The pyrrole-imidazoles, a group of alkaloids commonly found in marine sponges belonging to the genus Agelas, display a wide range of biological activities. Herein, we report the first chemical study of the secondary metabolites of the sponge A. dilatata from the coastal area of the Yucatan Peninsula (Mexico). In this study, we isolated eight known alkaloids from an organic extract of the sponge. We used NMR and MS analysis and comparison with existing databases to characterize the alkaloids: ageliferin (1), bromoageliferin (2), dibromoageliferin (3), sceptrin (4), nakamuric acid (5), 4-bromo-1H-pyrrole-2-carboxylic acid (6), 4,5-dibromopyrrole-2-carboxylic acid (7) and 3,7-dimethylisoguanine (8). We also evaluated, for the first time, the activity of these alkaloids against the most problematic multidrug-resistant (MDR) pathogens, i.e., the Gram-negative bacteria Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii. Bromoageliferin (2) displayed significant activity against P. aeruginosa. Comparison of the antibacterial activity of ageliferins 1–3 (of similar structure) against P. aeruginosa revealed some relationship between structure and activity. Furthermore, in in vitro assays, 2 inhibited growth and biofilm production in clinical strains of P. aeruginosa. Moreover, 2 increased the survival time in an in vivo Galleria mellonella model of infection. The findings confirm bromoageliferin (2) as a potential lead for designing new antibacterial drugs.

Mexico is one of the three areas of the world with the greatest terrestrial and cultural biological diversity. The diversity of Mexican medicinal flora has been studied for a long time and several bioactive compounds have been isolated. The investigation of marine resources, and particularly the potential of Mexican marine resources, has not been intensively investigated, even though the Yucatan Peninsula occupies 17.4% of the total of the Mexican coast, with great biological diversity in its coasts and the ocean. There are very few studies on the chemistry of natural products from marine organisms that were collected along the coasts of the Yucatan Peninsula and most of them are limited to the evaluation of the biological activity of their organic extracts. The investigations carried out on marine species from the Yucatan Peninsula resulted in the identification of a wide structural variety of natural products that include polyketides, terpenoids, nitrogen compounds, and biopolymers with cytotoxic, antibacterial, antifouling, and neurotoxic activities. This review describes the literature of bioprospecting and the exploration of the natural product diversity of marine organisms from the coasts of the Yucatan Peninsula up to mid-2019.

A total of 51 sponges (Porifera) and 13 ascidians (Chordata) were collected on the coast of the Yucatan Peninsula (Mexico) and extracted with organic solvents. The resulting extracts were screened for antibacterial activity against four multidrug-resistant (MDR) bacterial pathogens: the Gram-negative Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa and the Gram-positive Staphylococcus aureus. The minimum inhibitory concentrations (MICs) of the organic extracts of each marine organism were determined using a broth microdilution assay. Extracts of eight of the species, in particular the Agelas citrina and Haliclona (Rhizoniera) curacaoensis, displayed activity against some of the pathogens tested. Some of the extracts showed similar MIC values to known antibiotics such as penicillins and aminoglycosides. This study is the first to carry out antimicrobial screening of extracts of marine sponges and ascidians collected from the Yucatan Peninsula. Bioassay-guided fractionation of the active extracts from the sponges Amphimedon compressa and A. citrina displayed, as a preliminary result, that an inseparable mixture of halitoxins and amphitoxins and (-)-agelasine B, respectively, are the major compounds responsible for their corresponding antibacterial activities. This is the first report of the antimicrobial activity of halitoxins and amphitoxins against major multidrug-resistant human pathogens. The promising antibacterial activities detected in this study indicate the coast of Yucatan Peninsula as a potential source of a great variety of marine organisms worthy of further research.

Viral infections are one of the main human health problems in recent decades and the cancer remains one of the most lethal diseases worldwide. The development of new antiviral drugs for the treatment of human adenovirus (HAdV) infections continues to be a challenging goal for medicinal chemistry. There is no specific antiviral drug approved to treat infections caused by HAdV so far and the off-label treatments currently available show great variability in their effectiveness. In relation to cancer, most of the available drugs are designed to act on specific targets by altering the activity of involved transporters and genes. Taking into account the high antiviral and antiproliferative activity against tumor cell lines displayed by some marine natural products reported in the literature, sixty five marine organisms were selected: 51 sponges (Porifera), 13 ascidians (Chordata), and 1 gorgonian (Cnidaria), collected from Yucatan Peninsula, Mexico, to evaluate their antiviral activity against human adenovirus type 5 (HAdV5) and their anticancer properties against five human tumor cell lines, namely human lung carcinoma (A549), human skin melanoma (A2058), hepatocyte carcinoma (HepG2), breast adenocarcinoma (MCF7), and pancreas carcinoma (MiaPaca-2). Eleven extracts displayed anti-HAdV activity being the organic extracts of Dysidea sp., Agelas citrina, Chondrilla sp., Spongia tubulifera, and Monanchora arbuscula the five most active ones. On the other hand, 24 extracts showed antiproliferative activity against at least one tumor cell line, being the extracts of the ascidian Eudistoma amanitum and the sponge Haliclona (Rhizoniera) curacaoensis the most active ones. This work constitutes the first wide antiviral and antiproliferative screening report of extracts from the marine sponges, ascidians, and a gorgonian collected from the Yucatan Peninsula, Mexico.