Metabolite profiling of the benthic diatom Cocconeis scutellum by GC-MS

Cocconeis scutellum is a benthic diatom producing one or more compounds responsible for the early programmed cell death (apoptosis) of the male gonad and the androgenic gland of the protandric shrimp Hippolyte inermis Leach. The metabolite composition of both the ether and butanol extracts was studied by gas chromatography-mass spectrometry (GC-MS) in both electron impact (EI) and chemical ionization (CI) mode. The compounds were identified as trimethylsilyl (TMSi) derivatives. The structure of the fatty acids (FA) was confirmed after conversion to their methyl esters. The ether fraction of C. scutellum contained FA (76%), of which 30% were saturated (SFA), 24% monounsaturated (MUFA) and 22% polyunsaturated (PUFA). Mono- (8%) and diglycerides (3%) as well as sterols (5%) and isoprenoid compounds (4%) were also found in this fraction. The butanol extract consisted of FA (45%), carbohydrates (25%), amino acids and N-containing metabolites (10%), fatty alcohols (9%), glycerides (4%) and organic acids (3%). In the literature, many reports deal with the chemistry and the chemical ecology of planktonic diatoms; contrastingly, benthic species are still less studied, especially with respect to their chemical composition, due to their difficult cultivation. Hence, our investigation represents a preliminary approach to clarify on chemical bases the ecological role of Cocconeis on decapods in the marine benthos, as well as a description of the metabolic pattern of this benthic diatom.