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Three new cembranoid diterpenes, knightol (1), knightol acetate (2), and knightal (3), along with the known asperdiol (4) and asperdiol acetate (5), were isolated as major compounds from the sea whip Eunicea knighti collected from the Colombian Caribbean. The structures and absolute configurations of 1-5 were determined on the basis of spectroscopic analyses and by a combination of chemical and NMR methods, multiple correlations observed in a ROESY experiment, and using the modified Mosher method. Additionally, five semisynthetic compounds, 6-10, obtained during the chemical transformations of the natural compounds are here reported for the first time. All compounds were tested for antimicrobial activity against marine bacteria associated with heavily fouled surfaces and were also screened for antiquorum sensing (QS) activity. Compounds 1, 3, and 8 showed significant antimicrobial activity against bacterial isolates, and 1, 3, 7, and 8 showed excellent anti-QS inhibition activity measured by means of bioluminescence inhibition with biosensor model systems.

Three new cembranoid diterpenes, knightine (1), 11(R)-hydroxy-12(20)-en-knightal (2), and 11(R)-hydroxy-12(20)-en-knightol acetate (3), were isolated as minor constituents of the Caribbean gorgonian Eunicea knighti, along with the known cembranoids 4-8. The stereostructures of the new compounds were determined by detailed spectroscopic analyses and a combination of chemical transformations and modified Mosher's methods. All isolated cembranoids were tested against fouling using a quorum-sensing inhibition (QSI) assay and a biofilm inhibition test. Compounds 2, 3, and 6 disrupted QS systems at lower concentrations than kojic acid and Cu(2)O, and in most cases cembranoids 1-8 showed bacterial biofilm inhibition at lower concentrations than kojic acid.

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Marine organisms have evolved to survive against predators in complex marine ecosystems via the production of chemical compounds. Soft corals (cnidaria, Anthozoa, octocorallia) are an important source of chemically diverse metabolites with a broad spectrum of biological activities. Herein, we perform a comparative study between high-resolution proton nuclear magnetic resonance (1 H-nMR) and pure shift yielded by chirp excitation (PSYCHE) experiments to analyze the metabolic profile of 24 soft corals from the Colombian Caribbean to correlate chemical fingerprints with their cytotoxic activity against three cancer cell lines (human cervical carcinoma (SiHa), human prostatic carcinoma (PC3) and human lung adenocarcinoma (A549)). All data obtained were explored using multivariate analysis using principal components analysis (pcA) and orthogonal partial least squares (opLS) analysis. the results did not show a significant correlation between clusters using 1 H-nMR data in the pcA and opLS-DA models and therefore did not provide conclusive evidence; on the other hand, a metabolomic analysis of pSYcHe data obtained under the same parameters revealed that when a decoupled experiment is performed, it was possible to establish a statistically valid correlation between the chemical composition of soft corals and their cytotoxic activity against the PC3 cancer cell line, where the asperdiol and plexaurolone markers were putatively identified and related to the cytotoxic activity presented by extracts of Plexaurella sp. and Plexaura kukenthali, respectively. these results increase the speed, effectiveness and reliability of analyses for the study of this type of complex matrices. Metabolomics studies allow a complete analysis of a set of metabolites that are the substrates and products of metabolism driving essential cellular functions in a given biological system 1. This research has applications in different fields, such as pharmacology, environmental sciences, chemotaxonomy, nutrition and medicine 2. Recently, metabolomic approaches have allowed the understanding of complex biological systems and the biochemical composition of organisms that live in diverse environments, such as marine areas 3. Goulitquer et al. demonstrated that metabolites are important links between genotype and phenotype and are important for studying several biological processes and for analyzing interactions between organisms within communities via mass spectrometry (MS)-based metabolomics 4. In addition, Mohamed A. Farag et al. compared metabolomics results obtained with liquid chromatography coupled to mass spectrometry (LC-MS) with those obtained by nuclear magnetic resonance (NMR) to investigate the metabolism of 16 Sarcophyton species in the context of their genetic diversity and growth habitats 3. The importance of studying marine invertebrates lies in their extraordinary ability to produce a broad variety of chemical compounds with unique chemical structures that in most cases have been correlated with significant biological activities, which ...