Assessment of cytotoxicity in ten strains of Gambierdiscus australes from Macaronesian Islands by neuro-2a cell-based assays

Within the dinoflagellate genus Gambierdiscus several species are well-known producers of ciguatoxins (CTXs) and maitotoxins (MTXs). These compounds are potent marine toxins that accumulate through the food chain, leading to a foodborne disease known as ciguatera when contaminated fish is consumed. Given the threat that the presence of these toxins in seafood may pose to human health and fisheries, there is an evident necessity to assess the potential toxicity of Gambierdiscus sp. in a particular area. Thus, the purpose of this work was to evaluate the production of CTX and MTX of 10 strains of Gambierdiscus australes isolated from the Selvagem Grande Island (Madeira, Portugal) and El Hierro Island (Canary Islands, Spain). The strains were first characterized by light microscopy and species were confirmed by molecular biology, being identified as G. australes. Following the species identification, CTX and MTX production of G. australes extracts was evaluated at the exponential growth phase using neuro-2a cell-based assays. Additionally, the production of MTX was also investigated in two of the G. australes strains collected at the stationary growth phase. Interestingly, 9 out of 10 strains were found to produce CTX-like compounds, ranging from 200 to 697 fg equiv. CTX1B cell(-1). None of the G. australes strains showed MTX-like activity at the exponential phase, but MTX production was observed in two strains at the stationary growth phase (227 and 275 pg equiv. MTX cell(-1)). Therefore, the presence of G. australes strains potentially producing CTX and MTX in these Macaronesian Islands was confirmed.