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Research Article
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Biochemical Composition and Fatty Acid Profile of the Green Alga Ulva reticulata
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Annian Shanmugam
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Chendur Palpandi
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ABSTRACT
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The total lipid, protein, carbohydrate, water and fatty acid contents
of seaweed U. reticulata belonging to the class of Chlorophyceae
that had been collected from Vellar estuary, southeast coast of India.
Water contents of the U. reticulata was found as 75.33%. Carbohydrate,
protein and lipid contents have been estimated as 50.248, 8.484, 19.98
and 1.7% of the dry sample correspondingly. The analysis of fatty acids
by gas chromatography revealed the presence of myristic acid, palmitic
acid, heptadecenoic acid, oleic acid and linoleic acid. Among the fatty
acids, palmitic acid was predominant in all the fatty acids studied.
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INTRODUCTION
Seaweeds have been used since ancient times as food, fodder and fertilizer
and as source of medicinal drugs. Today seaweeds are the raw material
for industrial production of agar, carrageenan and alginates (Barbara
and Cremades, 1993), but their consumption as food in Asian countries
are still going on (Mishra et al., 1993). They are nutritionally
valuable as fresh or dried vegetables, or as ingredients in a wide variety
of prepared foods (Robledo and Pelegrin, 1997). In particular, certain
edible seaweeds contain significant quantities of lipids, protein, vitamins
and minerals (Norziah and Ching, 2000; Sanchez-Machado et al.,
2002; Wong and Cheung, 2000), although nutrient contents vary with species,
geographical location, season and temperature (Dawes et al., 1993;
Kaehler and Kennish, 1996).
The study of natural products and the chemical constituents occurring
in algae is known as phycochemistry. Usually the natural products are
the secondary metabolites. The metabolic behaviour of lipids is largely
determined by the structure of the component fatty acids. Generally, fatty
acids occurring in algal lipids are straight chain, even carbon number
molecules and usually contain one or more double bonds. Much work has
been done fatty acid composition of microalgae and seaweeds (Marolia et
al., 1982; Takagi et al., 1985; Wood, 1988; Liekenjie, 1989).
However, information on the fatty acids of seaweeds collected from Parangipettai
coast is lacking. The objective of this study was to determine the biochemical
composition and fatty acid profile of the green alga U. reticulata
originating from Vellar estuary, Parangipettai coast.
MATERIALS AND METHODS
Seaweed was collected from Vellar estuary, during low tide. Samples has
been cleaned from epiphytes, epifauna, pebbles and other molluscan shells
and washed several times in fresh water, blotted and weighed.
The fresh samples were dried at 60°C for 24 h (in hot air oven) and
the dried powder was sieved to get fine powder. Total protein was estimated
by following the method described by Raymont et al. (1964), total
carbohydrate using phenol sulphuric method (Dubois et al., 1956)
and total lipid was extracted by Folch et al. (1956) using chloroform:
methanol mixture. The moisture content was estimated by subtracting the
dry weight from the known wet weight of the sample. Protein, carbohydrate
and lipid content of the species of U. reticulata were analyzed
and expressed in percentage. An extraction procedure for fatty acid was
followed as described by Bligh and Dyer (1959). Identification and quantification
of fatty acids were done using Agilent Technologies 6890 N, Network GC
system.
RESULTS AND DISCUSSION
Lipids, proteins and carbohydrates are the most important biochemical
components in algal biomass. Lipids are rich in -C = O- bonds, providing
much more energy in oxidation processes than other biological compounds.
Mainly owing to their high reduction levels, they constitute a convenient
storage material for living organisms. In algae, the lipids are widely
distributed, specially in several resistance stages (Miller, 1962).
Carbohydrate is the most important component for metabolism and it supplies
the energy needed for respiration and other metabolic processes. In the
present experiment the carbohydrate content of U. reticulata was
found as 50.248% (Fig. 1). The findings of the present
experiment coincide well with that of carbohydrate contents reported by
the earlier studies like Reeta and Kulandaivelu (1999). They found that
the carbohydrate contents were 48.4% of Gracilaria spp. in dry
weight basis. Hossain et al. (2003) reported that the carbohydrate
contents were 19.93 and 20.81% in sample 1 and 2 from Sargassum horneri.
Reeta (1993) has studied the carbohydrate content varied from 6.65 in
March to 15.18 in January in S. wightii. Haroon (2000) investigated
the carbohydrate contents were 54.71±8.17% of DW in Enteromorpha
spp. Sasikumar (2000) studied the two species of green algae Enteromorpha
intestinalis and C. linum, the carbohydrate contents were 20.4
to 54.6%. The highest average total carbohydrate contents from U. rigida
(Chlorophyta) was 63.04±29.15 kg-1
D.W (6.3%) (Dere et al., 2003). Whereas in the present investigation
the carbohydrate contents was reported as 50.248% which is higher than
that of S. wightii and lower than that of the others such as Enteromorpha
spp., C. linum and U. rigida. Lipids and carbohydrate
contents should obviously be very variable depending upon the state of
nutrition of cells (Ricketts, 1966).
Protein are having crucial functions in
all the biological processes. Their activities can be described by enzymatic
catalysis, transport and storage, mechanical sustentation, growth and
cellular differentiation control (Stryer, 1988). In the present study
the protein content was estimated as 19.98% in U. reticulata (Fig.
1). The findings of the present experiment coincide well with
the protein contents reported by Sasikumar (2000) who has reported the
varying protein content between 5.2 and 18.6% in Enteromorpha intestinalis
and C. linum. Dere et al. (2003) observed the maximum protein
content (0.94 to 31.03%) in some of the Rhodophyta and some green seaweeds
belonging to the genus Ulva, the content was ranging between 2.9
and 28.1%. Burtin (2003) investigated the higher protein contents in green
and red seaweeds (on an average of 10-30% of the dry weight). Hossain
et al. (2003) reported the protein content of 22.38 and 21.96%
of dry sample 1 and 2 from S. hornei. Roslin (2003) calculated
the protein content in Chlorophyceae and found varying varied from 1.5
to 24.8%. In Phaeophyceae, the maximum protein content was shown by S.
ilicifolium (28.2%) and S. wightii (28.2%). In the present
study the protein contents were higher than that of the earlier studies
like Haroon (2000) i.e., the protein content of Enteromorpha spp.
showed the minimum of 9.42±4.62% and maximum of 20.60±5.00%
on dry weight basis.
In general the total lipid content was
always found less than 4% (Herbreteau et al., 1997) in almost all
the seaweeds studied so far. Falling in the same line the lipid content
in U. reticulata was also reported as 1.7% (Fig.
1). This general trend is further supported by the findings of Reeta
(1993) in S. wightii (0.159 to 1.551%), Reeta and Kulandaivelu
(1994) in Gracilaria spp. (0.78 to 3.97%) and Sasikumar (2000)
in Enteromorpha intestinalis and C. linum (1.2 to 8.6%).
Hossain et al. (2003) also reported 1.38 and 1.96% of Glycolipid
in samples 1 and 2 of S. horneri.
Water is biologically significant as an
essential metabolite i.e., it participates in the chemical reactions of
metabolism. In particular it is used as a source of hydrogen ion in photosynthesis
and is used in hydrolysis reactions. In the present study the moisture
contents were 75.33% in U. reticulata (Fig. 1).
This result is in conformity with the observation of Hossain
et al. (2003) where the moisture contents were found as 86.94%
in sample -1 and 87.0% in sample-2 from S. horneri.
Lipid represent only 1-5% of algal dry
matter and show an interesting polyunsaturated fatty acid composition
particularly omega 3 and omega 6 acids which play a role in the prevention
of cardio-vascular diseases, osteoarthritis and diabetes. The green algae
show interesting levels of alpha linolenic acid (ω3 C 18:3) (Burtin,
2003).
Although seaweeds are not a conventional
source of energy (their total lipid content is low), their polyunsaturated
fatty acids contents are high when compared to terrestrial vegetable (Darcy-Vrillon,
1993). In the present study saturated fatty acids were dominating (70.01%)
the other groups of fatty acids among the total fatty acids and the individual
contribution of 16:0 and 14:0 was found as 50.76% and 11.77%, respectively
(Table 1). These results are in conforming with the
previous reports (Venkatesalu et al., 2003a, b, 2004; Vasanthi
et al., 2003). The highest relative percentage of palmitic acid
(85.35%) was recorded in Gellidium micropterum (Venkatesalu
et al., 2004). The single most abundant fatty acid C16:0 (which
in Porphyra spp. accounted for 63.19% of all fatty acid) and (Sanchez-Machado
et al., 2004). Palmitic acid was reported as a major fatty acid
common to Ergrezia menziesii, Chondracanthus canaliculatus
and Ulva lobata (Nelson et al., 2002). The highest
relative percentage of myristic acid (7.86) was recorded in Acanthophora
spicifera and the highest relative percentage of pantedecanoic acid
(1.29) was recorded in Padina tetrastromatica (Venkatesalu et
al. 2004). In the present study the myristic acid was recorded in
11.77% and pantedecanoic acid was not recorded.
Table 1: |
Fatty acid profile (% of total fatty
acids) from U. reticulate |
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The monounsaturated fatty acids (MUFA)
were the next most common fatty acids (12.07%) with the higher levels
of mostly 18:1ω7c (6.77%). The findings of the present experiment
coincide well with the earlier study by Dawczynski (2006) the concentrations
of oleic acid were at high levels in Porphyra spp. From China and
Laminaria spp. and accounted for more than 20% of total FAME but
such a high content was only found in single samples. Furthermore, seaweed
varieties tested has low levels of palmitoleic acid (16:1n-7) and the
concentrations of this FA ranged from 0.1 to 3.6% of total FAME.
The polyunsaturated fatty acids occupying
the third position by contributing 7.96% of total fatty acids that are
mainly represented by 18:2ω6c (4.54%). In the previous study by Hossian
et al. (2003) reported that the saturated fatty acids 16:0 and
22:0 and monounsaturated fatty acid 18:1 were the major fatty acids for
simple lipids.
In India, development of novel foods such
as functional foods could be a new possibility for the use of this alga
U. reticulata, especially for the protein-rich species, in human
nutrition. In general, the lipid contents of all edible seaweeds were
low and high levels of polyunsaturated fatty acids of the omega-3 and
omega-6 families. This investigation of edible macroalga U. reticulata
verified the presence of several health-promoting and beneficial nutrients,
such as EAAs, important FAs and highly proteins and low levels of lipids.
Further experimentation should be conducted with the samples of all seasons
through a year for getting biochemical variation in a year.
ACKNOWLEDGMENT
Authors are thankful to the Director,
CAS in Marine Biology and authorities of Annamalai University for providing
with necessary facilities. The authors are also thankful to the Ministry
of Environment and Forests, New Delhi for the financial assistance.
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