Quercetin is a flavonoid compound widely present in plants and exhibits a variety of biological activities. Research on quercetin has shown its potential for medical application. In this research, we elucidate its antioxidant mechanism and the broad-spectrum antibacterial and antiparasite properties; summarise its potential application in antioncology and cardiovascular protection and anti-immunosuppression treatment; and demonstrate its ability to alleviate the toxicity of mycotoxins. This research is expected to offer some insights and inspirations for the further study of quercetin, its properties, and the scientific basis for its better application in clinical practice.

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Quercetin: Its Main Pharmacological Activity and Potential Application in Clinical Medicine.

The microtiter assay is one of the most widely used methods for assessing biofilm formation. Though it has high throughput, this assay is known for its substantial deviation from experiment to experiment, and even from well to well. Since the assay constitutes one of the pillars of biofilm research, it was decided to examine the wells of a microtiter plate directly during growth, treatment, and the steps involved in crystal violet (CV) measurements. An inverted Zeiss LSM 880 confocal laser scanning microscope was used to visualize and quantify biomass directly in the wells of the microtiter plate. Green fluorescent protein-tagged Pseudomonas aeruginosa, PAO1, and live/dead stains were used to assess the structure, state, and position of biomass build-up. Microscopic observations were compared with colony-forming unit (CFU) and CV measurements. The development and the structured architecture of biomass was observed in real-time in the wells. Three-dimensional images of biomass were obtained from all of the microtiter wells; these showed variations from well to well. CV staining showed large variations in remaining biomass, depending on the method selected to remove the supernatant prior to CV staining (i.e. pipetting or manually discarding the fluid by inversion, washed or unwashed wells). Colony-forming unit counts or live/dead staining used to evaluate biomass with or without antibiotic treatment proved imprecise due to aggregation, limited removal of biomass, and overestimation of dead staining. The highly structured microenvironment of biomass in microtiter wells needs to be considered when designing and analyzing experiments. When using microtiter plates, stochastic variation due to growth and handling may lead to flawed conclusions. It is therefore recommended that this assay be used as a screening tool rather than as a stand-alone experimental tool.

Into the well-A close look at the complex structures of a microtiter biofilm and the crystal violet assay.

In-depth metabolic profiling, also termed metabolomics, provides detailed information about the biochemical phenotype of an organism. Besides improving our understanding of biochemical processes, metabolomics is used for environmental monitoring, natural product discovery, or even chemotaxonomy, among others. However, for marine macroalgae, comparative large-scale metabolomics studies are lacking, even though seaweeds belong to the most important aquatic primary producers. In this study, we present via a broad scale systematic metabolomics survey 391 metabolites from 21 seaweeds species, representing brown, red and green algae. We demonstrate clear differences in metabolite composition of these seaweeds, reflecting their taxonomic classification. We highlight these differences for amino acid, amino acid derivative and peptide metabolites, energy and carbohydrate metabolites, for lipid, fatty acid and sterol metabolites and for secondary metabolites, including selected metabolic pathways such as the urea cycle, the citrate cycle and the glyconeogenesis/glycolysis, besides others. Additionally, we link selected seaweed biochemical properties to potential pharmaceutical and nutraceutical applications.

In-depth metabolic profiling of marine macroalgae confirms strong biochemical differences between brown, red and green algae

Urate is a major antioxidant as well as the enzymatic end product of purine metabolism in humans. Higher levels correlate with a reduced risk of developing Parkinson's disease (PD) and with a slower rate of PD progression. In this study we investigated the effects of modulating intracellular urate concentration on 1-methyl-4-phenyl-pyridinium (MPP+)-induced degeneration of dopaminergic neurons in cultures of mouse ventral mesencephalon prepared to contain low (neuron-enriched cultures) or high (neuron-glial cultures) percentage of astrocytes. Urate, added to the cultures 24 hours before and during treatment with MPP+, attenuated the loss of dopaminergic neurons in neuron-enriched cultures and fully prevented their loss and atrophy in neuron-astrocyte cultures. Exogenous urate was found to increase intracellular urate content in cortical neuronal cultures. To assess the effect of reducing cellular urate content on MPP+-induced toxicity, mesencephalic neurons were prepared from mice over-expressing urate oxidase (UOx). Transgenic UOx expression decreased endogenous urate content both in neurons and astrocytes. Dopaminergic neurons expressing UOx were more susceptible to MPP+ in mesencephalic neuron-enriched cultures and to a greater extent in mesencephalic neuron-astrocyte cultures. Our findings correlate intracellular urate content in dopaminergic neurons with their toxin resistance in a cellular model of PD and suggest a facilitative role for astrocytes in the neuroprotective effect of urate.

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Urate and Its Transgenic Depletion Modulate Neuronal Vulnerability in a Cellular Model of Parkinson's Disease

Quercetin, an essential plant flavonoid, possesses a variety of pharmacological activities. Extensive literature investigates its antimicrobial activity and possible mechanism of action. Quercetin has been shown to inhibit the growth of different Gram-positive and Gram-negative bacteria as well as fungi and viruses. The mechanism of its antimicrobial action includes cell membrane damage, change of membrane permeability, inhibition of synthesis of nucleic acids and proteins, reduction of expression of virulence factors, mitochondrial dysfunction, and preventing biofilm formation. Quercetin has also been shown to inhibit the growth of various drug-resistant microorganisms, thereby suggesting its use as a potent antimicrobial agent against drug-resistant strains. Furthermore, certain structural modifications of quercetin have sometimes been shown to enhance its antimicrobial activity compared to that of the parent molecule. In this review, we have summarized the antimicrobial activity of quercetin with a special focus on its mechanistic principle. Therefore, this review will provide further insights into the scientific understanding of quercetin’s mechanism of action, and the implications for its use as a clinically relevant antimicrobial agent.

https://www.mdpi.com/1420-3049/27/8/2494/pdf?version=1649767293

Antimicrobial Activity of Quercetin: An Approach to Its Mechanistic Principle

Identification of cytidine 2′,3′-cyclic monophosphate and uridine 2′,3′-cyclic monophosphate in Pseudomonas fluorescens pfo-1 culture

Microtiter plate-based bacterial biofilm assay is frequently used to study bacterial biofilm development and growth While this assay is simple and relatively high-throughput, it frequently shows difficulty in establishing robust biofilm attachment in the wells We report that the consistency of bacterial biofilm assays carried out in microtiter plates subjected to abrasive treatment, by sandblasting or drill press grinding, is significantly improved in a Pseudomonas fluorescens Pf0-1 model Scanning electron microscopy imaging suggests that the treated surfaces could provide points of attachment to facilitate the recruitment of bacteria in the initial phase of biofilm colony establishment The sandblast treated polypropylene, but not polystyrene, plates were found suitable in studying the impact of flavonoid quercetin on the biofilm formation in Bacillus subtilis FB17 Further investigation revealed that due to the hydrophobicity of the polystyrene surfaces, a greater amount of quercetin was adsorbed on the plate surface, effectively lowering the concentration of the flavonoid in solution

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Emily Bordeleau

Papers

Identification of cytidine 2′,3′-cyclic monophosphate and uridine 2′,3′-cyclic monophosphate in Pseudomonas fluorescens pfo-1 culture

Abrasive treatment of microtiter plates improves the reproducibility of bacterial biofilm assays