Abstract:
Recently, there has been a great deal of interest in natural substances and bioactive
compounds as alternatives to synthetic products.
Seaweeds particularly red algae produce a wide variety of metabolites (polyphenols,
flavonoids, carotenoids…). Considered to be active compounds with a broad spectrum of
biological activities (antifungal, antibacterial, antioxidant…).
The aim of this study was to assess and determine the antimicrobial activity of
extracts of the red seaweed Asparagopsis armata against pathogenic microbial strains.
The extraction method used is maceration in four solvents: Methanol,
dichloromethane, hexane and acetone. The yield from the methanol extract was the highest.
Phytochemical screening of the two extracts, methanol and dichloromethane, revealed the
presence of several secondary metabolites like phenols, flavonoids, terpenoids and
carotenoids. The antimicrobial activity of these two extracts was tested at different
concentrations.
Antibacterial testing of the studied extracts was carried out using the disc diffusion
method against five bacterial strains: three gram positive (Bacillus subtilis ATCC 6633,
Listeria monocytogenes ATCC 13932 and Staphylococcus aureus 639c) and two gram
negative (Escherichia coli and Pseudomonas aeruginosa). Antibiograms were used as
positive controls.
The dichloromethane extract exhibited the best antibacterial effect with inhibitory
diameters that vary between 9±0 mm and 26±0 mm. The strain L. monocytogenes was the
most sensitive to both extracts at all concentrations. The strains were sensitive to some of the
antibiotics tested.
The method of direct contact was used to evaluate the antifungal activity against four
strains: Aspergillus carbonarius M 333, Aspergillus flavus NRRL 3251, Aspergillus
ochraceus ATCC 3174, Penicillium glabrum. Positive controls were tested with the
antifungal Nystatin.
The results showed antifungal activity, more remarkable in methanolic extract with
inhibitory rates up to 100% for A. carbonarius and P. glabrum. Nystatin completely inhibited
the growth of all fungi.
