Toxicity Bioassay and Cytotoxic Effects of the Benthic Marine Dinoflagellate Amphidinium operculatum

Abstract

Benthic dinoflagellates produce a wide array of bioactive compounds, primarily polyketides, that cause toxic effects on human consumers of seafood and perhaps mediate species interactions in the benthic microenvironment. This study assesses toxic and other bioactive effects of the benthic dinoflagellate Amphidinium operculatum (strain AA60) in two targeted bioassays. The brine shrimp (Artemia salina) bioassay revealed lethal effects of direct exposure to live dinoflagellate cells (Treatment A) and even higher potency with ethanolic extracts of lysed cells (Treatment D). There were no inimical bioactive effects of components released to the aqueous growth medium (Treatment B) or from aqueous cell lysates (Treatment C). The hypothesis that released bioactive compounds provide a chemical defense against metazoan grazers is therefore not supported by these results. The cytotoxic effect of ethanolic crude extracts of this dinoflagellate exhibited mild to high growth reduction effects on six human cancer cell lines. In particular, crude cell-free extracts proved highly growth-inhibitory activity towards breast and lung cancer cell lines MCF-7 and SKLU-1, respectively. Preliminary anti-cancer results indicate that natural bioactive compounds from Amphidinium are worthy of structural characterization and further toxicological investigation as potential therapeutants.

A review on marine benthic dinoflagellates in Mexico

“…Amphidiniella sp. Núñez-Vázquez, 2005;Okolodkov et al, 2007Okolodkov et al, , 2014Okolodkov et al, , 2016Gárate-Lizárraga, 2012, 2020Hernández-Castro, 2017;Aguilar-Trujillo et al, 2014Almazán-Becerril et al, 2015;Martínez-Cruz et al, 2015 Okolodkov & Gárate-Lizárraga, 2006;Okolodkov et al, 2007Okolodkov et al, , 2014Morquecho et al, 2016;Almazán-Becerril et al, 2016b Okolodkov et al, 2007Okolodkov et al, , 2014Okolodkov et al, , 2016Aguilar-Trujillo et al, 2014Almazán-Becerril et al, 2015, 2016bIrola-Sansores et al, 2018;Méndez-Torres, 2019 The first sequence data for genus Amphidinium from Mexico was provided from the study to determine the toxigenicity and cytotoxic effects of A. operculatum in culture (Mejía-Camacho et al, 2021). The identification of Amphidinium strain AA60 as A. operculatum was confirmed by SEM and sequencing of the LSU and ITS regions of rDNA.…”

“…comm.). The non-AMproducing Amphidinium isolates (AA39, AA40, and AA60) have shown significant cytotoxic activities against cancer cell lines (Mejía-Camacho, 2020; Mejía-Camacho et al, 2021), meaning that this bioactivity could be expressed by unknown metabolites other than AMs.…”

“…In fact, the first known culture of a benthic dinoflagellate from Mexican coastal waters was a strain of P. lima established from Isla El Pardito, Baja California Sur, after the poisoning of five local fishermen by consumption of fish liver from the area. et al, 2012;Hernández-Becerril et al, 2013;Hoppenrath et al, 2014;Litaker et al, 2017;Cembella et al, 2021;Mejía-Camacho et al, 2021;Durán-Riveroll et al, 2022). Toxin acronym codes: OA = okadaic acid; OA-D8 = okadaic acid diol-ester; DTX1: dinophysistoxin 1; DTX1-D8 = dinophysistoxin 1 diol-ester; DTX1a = undescribed isomer of DTX1; DTX1a-D8: undescribed isomer of DTX1a-D8; UNK = unknown, unpublished, or unconfirmed.…”

Morphological and Molecular Characterization of the Benthic Dinoflagellate Amphidinium from Coastal Waters of Mexico

“…At this stage, it is premature to consider these polyketides as toxins because the specific toxicity of most of them against defined molecular targets remains undefined. Nevertheless, many of these Amphidinium polyketides have exhibited fungal and hemolytic bioactivity [15][16][17] and in some cases cytotoxic effects against certain cancer cell lines [18,19].…”