Synthesis of coruscanones A and B, metabolites of Piper coruscans, and related compounds

Chemical and Enantioselective Analysis of the Leaf Essential Oil from Piper coruscans Kunth (Piperaceae), a Costal and Amazonian Native Species of Ecuador

In the present study, an essential oil was distilled from the leaves of Piper coruscans Kunth, a native Amazonian species belonging to the family Piperaceae and quite common in Ecuador. The chemical analysis was performed by GC-MS (qualitative) and GC-FID (quantitative), on polar and non-polar columns, detecting a total of 58 compounds of which 52 were identified. All the identified compounds were quantified. The essential oil was mainly constituted of sesquiterpenes (54.1-55.0%) and oxygenated sesquiterpenoids (32.5-33.6%), the major constituents being: (E)-β-caryophyllene (24.1-25.0%), α-humulene (11.6-12.0%), caryophyllene oxide (9.3-10.9%), linalool (4.5-5.2%), humulene epoxide II (3.6-4.1%), (E)-nerolidol (3.7-4.0%), α-copaene (3.7-3.9%), α-muurolol (3.4-3.7%), α-selinene (3.4-3.5%), β-selinene (3.1-3.3%), and one undetermined oxygenated sesquiterpenoid (3.1-3.3%). The aqueous phase (hydrolate) of the distillation process was also submitted to chemical analysis, showing linalool as the main organic compound in solution, with a concentration of 12.3-15.7 mg/100 mL. The essential oil was than analyzed for the enantiomeric distribution of its monoterpene constituents, affording the following enantiomeric excesses in two β-cyclodextrin-based enantioselective columns: (1S,5S)-(-)-α-pinene (60.0-69.6%), (1S,5S)-(-)-β-pinene (5.2-7.2%), (R)-(-)-α-phellandrene (72.5-78.2%), (R)-(+)-limonene (28.6%) and (R)-(-)-linalool (1.8-3.1%).

Bioactivity and Mode of Action of Bacterial Tetramic Acids

Microbially produced 3-acyltetramic acids display a diverse range of biological activities. The pyreudiones are new members of this class that were isolated from bacteria of the genus Pseudomonas. Here, we performed a structure-activity relationship study and determined their mode of action. An efficient biomimetic synthesis was developed to synthesize pyreudione A. Pyreudiones and synthetic analogs thereof were tested for their amoebicidal, antibacterial, antiproliferative, and cytotoxic activities. The length of the alkyl side chain and the nature of the amino acid residues within the tetramic acid moiety strongly affected activity, in particular against mycobacteria. The mode of action was shown to correlate with the ability of pyreudiones to act as protonophores. Removal of the acidic proton by methylation of pyreudione A resulted in a loss of bioactivity.

A comprehensive LC/MS analysis of novel cyclopentenedione library

Cyclopentenediones (CPDs) are compounds with a variety of applications ranging from the preparation of functional polymers to the development of antimicrobial agents, suggesting the potential use of CPDs as novel bioactive compounds or drugs. For this reason, a detailed characterization of CPDs and the development of robust analytical methods for their trace analysis are being sought. Here we focused on the design and synthesis of a library of novelized benzylidene CPD derivatives that were consequently characterized by ultra-high performance liquid chromatography (UHPLC) on-line connected with tandem mass spectrometry (MS/MS). The library design was based on a 2-benzylidene-4-cyclopentene-1,3-dione skeleton substituted with a variety of hydroxy, methoxy, halogen, linear aliphatic, heterocyclic and saccharide moieties, primarily modulating the skeleton's hydrophobicity. The prepared CPDs were effectively ionized by positive/negative atmospheric pressure photoionization (APPI) and atmospheric pressure chemical ionization (APCI). After careful optimization of the dopant composition and flow rate, positive-mode APPI proved to be more sensitive than APCI. In negative mode, both ionization techniques gave similar results. Further, a detailed MS fragmentation study was performed, confirming the structure of the compounds and enabling positional isomers of CPDs to be differentiated on the basis of their collision spectra analysis. Finally, an optimization of the composition of the mobile phase and reversed-phased separation mode were done, followed by a selection of the most suitable UHPLC stationary phases, i.e. C18, C8 and phenyl. The applicability of the method was evaluated by the inclusion of the other two substances in the study, i.e. monomeric and dimeric bioactive CPDs, compound TX-1123 and nostotrebin 6 with cytostatic and antimicrobial activities, respectively. The results presented here could be used in further investigations of the chromatographic retention and MS behavior of CPDs, which could be utilized for their isolation, detailed characterization and analysis in biological systems.