Molecular Networking and spectral techniques for isolation and structure identification of compounds from seaweeds

1 Satomy A. Kami, 1 Maria Gabriela A. Barros, 1 Ana Cláudia Philippus, 1 Gabriele A. Zatelli,1 Lucas F.O.Vieira, 1 Louis P. Sandjo, Lorene Armstrong, 1 Miriam Falkenberg

1 Federal University of Santa Catarina, Postgraduation Program in Pharmacy, Florianópolis, Brazil.
E-mail: [email protected]
Chemical and biological studies with Brazilian algae started in the years 1960s, mostly with material from Rio de Janeiro and São Paulo coasts. In the last decade, a number of calls for projects on marine biodiversity stimulated integrated projects such as the ones sponsored by the Brazilian Council of Research (Sisbiota, ProspecMar). This allowed the access to materials from oceanic islands as well from several points of the continental coast, whose have been subjected to innovative approaches involving biodiversity, chemistry, ecology, evolution and biotechnology. The algal materials were collected in Fernando de Noronha, Atol das Rocas, Sao Pedro and Sao Paulo, as well as in Trindade Islands. The dried algae were extracted with dichloromethane/methanol 2:1 at room temperature; after elimination of the solvent, the extracts were evaluated for antimicrobial, anticoagulant and antiaggregant activities. Thirteen bioactive crude extracts of brown (Dictyopteris, Dictyota and Canistrocarpus) collected in different places or seasons were analyzed in a standardized exploratory method at final concentration of each sample at 2.0 mg/mL and eluted at 0.3 mL/min in an aliquot of 1.0 µL in a range of 100−1500 m/z. All chromatograms of MS/MS were digitally converted to mzML files using MSConvert software (www. proteowizard.sourceforge.net) and one blank injection were submitted to GNPS molecular networking (http://gnps.ucsd.edu). The molecular networking was generated interconnecting MS/MS spectra and displayed on Cytoscape 3.5.1. In spite of the scarcity of data for Brazilian species on GNPS, based on MS data from the literature it was possible to target mass values compatible with diterpenes, disulfides, hydroquinones and steroids. Extracts from different species presented some metabolites in common or related; some extracts from the same species collected in different places or depths showed interesting differences that may involve ecological aspects and should be further investigated. For some extracts, it was possible to identify mass values corresponding to metabolites that were not isolated so far from these species. These metabolites are being targeted for isolation, and so far, two diterpenes and a disulfide were already isolated. Dilophic acid was isolated from Canistrocarpus cervicornis, a diacetal diterpene was obtained from Dictyota mertensii and a disulphide was isolated from Dictyopteris jolyana species. All of them were new records for the respective species. The data of compounds isolated in this study are going to be incorporated into the GNPS database aiming to contribute with further analyses.