Antimicrobial activity of the newly recorded red alga Grateloupia doryphora collected from the Eastern Harbor, Alexandria, Egypt.

AIMS: To screen the newly recorded alga Grateloupia doryphora in the Egyptian Mediterranean Sea for antimicrobial activity. METHODS AND RESULTS: Algal samples were collected from the Eastern Harbor, Alexandria, Egypt during summer (2016 and 2017). The dry and fresh methanolic, ethanolic and ethyl acetate algal extracts were tested against Bacillus subtilis, Enterococcus faecalis and Staphylococcus aureus as Gram-positive bacteria, Escherichia coli, Pseudomonas aeruginosa as Gram-negative bacteria and one yeast strain Candida albicans. A three-way analysis of variance showed significant differences based on the algal form, type of solvents and microbial species. The fresh methanolic and ethyl acetate extracts had equal effects on the tested pathogens with means of 14·44 and 15·16 respectively. However, the fresh algal extract was more effective on all the tested organisms than the dried material, except for ethyl acetate and ethanol extract on Bacillus subtilis (31 and 23 mm) respectively. In fact, P. aeruginosa was the most susceptible organism to the fresh algal extract, with much higher inhibition zones (30, 27 and 28 mm) for mehanolic, ethyl acetate and ethanolic extracts, respectively, compared with the dried ones. Furthermore, C. albicans was sensitive to the fresh algal extracts only. Compared with the commercial antibiotics piperacillin, rifampicin, cephalexin, metronidazole and fusidic acid tested against the same microbes, the results showed in general lower or comparable inhibition zones than algal extracts. The GC-MS fresh methanolic and ethyl acetate algal extracts revealed the presence of many potent compounds, with palmitic acid and 2-tetradecyloxirane as the common constituents in both extracts. The commercial palmitic acid was tested against the same microbes with successful elimination of all pathogens. CONCLUSIONS: Grateloupia doryphora showed broad spectrum of antimicrobial activity against the tested microbial species in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: The alga can be useful in industry of pharmaceutical products. On the other hand, its usage in this domain can be a suitable solution to its introduction in our coasts.

Seaweeds as bioindicators of heavy metals off a hot spot area on the Egyptian Mediterranean Coast during 2008-2010.

Concentrations of Cu, Zn, Cd, Pb, Ni, Co, Fe, Mn, and Hg were measured successively in water, sediments, and six macroalgal species belonging to three algal classes during 3 years (2008-2010) from Abu Qir Bay, Alexandria, Egypt: Chlorophyceae (Enteromorpha compressa, Ulva fasciata), Phaeophyceae (Padina boryana), and Rhodophyceae (Jania rubens, Hypnea musciformis, Pterocladia capillacea). The study aimed to assess the bioaccumulation potential of the seaweeds, as well as to evaluate the extent of heavy metal contamination in the selected study site. Metals were analyzed using atomic absorption spectrophotometry coupled with MH-10 hydride system. The obtained data showed that the highest mean concentrations of Cu, Zn, Fe, and Mn were recorded in E. compressa; Cd, Ni, and Hg exhibited their highest mean concentrations in P. boryana, while Pb and Co were found in J. rubens. Abundance of the heavy metals in the algal species was as follow: Fe > Mn > Zn > Pb > Ni > Co > Cu > Cd > Hg. E. compressa showed the maximum metal pollution index (MPI) which was 11.55. Bioconcentration factor (BCF) for the metals in algae was relatively high with a maximum value for Mn. The Tomlinson pollution load index (PLI) values for the recorded algal species were low, which ranged between 1.00 in P. boryana and 2.72 in E. compressa. Enrichment factors for sediments were low fluctuating between 0.43 for Hg to 2.33 for Mn. Accordingly, the green alga E. compressa, brown alga P. boryana, and red alga J. rubens can be nominated as bioindicators. Based on MPI and PLI indices, Abu Qir Bay in the present study is considered as low-contaminated area.