Last updated: August 16, 2019
Topic: Food
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important resource for the maintenance of life for ages is by natural products.
The plants are the important resources for preparing life-saving drugs. The
enduring importance of natural products 25% of prescribed pharmaceuticals are
derived from plants. In between 1983 Cragg et al., 1997 reported that
the FDA approved 78% of the new drugs which were derived from unmodified
natural products or from natural sources. In total the half of the global
biodiversity is considered with the large-scale screening of marine species in
development of new drugs (Xu et al., 2004). Marine species are a rich in
structurally novel and biologically active metabolites (Borowitzka and
Borowitzka, 1992; Ely et al., 2004). The primary or secondary
metabolites produced by these organisms are potentially bioactive compounds
which are used in the pharmaceutical industry.

There are
13 genera and 58 species of seagrasses available all over the world. Of these,
six genera are mostly restricted to temperate seas (Amphibolis, Phyllospadi,
Heterzostera, Pseudalthenia, Posidonia and Zostera) and the remaining seven
genera (Cymodocea, Halodule, Enhalus, Halophila, Thalassia, Syringodium and
Thalassodendeon) are distributed in tropical seas. In India, few reports
are available regarding seagrasses (Lakshmanan, 1985, Velusamy and Kannan,
1985, Den Hartog and Yang, 1988., Lakshmanan et al., 1988, Parthasarathy
et al., 1988a., Parthasarathy et al., 1988b; Den Hartog, 1989.,
Ramamurthy et al., 1989, Ravikumar and Ganesan, 1990).

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1991 surveyed the composition of seagrasses and marine algae from India,
Lakshadweep, and Andaman Islands. The seagrass ecosystems from other regions of
the world are described by Hartog, 1970; Hartog, 1977; Jacobs, 1982; Menez et
al., 1983; Brouns, 1986; Larkum and Den Hartog, 1989.

1974 screened the three species of seagrasses against bacterial pathogens. The
result indicated that the lipid and water-soluble phenolic extracts of both
root-rhizome and leaf fractions of H. pinifolia showed best
antibacterial activity against all the nine pathogens tested.

and Pesando, 1988 studied and reported that the aqueous and lipid extracts from
the rhizomes of P. oceanica were found to be active against selected
Gram positive and Gram negative bacteria, dermatophytes, and the yeasts along
with the antileishmanial activity                 (Orhan et al., 2006).  Devi et al., (1997) reported that the
seagrass H. pinifolia showed nil inhibitory activity against any of the
bacterial strains tested. The moderate to high activity of acetone, ethanol and
methanol extracts of Euglena viridis was examined against virulent
pathogens like A. hydrophila, V. anguillarum, P. florescence and E.
coli Das et al., (2008). Numerous studies have been reported
over the last 50 years, on the antimicrobial activities of extracts from marine
plants against biologically important microorganisms. Kim and Lee, (2008)
showed strong antibacterial activities of methanolic extracts of Esiena
bicyclis (B32) and Sargassum spp. (B36) against
Methicillin-resistant Staphylococcus aureus (MRSA), Vibrio
parahemolyticus and Edward tarda.

Howayda et
al., (2007) reported that the ethanolic extract of R. cirrhosa which
inhibited all of the tested bacterial isolates except E.coli.  Kolanjinathan and Stella (2009) indicated
that acetone was the best solution for extracting effective antimicrobial
materials from Sargassum myricystum, Hypnea musiformis, Turbinaria
conoides, Halimedia gracilis and Gracilaria edulis whereas,
Karthikaidevi et al., (2009) used seven different solvents such as ethyl
acetate and methanol for extraction of antibacterial substances from Ulva
reticulate, Codium adherens and Halimeda tuna. Earlier reports
showed that marine plants showed antimicrobial activity against fish pathogens
(Dhayanithi et al., 2010; Anitha, 2006). The MIC of Zostera marina extracts
were ranged from 161mg to 8 mg/ml was active against all three human skin
pathogens Han Gil et al., (2009). They also reported the MIC of the
n-butanol and ethyl acetate fractions were the same with 1 mg/ml against C.
albicans and S. aureus.

et al., (2009) and Ragupathi et al., (2010b) reported the
seagrass Halodule pinifolia showed stong antibacterial activity against
pathogens. Sundaram et al., (2011a) demonstrated that antibacterial
activity of seagrass S. isoetifolium root extracts against fish
pathogens. The broad spectrum of six fractions from acetone extract and one
fraction from hexane root extracts ofC. serrulata exhibited
antibacterial activity (Sundaram et al., 2011b). The methanol extract of
H. ovalis collected from the Chunnambar estuary in Pondicherry exhibited
stong antibacterial activity of 17nm against B. cereus followed by 14nm
against A. baumannii Yuvaraj et al., (2011).

The crude
ethyl acetate extract of E. acorodies collected from the seagrass bed in
Merambung Island inhibited the growth of all test bacteria with the largest
zone of inhibition displayed by P. aeruginosa which was followed by MSSA,
MRSA and S. epidermidis(Mohd et al., 2012). Aswathi et al., (2012b)
reported that the ethanol extraction of the sea grasses C. rotundata showed
better zone of inhibition than other tested extracts against bacterial

Seagrass are marine plants found near
shore waters. They are one of the most highly productive tropical ecosystems
and act as shelter and food for near shore fisheries, marine reptiles and manmals.
They have a widespread distribution that encompasses every continent, except
Antarctica but the highest diversity of seagrass species is centred in the
tropical Indo-Pacific (Waycott et al., 2004). Seagrass habitats
are an important component of the marine environment, providing vital services
such as nutrient cycling, food provision, and climate change mitigation (Orth et
al., 2006; Waycott et al., 2009).
Similar to other marine ecosystems, seagrass habitats are under threat from
human activities, such as coastal development and increased nutrient input.
These impacts have brought about accelerated decline in seagrass habitats
globally (Waycott et al., 2009).

Seagrasses are marine flowering plants that
have the ability to complete their life cycle while fully submerged in marine
environment constraints. Short et al., (2001) reported that
these marine plants cover large geographic area worldwide. Seagrasses provide
services and goods for their ecological conmunity, for example, wave
protection, reduced water flow, fishing ground, and oxygen production (Bail, 2005) and (Aziz et al., 2006).

Ahmad-Kamil et
al. (2013) studied and reported that seagrass
percentage increased during the El-Nino period, due to some natural
disturbances. Evolution of land usage and measurements of other water
physicochemical parameters (such as heavy metal, pesticides and nutrients)
should be considered, to assess the health of seagrass ecosystem at the study

The ethnotaxa ‘Saethu pasi’ (H. ovalis) is found in dark water zones
that have a muddy substratum. Fishermen find these muddy or ‘saethu’ zones very
interesting because they provide habitat for numerous crabs, shrimps and fish.
Although it is difficult for a trained taxonomist to distinguish H. ovata (‘Pottal pasi’) from H. ovalis (‘Saethu pasi’) without using
macroscopic characters (e.g., seed number and cross venation pattern), local
people can easily distinguish the two species based on the different habitats
they grow in predominant species are Cymodocea
rotundata, Cymodocea serrulata, Halodule pinifolia, Halophila ovalis, Syringodium isoetifolium and Thalassia hemprichii. These seagrasses provide critical habitat for
diverse marine fauna such as cuttlefish, dugongs, sea horses, eels, rays and
scorpion fish, sea cucumbers and sea snakes, among others. He alsoreported the
importance of seagrasses to local coastal economies in the state of Tamil Nadu
is apparent by the engagement of the conmunity in collecting and sorting
seagrasses. In fact, trading depots are established along the coast where
people trade or buy local produce including seagrasses (Newmaster et al., 2011).