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Seaweeds are considered as a source of
bioactive compounds as they are able to
produce a great variety of secondary
metabolites characterized by a broad spectrum
of biological activities including antiviral,
antibacterial, antifimgal and anticancer
properties. The potentials of Sri Lankan
seaweeds for the development of novel
therapeutic agents remain unexploited.
In this context, antibacterial susceptibility
testing (ABST) of methanolic extracts of
Padina antillarum, Caulerpa lentillifera,
Sargassum sp. and Gracilaria corticata were
conducted against two gram-positive
{Staphylococcus aureus-ATCC 2593, Bacillus
sp.) and two gram-negative {Escherichia coliATCC 25922, Pseudomonas aeruginosaATCC 2785) pathogenic bacteria by agar
disc diffusion method. The extracts were
subjected to qualitative phytochemical
analysis.
The crude methanolic extracts of P. antillarum
showed an antibacterial activity against three
out of four bacterial strains namely S. aureus
(21.33±1.53mm), Bacillus sp.
(21.33±0.58mm), P. aeruginosa
(17.33±1.15mm) within 24 hours. The extract
of C. lentillifera was found to be effective only against S. aureus (17.67±0.58inm) within 24
hours. There were no inhibitory effects
detected for any o f the tested bacteria with the
extracts of Sargassum sp. and G. corticata
within 24 hours. The phytochemical analysis
of the extracts revealed the presence of at least
two phytochemicals among Alkaloids,
Terpenoids, Flavonoids, Saponins, Tannins,
Cardiac glycosides and Anthraquinones.
The results of the present study showed the
potential of seaweeds as a source of
antibacterial compounds. Further studies are
needed to carry out for the isolation and
identification of the active compounds which
can be chemical leads for the development of
novel antibacterial agents
