The marine environment is a rich source of bioactive compounds with a wide range of applications. In this study, 65 extracts from sponges, ascidians, and a gorgonian collected from the Yucatán Peninsula, Mexico, were evaluated for their modulatory effects on the growth of four microalgal species. Some extracts were found to exhibit pronounced algicidal activity, while others promoted growth. Bioassay-guided fractionation of the extract from Haliclona (Rhizoniera) curacaoensis led to the identification of arenosclerins A and C as potent algicidal agents, active across all tested microalgae. In contrast, the extract from Halichondria melanadocia enhanced microalgal growth, and chemical analysis revealed the presence of medelamine A and B as putative growth-promoting compounds. This study provides a new report on microalgae-modulating activities of marine sponge metabolites. The dual activity observed, both inhibitory and stimulatory, not only contributes to our understanding of marine compound diversity but also underscores the potential of these marine-derived compounds for sustainable environmental management practices.

This study examined the bioactivity profiles and secondary metabolite diversity of 64 crude extracts derived from benthic marine organisms, including 51 extracts from 34 sponge species and 13 extracts from 10 ascidian species, collected across six locations in two regions: the Gulf of Mexico (Alacranes Reef and Progreso) and the Mexican Caribbean (Cozumel, Bermejo, Mahahual, and Rio Indio) on the Yucatán Peninsula. The evaluation focused on five biological activities: cytotoxic, antialgal, antiviral, antifungal, and antibacterial. Results showed that 64.1% of the extracts displayed at least one activity, with 43.7% being cytotoxic, 35.9% antialgal, 25% antiviral, 15.6% antibacterial, and 14.1% antifungal. Using the Spearman correlation method, antifungal and antibacterial activities showed significant correlations in two sponge families, Agelasidae and Aplysinidae (ρ ranging from 0.99 to 0.97, p = 0.01–0.001). The Cozumel and Río Indio localities exhibited the highest number of bioactive extracts; notably, extracts of 15 species demonstrated specific biological activities. Furthermore, a dereplication strategy using ¹³C NMR spectroscopy was applied, aiding in the probable identification of secondary metabolites and clarifying the biological activities of recurrent species from different locations.

The Saudi Arabian Red Sea has been a focus of ongoing scientific exploration due to its extensive, largely untapped marine biodiversity, particularly marine sponges. Marine sponges have long been recognised as a valuable source of unique compounds. In this study, we isolated a new brominated compound (1) from the marine sponge Aiolochroia crassa, collected from the Saudi Arabian Sea, using chromatographic analyses. Molecular networking analysis revealed the presence of brominated molecules in the extract. The identified compound belongs to a class of phosphatidylcholine derivatives. The structure of compound 1 was elucidated using 1D and 2D NMR spectroscopy and high-resolution ESI-Q-TOF mass spectrometry. Further structure confirmation studies were performed using MS/MS fragmentation analysis and DFT calculations for the ¹H and ¹³C NMR chemical shifts. This is the first report of 1 from this species of marine sponges.