RESUMEN
Increases in the prevalence of multiply resistant microbes have necessitated the search for new molecules with antimicrobial properties. One noteworthy avenue in this search is inspired by the presence of native antimicrobial peptides in the skin of amphibians. Having the second highest diversity of frogs worldwide, Colombian anurans represent an extensive natural reservoir that could be tapped in this search. Among this diversity, species such as Boana pugnax (the Chirique-Flusse Treefrog) are particularly notable, in that they thrive in a diversity of marginal habitats, utilize both aquatic and arboreal habitats, and are members of one of few genera that are known to mount a robust immunological response against the fungus Batrachochytrium dendrobatidis, which has decimated the population of frogs worldwide. To search for molecules with potential antimicrobial activity, we have assembled and annotated a reference transcriptome from the skin of four wild captured B. pugnax from Antioquia, Colombia. Analysis of potential antimicrobial and immunological components was performed using ontology analyses, we identified several antimicrobial chemokines with particularly strong potential for exhibiting broadscale antimicrobial activities, as well as several genes related to rapid alteration of transcriptional (KRAB zinc finger protein) and phosphorylation (MAPK) responses to exogenous stressors. We also found eight families of transmembrane transport proteins, including sodium, potassium and voltage-dependent calcium channels, which will be invaluable in future studies aimed at more precisely defining the diversity and function of cationic antimicrobial peptides with alpha-helical structures. These data highlight the utility of frogs such as Boana pugnax in the search of new antimicrobial molecules. Moreover, the molecular datasets presented here allow us to expand our knowledge of this species and illustrate the importance of preserving the vast potential of Colombian biodiversity for the identification of useful biomolecules.
RESUMEN
Novel lanthanide (Ln) compounds [Ln(L)2]Cl.xH2O (Ln = La3+, Ce3+, Sm3+) containing aromatic N,O-chelate ligands [HL1 = 4-amino-2-(1H-benzimidazol-2-yl)phenol; HL2 = 5-amino-2-(1H-benzimidazol-2-yl)phenol] have been synthesized and structurally characterized by elemental analysis, NMR and IR spectroscopy, molar conductance measurements, and mass spectrometry (MS). The spectroscopic data suggested that the benzimidazolyl-phenol ligands act as N,O-chelate ligands through the iminic nitrogen and phenolic oxygen atoms. Elemental analysis indicated that lanthanide compounds were formed in a 1:2 stoichiometry (metal:ligand). In vitro biological evaluation was carried out using these complexes, exhibiting moderate cytotoxicity against six different human tumor cell lines (U251, human glioblastoma; HCT-15, colorectal carcinoma; MCF-7, breast epithelial adenocarcinoma; PC-3, prostate cancer; K562, myelogenous leukemia; SKLU-1, lung carcinoma) and lower toxicity against a non-cancerous cell line (COS-7, primate kidney). In addition, the antibacterial activity of the compounds was assessed against two gram-positive strains (Staphylococcus aureus ATCC 25923, Listeria monocytogenes ATCC 19115) and two gram-negative strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27583) using the microdilution method. The results obtained show that the metal complexes exhibit higher biological activity than the free ligands, confirming a synergistic effect. Further benzimidazolyl-phenol derivatives were explored for the detection of bacteria using fluorescence imaging studies. Interestingly, the fluorescent properties of these compounds make them potential candidates to monitor the morphology of bacteria at different compound concentrations. Hence, the interaction of the ligand and complexes with model membranes mimicking those of bacteria was studied by using differential scanning calorimetry (DSC) and molecular dynamics (MD), showing that both compounds decreased the enthalpy of transition in two model membranes as the concentration of the compounds increased. In addition, the main transition temperature was slightly reduced as a result of these interactions.
