Synthesis and hLDH Inhibitory Activity of Analogues to Natural Products with 2,8-Dioxabicyclo[3.3.1]nonane Scaffold

Evaluation of Antibacterial and Antibiofilm Properties of Phenolics with Coumarin, Naphthoquinone and Pyranone Moieties Against Foodborne Microorganisms

Numerous studies have previously demonstrated the antimicrobial activity of plant extracts rich in procyanidins. However, these investigations that focused on uncharacterized extracts do not provide information on the structure-activity relationships of these compounds. The aim of this work was to investigate the antibacterial and antibiofilm properties of 27 phenolics with coumarin, naphthoquinone and pyranone moieties against foodborne microorganisms, as well as to establish structure-activity relationships. Minimal inhibitory concentrations (MICs) for each compound were investigated, as well as their ability for inhibiting biofilm formation as well as disrupting previously formed biofilms by food pathogens. Our compounds show high antibacterial and antibiofilm activities against Gram-positive bacteria. Regarding the structure-activity relationships observed, the coumarin moiety seems to favor the antibacterial activity against both S. aureus strains assayed, while a naphthoquinone moiety enhances antibacterial effects against B. cereus. Moreover, the replacement of OH groups in the B-ring by methoxy groups impairs antibacterial activity of the compounds against target bacteria, while the presence of Cl or OH groups in the molecules seems to enhance the inhibition of biofilm formation as well as the disruption of preformed biofilms. These results may be of great relevance for the food sector, increasing the options of additives that can be used industrially.

Synthesis and hLDHA Inhibitory Activity of New Stiripentol-Related Compounds of Potential Use in Primary Hyperoxaluria

Human lactate dehydrogenase A (hLDHA) is a homotetrameric isozyme involved in the conversion of glyoxylate into oxalate in the cytosol of liver cells (hepatocytes) and partially responsible for the overproduction of oxalate in patients with the rare disease called primary hyperoxaluria (PH). Recently, hLDHA inhibition has been validated as a safe therapeutic method to try to control the PH disease. Stiripentol (STP) is an approved drug used in the treatment of seizures associated with Dravet's syndrome (a severe form of epilepsy in infancy) which, in addition, has been drawing interest in recent years also for potentially treating PH, due to its hLDHA inhibitory activity. In this work, several new STP-related compounds have been synthesized and their hLDHA inhibitory activity has been compared to that of STP. The synthesis of these analogues to STP was accomplished using crossed-aldol condensation guided by lithium enolate chemistry and a successive regioselective reduction of the resulting α,β-unsaturated ketones. The target molecules were obtained as racemates, which were separated into their enantiomers by chiral HPLC. The absolute configurations of pure enantiomers were determined by the modified Mosher's method and electronic circular dichroism (ECD) spectroscopy. For the inhibitory effect over the hLDHA catalytic activity, a kinetic spectrofluorometric assay was used. All the new synthesized compounds turned out to be more active at 500 μM (46-72% of inhibition percentage) than STP (10%), which opens a new line of study on the possible capacity of these analogues to reduce urinary oxalate levels in vivo more efficiently.

Tracking Selective Internalization and Intracellular Dynamics of Modified Chitosan Polymeric Micelles of Interest in Primary Hyperoxaluria Diseases

Primary hyperoxalurias (PHs) represent rare diseases associated with disruptions in glyoxylate metabolism within hepatocytes. Impaired glyoxylate detoxification in PH patients results in its accumulation and subsequent conversion into oxalate, a process catalyzed by the hepatic lactate dehydrogenase A enzyme (hLDHA). Targeting this enzyme selectively in the liver using small organic molecules emerges as a potential therapeutic strategy for PH. However, achieving selective hepatic inhibition of hLDHA poses challenges, requiring precise delivery of potential inhibitors into hepatocytes to mitigate adverse effects in other tissues. Our recent efforts focused on the design of polymeric micelle nanocarriers tailored for the selective transport and release of hLDHA inhibitors into liver tissues. In this study, we synthesized and assessed the internalization and disaggregation dynamics of chitosan-based polymeric micelles in both hepatic and nonhepatic cell models using live-cell imaging. Our findings indicate that lactonolactone residues confer internalization capacity to the micelles upon exposure to cells. Moreover, we demonstrated the intracellular disaggregation capacity of these nanocarriers facilitated by the cystamine redox-sensitive linker attached to the polymer. Importantly, no cytotoxic effects were observed throughout the experimental time frame. Finally, our results underscore the higher selectivity of these nanocarriers for hepatic HepG2 cells compared to other nonhepatic cell models.

Synthesis of Ethyl Pyrimidine-Quinolincarboxylates Selected from Virtual Screening as Enhanced Lactate Dehydrogenase (LDH) Inhibitors

The inhibition of the hLDHA (human lactate dehydrogenase A) enzyme has been demonstrated to be of great importance in the treatment of cancer and other diseases, such as primary hyperoxalurias. In that regard, we have designed, using virtual docking screening, a novel family of ethyl pyrimidine-quinolinecarboxylate derivatives (13-18)(a-d) as enhanced hLDHA inhibitors. These inhibitors were synthesised through a convergent pathway by coupling the key ethyl 2-aminophenylquinoline-4-carboxylate scaffolds (7-12), which were prepared by Pfitzinger synthesis followed by a further esterification, to the different 4-aryl-2-chloropyrimidines (VIII(a-d)) under microwave irradiation at 150-170 °C in a green solvent. The values obtained from the hLDHA inhibition were in line with the preliminary of the preliminary docking results, the most potent ones being those with U-shaped disposition. Thirteen of them showed IC50 values lower than 5 μM, and for four of them (16a, 18b, 18c and 18d), IC50 ≈ 1 μM. Additionally, all compounds with IC50 < 10 μM were also tested against the hLDHB isoenzyme, resulting in three of them (15c, 15d and 16d) being selective to the A isoform, with their hLDHB IC50 > 100 μM, and the other thirteen behaving as double inhibitors.

Halogenated Analogs to Natural A-Type Proanthocyanidins: Evaluation of Their Antioxidant and Antimicrobial Properties and Possible Application in Food Industries

A description of new antimicrobial agents suitable for food industries has become necessary, and natural compounds are being considered as promising sources of new active derivatives to be used with the aim of improving food safety. We have previously described desirable antimicrobial and antibiofilm activities against foodborne bacteria by analogs to A-type proanthocyanidins (PACs) with a nitro (NO2) group at carbon 6 of the A-ring. We report herein the synthesis of eight additional analogs with chloro and bromo atoms at the A-ring and the systematic study of their antimicrobial and antioxidant activities in order to evaluate their possible application as biocides or food preservatives, as well as to elucidate new structure-activity relationships. The results from this study show that halogenated analogs to natural A-type proanthocyanidins rise above the nitro derivatives previously reported in their antimicrobial activities. Gram-positive bacteria are the most sensitive to all the analogs and combinations assayed, showing MICs from 10 to 50 μg/mL in most cases, as well as reductions in biofilm formation and the disruption of preformed biofilms of at least 75%. Some structure-activity relationships previously described have also been corroborated. Analogs with just one OH group at the B-ring show better antimicrobial activities than those with two OH groups, and those analogs with two or three OH groups in the whole structure are more active than those with four OH groups. In addition, the analogs with two OH groups at the B-ring and chloro at the A-ring are the most effective when antibiofilm activities are studied, especially at low concentrations.

Special Issue "Development and Synthesis of Biologically Active Compounds"

The intention of this Special Issue is to focus on new achievements in the design, preparation, and in vitro and in vivo biological evaluation of bioactive molecules that can result in the development of natural or artificial potent compounds looking for promising pharmaceuticals and agrochemicals [...].