccharide yields with the two-step extractions
Method 1 and 2 were similar, but much higher than what
was obtained with Method 3 (∼5% DW; Fig. 2). The data
also showed that the major part of the yield was obtained
during the first extraction. The results of these experiments
Fig. 2 Polysaccharide yield (% DW) of Sargassum sp. extracted
using different methods. Method 1 was extracted using 0.07 M HCl/
90°C/3 h (two-step); Method 2 as described by Bilan et al. (2002) and
Method 3 as described by Black et al. (1952)
J Appl Phycol

thus showed that the yield of the first extraction (Extract A)
of Method 1 (7.6±0.31% DW) was higher, p<0.05, than
the corresponding yields of the benchmark methods
Method 2 (6.2±0.08% DW) and Method 3 (4.2±0.09%
DW), respectively (Fig. 2). Based on this result, it was
decided to evaluate whether a higher polysaccharide yield
could be obtained using only a single-step extraction of
Method 1 type. A second statistical experiment was
therefore performed to define the optimum acid concentra-
tion, temperature and incubation time for this single-step
extraction (Fig. 1a, Extract A only).
Optimization of polysaccharide yield—single-step
extraction
Multiple linear regression analysis of the data obtained in the
statistically designed single-step extraction study showed that
an increase in extraction time and temperature significantly
increased the polysaccharide yield, whereas a decrease of acid
concentration also significantly increased the yield (Table 1).
Moreover, acid and acid interaction, acid and time interac-
tion and acid and temperature interaction each had a
significant effect on the polysaccharide yield (Table 1).
According to the model, the maximum polysaccharide yield
of ∼8% DW from Sargassum sp. would be obtained at
0.03 M HCl/90°C/4 h, whereas the lowest polysaccharide
yield was at 30°C or 60°C with 0.2 M HCl (Fig. 3).
The quality of the model was confirmed by the average
value of the center points (5.76±1.01%DW) being close to
the coefficient of the constant (6.28±0.29%DW). The
regression model was given as y=6.28−1.17 x1+0.23 x2+
0.63 x3−1.46 x1 x1−0.35 x2 x2+0.31 x3 x3−0.36 x1 x2−
0.51 x1 x3−0.06 x2 x3 (x1 is acid concentration; x2 is time;
x3 is temperature; Table 1). The summary of the fit and the
predictability of the model for FCSPs yield were satisfac-
tory with R2
=0.928; Q2
=0.853, model validity=0.891;
and model reproducibility=0.889 (Fig. 3).
Plots of the polysaccharide yields and fucose contents
obtained in response to extraction time and temperature
further illustrated the effects of the different treatment
factors during single-step extraction (Fig. 4). With no acid
treatment, the yield of polysaccharide rose when extraction
time and temperature increased, while high acid treatment
(0.2 M HCl) gave low yield with no significant differences
with elevated time and temperature (Fig 4a). After each of
the different extraction treatments of the Sargassum sp.
seaweed, the recovered polysaccharide was sequestered and
subjected to TFA hydrolysis and thereafter HPAEC to
analyze the monomer content. The results showed that
the fucose content was higher in the polysaccharide
extracted with 0.2 M HCl than without acid when the
treatment time was 1 or 3 h, but at 90°C/5 h, the fucose
level was higher with no acid than with 0.2 M HCl
(Fig. 4b). The influence of acid treatment (0.2 M HCl)
during extraction was thus observed to have a negative
effect on the fucose content when time and temperature
were elevated (Fig. 4b).
Comparative extraction analysis
The optimal condition of the single-step extraction pre-
dicted by the model (i.e., 0.03 M HCl/90°C/4 h) was used
in an actual extraction experiment designated as Method 1a
for comparative analysis of the monosaccharide composi-
tion with the benchmark extraction methods of Bilan et al.
(2002): Method 2 and Black et al. (1952): Method 3. The
monosaccharide composition of the polysaccharide showed
that fucose, galactose, and glucuronic acid were the
dominant monomers (Table 2). Clearly, the fucose content
of the statistically optimized one-step extraction method
was significantly higher than the fucose levels in the
fucoidan (or FCSPs) obtained by both Method 2 and 3
(Table 2). Method 2 had the lowest glucuronic acid content
among the three methods (Table 2); this was probably due
to the interaction of CaCl2 after each round of extraction.
The sulfate content of the fucoidan polysaccharide was
however lower with the optimized one-step 4-h extraction
than that obtained in Method 2 and 3.
Investigation of extended extraction time
Based on the predicted optimized extraction model (Fig. 3)
and the raw data (Fig. 4), it was decided to evaluate the
influence of extended extraction time on the extracted
polysaccharide composition. Extended extraction was car-
ried out for up to 46 h using the predicted one-step optimal
Table 1 Multiple linear regression results of the parameters and
interactions on the polysaccharide yield using the single-step
extraction
Parameters and interactions % DW
Coefficient P values
Acid (x1) −1.17 3.46×10−10
Time (x2) 0.23 0.045
Temperature (x3) 0.63 7.11×10−6
Acid×acid −1.46 1.96×10−7
Time×time −0.35 No effect
Temperature×temperature 0.31 No effect
Acid×time −0.36 0.006
Acid×temperature −0.51 0.0004
Time×temperature −0.06 No effect
Constant 6.28 2.56×10−22
J Appl Phycol

treatment, i.e., 0.03 M HCl/90°C. The duration of
extraction time influenced the polysaccharide yield
(Fig. 5a). Hence, the total polysaccharide yield increased
until 8 h of extraction (using 0.03 M HCl/90°C) and the
yield then reached a plateau of approximately 9% DW
(Fig. 5a). The amount of fucose dropped steadily as the
duration of the extraction time increased whereas glucur-
onic acid increased (Fig. 5a). Apparently, the duration of
extraction time also resulted in an almost linear increase in
the mannose and galactose content of the extracted
polysaccharide, but did not affect the xylose, glucose,
and rhamnose contents (Fig. 5b). In addition, the extended
extraction time significantly decreased the sulfate content
until 8 h of extraction (Fig. 5b). These results indicated
that obtaining a high yield of a fucose-rich fucans from
Sargassum sp. having a limited glucuronic acid (and
galactose and mannose) content was a compromise, and
the data confirmed that an extraction time of 3 h was the
best compromise to achieve high yields and a high fucose
level (Fig. 5a). It is tempting to speculate that some “true”
fucoidan is released in the early minutes of the extraction,
that the acid catalyzed loss of α-fucosyl linkages relative
to the other glycosidic bonds during extended treatment
may confound the picture. One could interpret the
evidence as indicating that the product isolated contained
a sulfated fucose-containing heteroglycan, possibly having
a glucuronan primary structure with extensive fucosyl side
branches which are cleaved and lost as extraction time is
extended. A sulfated fucan (a fucoidan) may occur in
Sargassum sp., but further elucidation of fucose-
containing sulfated polysaccharides from Sargassum sp.
is required. With a lower total polysaccharide yield
requirement, a relatively higher fucose content could be
obtained with a shorter extraction of 1 h as compared to a
4 h extraction (Table 2 and Fig. 5).
Discussion
Statistically designed optimization of FCSPs extraction was
conducted to produce a model that provided an understand-
ing of the complex influences and interactions of the
extraction factors temperature, time, and acid concentration,
and in turn allowed prediction of the optimal extraction
treatment to obtain high FCSPs yield. The model predicted
that 0.07 M HCl/90°C/3 h produced high FCSPs yield
using two-step extractions. However, careful assessment of
the data obtained after the first and second steps at these
optimal extraction conditions showed that an additional
extraction step to produce Extract B (Fig. 1b) could be
omitted since its yield was very low compared to Extract A
(Fig. 2). Hence, a new optimized extraction design was
performed for a single-step extraction using the same
factors settings, i.e., acid, 0 to 0.2 M HCl; temperature,
30 to 90°C; and time, 1 to 5 h. The maximum yield
produced by this new optimal condition (0.03 M HCl/90°C/
4 h) was ∼7.0% DW. Previously reported multi-step
extraction results of fucose-containing polysaccharides
from S. horneri and U. pinnatifida were 5.17% DW and
6.77–15.10% DW (Kuda et al. 2002); from S. ring-
goldianum it was 200 mg from fresh 150 g algal fronds,
approximately equivalent to 0.67% DW (Mori and Nisizawa
1982). Hence, the result of multiple linear regressions of the
parameters and interaction on the fucose-containing poly-
Fig. 3 The 3D response surface plots at three different temperatures
each at the optimal extraction condition and maximum fucose-
containing polysaccharide yield (% DW) of the single-step extraction
procedure as a function of time (h) and HCl concentration (M). R2
=
0.928; Q2
=0.853; model validity=0.891; model reproducibility=
0.889 respectively
J Appl Phycol

saccharide yield for the one-step extraction was in agreement
with the available data.
The composition obtained from HPAEC-PAD analysis of
the TFA hydrolysate of Sargassum sp. agrees with the
prevalent polysaccharide structure among Sargassum
species; hence, in the case of S. patens and S. stenophyl-
lum (Duarte et al. 2001; Zhu et al. 2003) the structure has
been found to be a linear backbone of (1→6)-β-D-
galactose and/or (1→2)-β-D-mannose units with branched
chains formed by (1→3) and/or (1→4)-α-L-fucose, (1→4)-
α-D-glucuronic acid, terminal β-D-xylose and sometimes
(1→4)-α-D-glucose. However, as pointed out by Percival
and McDowell (1967): "Fucoidin, first isolated and named
by Kylin (1913) was more systematically named fucoidan".
The algal source in this case was F. vesiculosus, and the
Kylin product has been established as a fucan sulfate
(currently termed fucoidan as it was isolated from brown
seaweed). Percival and McDowell understood and empha-
sized that fucoidan referred to polysaccharides consisting
almost entirely of fucose and ester sulfate. Fucose-containing
heteropolysaccharides (e.g., glucuronoxylofucans) were trea-
ted as quite different entities from fucoidan. Painter (1983)
provided the following definition: "Natural polysaccharides
built up essentially of sulfated α-L-fucose residues are
known as fucoidans". This working definition of fucoidan
has been retained by polysaccharide chemists to the present
(Mabeau et al. 1990; Chevolot et al. 1999; Berteau and
Mulloy 2003).
The optimization of the one-step method illustrated that
a single-step extraction with the combination of low acid
concentration, 0.03 M HCl or below, and temperature near
90°C was sufficient to produce a satisfactory FCSPs
(fucoidan) yield. The integrity of the polysaccharide was
best conserved at low acid treatment (Fig. 4b), since the use
of 0.2 M HCl apparently broke the integrity of the
polysaccharide molecules resulting in a decline of fucose
at elevated time and temperature (Fig. 4b). This indicated
that the higher acid levels might have caused a loosening of
the cell wall matrix allowing local penetration of the acid
into the fucoidan in the intercellular spaces resulting in
partial degradation of FCSPs or notably fucoidan (Kloareg
1984; Mabeau et al. 1990). The effect of acid might have
been enhanced as dried seaweed material was used in the
experiment, where it can absorb and expand abruptly
during hydration (Phillips et al. 2002). The degradation of
carbohydrate chains built up of fucose was recognized
when the duration of extraction time increased (Fig. 5). Our
result is in agreement with Ponce et al. (2003) who reported
that longer extraction time led to poorer fucose content. In
Table 2 Analysis of monosaccharide after 2 M TFA hydrolysis of the
sulfated polysaccharide fractions of Sargassum sp. isolated by
different extraction methods
Monomers
(mg/g DW)
Method 1a
(1 step—1 h)
Method 1a
(1 step—4 h)
Method 2 Method 3
Fucose 113±0.9 97±2 49.2±1.7 54.8±1.7
Rhamnose 6.2±0.6 2.9±0.3 6.29±0.07 nd
Galactose 39±6 39 ±1.9 25.8±0.30 36±1.34
Glucose 11.1±0.2 3.7±0.4 10.9±0.13 13.7±1.25
Mannose 11.3±1.6 11.1±1.7 2.41±0.03 5.76±0.21
Xylose 15.7±1.1 11.4±1.4 5.12±2.36 6.8±1.7
Gluc Acid 85±11.7 97±2.7 10.0±0.12 45±5.8
Sulfate 362±16.5 308±11 341±5.2 327±8.5
Data given as average values±standard deviation, n=3. Method 1a
extraction by using the optimized model of the one-step extraction
(0.03 M HCl/90°C) with an extraction time of either 1 h or 4 h as
indicated. Method 2 as described by Bilan et al. (2002), and Method 3
as described by Black et al. (1952). General linear model significantly
different (P<0.05)
Temperature [°C]
Polysaccharideyield[%DW]
2
4
6
8
10
0 M HCl
0.2 M HCl
Time [h]
30 60 90
1 3 5
Fucose[mg/gDWPolysaccharide]
0
2
4
6
8
10
12
14
16
18
0 M HCl
0.2 M HCl
Fig. 4 Polysaccharide yield (a) and fucose content (b) of different
combination of extraction treatment (i.e., acid, time and temperature)
of fucose-containing polysaccharide seaweed (Sargassum sp.). Data
given as mean±SD, n=3
J Appl Phycol

addition, longer extraction time at higher temperatures led
to higher polysaccharide yield with lower amount of sulfate
and higher proportion of glucuronic acid (Ponce et al. 2003;
Duarte et al. 2001). The same trend was also noticed in our
present work. The glucuronic acid increased while sulfate
decreased with time, i.e., the sulfate content was highest
when glucuronic acid was lowest (Fig. 5a, b). This was also
observed for fucoidan extraction from S. ringgoldianum
(Mori and Nisizawa 1982).
In conclusion, a simple and practical method for
recovering a suite of complex fucose-containing sulfated
polysaccharides from Sargassum sp., has been established.
Clearly, yield and chemical composition of the product are
strongly affected by the method of extraction as was to be
expected. The yield data are gravimetric only and so pertain
to a crude mixture of biopolymers extracted. The evidence
presented shows that the extracted polysaccharide product
is heterogeneous at any time it is analyzed, although the
composition varies with the duration of extraction. The
monomeric composition shows that fucose and sulfate were
important components of the polysaccharide mixture as
isolated. An optimized one-step extraction treatment to
obtain high yields of a fucose-containing sulfated polysac-
charide from Sargassum sp. was developed, and the effect
of different treatment parameters on the integrity of the
polysaccharide was established. The results confirmed that
Sargassum sp. may be a good source of fucose-containing
sulfated polysaccharides. The data also demonstrated the
vulnerability of fucose-containing sulfated polysaccharides
to harsh extraction conditions and confirmed that the
extraction method significantly influences the yields and
not least the polysaccharide composition of the extracted
polysaccharide. Furthermore, the main conclusions confirm
the long known facts that cell wall polymers of brown algae
are complex, and that the yields and chemical nature of
polysaccharides recovered from such seaweeds are mark-
edly influenced by the conditions used to extract them. It is
important to emphasize this point as it has a major bearing
on any study in which such products are being evaluated
for biological activity. It is our belief that the model
obtained may be applied to other FCSPs or fucoidan-
containing types of brown seaweed.
PolysaccharideYield[%DW]
0
2
4
6
8
10
12
Fucose[mg/gDW]
40
60
80
100
120
140
GlucuronicAcid[mg/gDW]
100
150
200
250
300Polysaccharide Yield
Fucose
Glucuronic Acid
Extraction Time [h]
0 10 20 30 40 50
Gal,Man,Xyl,Glu,Rham[mg/gDW]
0
20
40
60
80
Sulfate[mg/gDW]
50
100
150
200
250
300
350
400
Galactose
Mannose
Xylose
Glucose
Rhamnose
Sulfate
a
b
Fig. 5 Polysaccharide yield and
monosaccharide content as a
result of prolonged reaction time
using the predicted optimized
one-step extraction condition
0.03 M HCl/90°C. a Polysac-
charide yield, fucose and
glucuronic acid, b galactose,
mannose, xylose, glucose,
rhamnose and sulfate
J Appl Phycol

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