Antimicrobial Fatty Acids from Green AlgaUlva rigida(Chlorophyta)

Abstract

This study deals with the antimicrobial potential assessment of Ulva rigida, in regard to collection period and sampling site. Besides, we assess the chemical composition of bioactive compounds. For this purpose, Ulva rigida was seasonally collected from two northern sites in Tunisia, Cap Zebib rocky shore (CZ) and Ghar El Melh lagoon (GEM). Crude organic extracts were prepared using dichloromethane and dichloromethane/methanol and tested against 19 indicator microorganisms using the disk diffusion method and microdilution technique to determine the minimum inhibitory concentration (MIC). Silica gel column and thin layer chromatography were used for purification of active compounds. Nuclear magnetic resonance (NMR) and gas chromatography were used for compounds identification. Samples of Ulva rigida collected from the two sites have uniform antimicrobial activity throughout the year. Algae collected from the lagoon showed the largest spectrum of activity and were used for subsequent analysis. Bioguided purification of extracts from Ulva rigida, collected at GEM, leads to 16 active fractions with antibacterial effect mainly against Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212. These fractions were identified as fatty acids, mainly oleic (C18: 1 w9), linoleic (C18: 2 w6), palmitic (C16: 0), and stearic (C14: 0). MICs values ranged from 10 to 250 μg/ml.

Domesticated Populations of Codium tomentosum Display Lipid Extracts with Lower Seasonal Shifts than Conspecifics from the Wild—Relevance for Biotechnological Applications of this Green Seaweed

“…Algae present multiple mechanisms of chemical defense against biotic (e.g., pathogen infections, grazers, and epiphytes) and abiotic (e.g., UV radiation, osmotic stress, and desiccation) stressors [50,51]. Intertidal marine algae experience extreme conditions during the tidal cycle, being exposed to intense light, temperature fluctuations, desiccation, and osmotic stress, which ultimately lead to the formation of oxidizing agents, such as free radicals, that could damage their structural components [52].…”

“…For an evaluation of the radical stability, a volume of 150 µL of ethanol was added to 15 microplate wells followed by addition of 150 µL of ABTS •+ diluted solution and an incubation period of 120 min, with absorbance measured at 734 nm every 5 min. For an evaluation of the radical scavenging potential, a volume of 150 µL of lipid extract (50,100,200, and 500 µg mL −1 in ethanol) and 150 µL of Trolox standard solution (4,8,16,28,40, and 56 µmol L −1 in ethanol) were placed in each well followed by addition of 150 µL of ABTS •+ diluted solution, and a new incubation period of 120 min, with absorbance measurements at 734 nm every 5 min. The control lipid extracts were also assayed by replacing 150 µL of ABTS •+ diluted solution by 150 µL of ethanol.…”

Antibacterial Use of Macroalgae Compounds against Foodborne Pathogens

“…Among Chlorophyta, the genus Ulva spp. was reported in most of the studies against S. aureus [ 45 , 50 , 66 , 80 , 125 , 126 , 127 , 128 ]. Some studies compared solvent extraction performance for extraction of bioactive compounds: for C. socialis (MeOH > acetone) [ 118 ], U. flexuosa (ethylacetate > MeOH) and for U. rigida (ethanol > Hex> CHCl 3 ).…”

“…In addition, some research made using the red algae G. multipartite showcased that there was a connection between the season when the specimen was collected and its antimicrobial effect against E. coli [ 56 ]. This effect was further proven by an antibiogram made using the algae U. rigida [ 80 ]. The main technique used to obtain bioactive compounds from algae is maceration using different solvents, even though chemicals such as chloroform are still used, the majority of studies use methanol, ethanol and water, as shown in Table 1 .…”

Chemically Diverse and Biologically Active Secondary Metabolites from Marine Phylum chlorophyta

“…consists of bromophenols that pointed out inhibitory activity against both Bacillus subtilis and Staphylococcus aureus , which were also active against Pseudomonas aeruginosa as well as Escherichia coli, Serratia marcesens and Candida albicans [ 8 ]. Utricularia rigida composed of fatty acid obtained from Ghar el Melh lagoon can be used for the development of innovative antibacterial ingredients against human marine diseases [ 106 ].…”