Antibacterial Activity and Amphidinol Profiling of the Marine Dinoflagellate Amphidinium carterae (Subclade III)

Abstract

Microalgae have received growing interest for their capacity to produce bioactive metabolites. This study aimed at characterising the antimicrobial potential of the marine dinoflagellate Amphidinium carterae strain LACW11, isolated from the west of Ireland. Amphidinolides have been identified as cytotoxic polyoxygenated polyketides produced by several Amphidinium species. Phylogenetic inference assigned our strain to Amphidinium carterae subclade III, along with isolates interspersed in different geographic regions. A two-stage extraction and fractionation process of the biomass was carried out. Extracts obtained after stage-1 were tested for bioactivity against bacterial ATCC strains of Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa. The stage-2 solid phase extraction provided 16 fractions, which were tested against S. aureus and E. faecalis. Fractions I, J and K yielded minimum inhibitory concentrations between 16 μg/mL and 256 μg/mL for both Gram-positive. A targeted metabolomic approach using UHPLC-HRMS/MS analysis applied on fractions G to J evidenced the presence of amphidinol type compounds AM-A, AM-B, AM-22 and a new derivative dehydroAM-A, with characteristic masses of m/z 1361, 1463, 1667 and 1343, respectively. Combining the results of the biological assays with the targeted metabolomic approach, we could conclude that AM-A and the new derivative dehydroAM-A are responsible for the detected antimicrobial bioactivity.

In Vitro Antibacterial Activity of Marine Microalgae Extract against Vibrio harveyi

“…Many bioactive and pharmacologically active chemicals, particularly antibacterial compounds, are potentially produced by marine microalgae [6,20,21]. Furthermore, microalgae are gaining popularity due to their ability to create bioactive metabolites with anticancer, anti-inflammatory, antibacterial, and antioxidant effects [11,22]. Previous studies have suggested that fatty acids [23], terpenoids, carbohydrates [24], peptides, polysaccharides, and alkaloids are responsible for antibacterial activity in microalgae [25].…”

“…Novel antibacterial substances were also discovered in microalgae, with Coccomyxa onubensis fatty acid extracts inhibiting E.coli and P. mirabilis [26]. Furthermore, microalgae have been increasingly treated with other compounds such as cyanovirin, oleic acid, linoleic acid, palmitoleic acid, -carotene, or phycocyanin, which have antioxidant or anti-inflammatory properties, as well as antimicrobial activity, such as against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) [22,23].…”

Marine natural products

“…340 Other compounds were claimed but were only established by MS-methods and their structures are not shown here. [341][342][343] The total synthesis of limaol has been achieved, 344 while the relative and absolute congurations of formosalide A 884 and B 885 have been established following their syntheses. 345 Two groups have independently synthesised and determined the full stereostructure of amphirionin-2 886.…”

“…Other compounds were claimed but were only established by MS-methods and their structures are not shown here. 341–343…”

First Identification of Amphidinols from Mexican Strains and New Analogs

“…In some of these events, Amphidinium bHABs have been related to fish kills, with A. carterae , A. gibossum , A. massartii, and A. operculatum reported as ichthyotoxin producers [ 5 , 6 , 8 , 9 , 10 , 11 ]. However, besides fish toxicity, some polyketides produced by Amphidinium species have been shown to possess potentially useful bioactivities, such as antifungal, cytotoxic, and antimicrobial bioactivities [ 12 , 13 , 14 ]. Yet, only some of the members of the genus or the species, and not even all members of the same strain, can synthesize these polyketides [ 15 ].…”