Circulating low-molecular-weight (poly)phenol metabolites in the brain: unveiling in vitro and in vivo blood-brain barrier transport.

Circulating metabolites resulting from colonic metabolism of dietary (poly)phenols are highly abundant in the bloodstream, though still marginally explored, particularly concerning their brain accessibility. Our goal is to disclose (poly)phenol metabolites' blood-brain barrier (BBB) transport, in vivo and in vitro, as well as their role at BBB level. For three selected metabolites, benzene-1,2-diol-3-sulfate/benzene-1,3-diol-2-sulfate (pyrogallol-sulfate - Pyr-sulf), benzene-1,3-diol-6-sulfate (phloroglucinol-sulfate - Phlo-sulf), and phenol-3-sulfate (resorcinol-sulfate - Res-sulf), BBB transport was assessed in human brain microvascular endothelial cells (HBMEC). Their potential in modulating in vitro BBB properties at circulating concentrations was also studied. Metabolites' fate towards the brain, liver, kidney, urine, and blood was disclosed in Wistar rats upon injection. Transport kinetics in HBMEC highlighted different BBB permeability rates, where Pyr-sulf emerged as the most in vitro BBB permeable metabolite. Pyr-sulf was also the most potent regarding BBB properties improvement, namely increased beta(ß)-catenin membrane expression and reduction of zonula occludens-1 membrane gaps. Whereas no differences were observed for transferrin, increased expression of caveolin-1 upon Pyr-sulf and Res-sulf treatments was found. Pyr-sulf was also capable of modulating gene and protein expression of some solute carrier transporters. Notably, each of the injected metabolites exhibited a unique tissue distribution in vivo, with the remarkable ability to almost immediately reach the brain.

Environmentally Friendly Degradation and Detoxification of Rifampicin by a Bacterial Laccase and Hydrogen Peroxide.

Antibiotics are micropollutants accumulating in our rivers and wastewaters, potentially leading to bacterial antibiotic resistance, a worldwide problem to which there is no current solution. Here, we have developed an environmentally friendly two-step process to transform the antibiotic rifampicin (RIF) into non-antimicrobial compounds. The process involves an enzymatic oxidation step by the bacterial CotA-laccase and a hydrogen peroxide bleaching step. NMR identified rifampicin quinone as the main product of the enzymatic oxidation. Growth of Escherichia coli strains in the presence of final degradation products (FP) and minimum inhibitory concentration (MIC) measurements confirmed that FP are non-anti-microbial compounds, and bioassays suggest that FP is not toxic to eukaryotic organisms. Moreover, competitive fitness assays between susceptible and RIF-resistant bacteria show that susceptible bacteria is strongly favoured in the presence of FP. Our results show that we have developed a robust and environmentally friendly process to effectively remediate rifampicin from antibiotic contaminated environments.

Mechanistic insights into glycoside 3-oxidases involved in C-glycoside metabolism in soil microorganisms.

C-glycosides are natural products with important biological activities but are recalcitrant to degradation. Glycoside 3-oxidases (G3Oxs) are recently identified bacterial flavo-oxidases from the glucose-methanol-coline (GMC) superfamily that catalyze the oxidation of C-glycosides with the concomitant reduction of O2 to H2O2. This oxidation is followed by C-C acid/base-assisted bond cleavage in two-step C-deglycosylation pathways. Soil and gut microorganisms have different oxidative enzymes, but the details of their catalytic mechanisms are largely unknown. Here, we report that PsG3Ox oxidizes at 50,000-fold higher specificity (kcat/Km) the glucose moiety of mangiferin to 3-keto-mangiferin than free D-glucose to 2-keto-glucose. Analysis of PsG3Ox X-ray crystal structures and PsG3Ox in complex with glucose and mangiferin, combined with mutagenesis and molecular dynamics simulations, reveal distinctive features in the topology surrounding the active site that favor catalytically competent conformational states suitable for recognition, stabilization, and oxidation of the glucose moiety of mangiferin. Furthermore, their distinction to pyranose 2-oxidases (P2Oxs) involved in wood decay and recycling is discussed from an evolutionary, structural, and functional viewpoint.

Self-recycling and partially conservative replication of mycobacterial methylmannose polysaccharides.

The steep increase in nontuberculous mycobacteria (NTM) infections makes understanding their unique physiology an urgent health priority. NTM synthesize two polysaccharides proposed to modulate fatty acid metabolism: the ubiquitous 6-O-methylglucose lipopolysaccharide, and the 3-O-methylmannose polysaccharide (MMP) so far detected in rapidly growing mycobacteria. The recent identification of a unique MMP methyltransferase implicated the adjacent genes in MMP biosynthesis. We report a wide distribution of this gene cluster in NTM, including slowly growing mycobacteria such as Mycobacterium avium, which we reveal to produce MMP. Using a combination of MMP purification and chemoenzymatic syntheses of intermediates, we identified the biosynthetic mechanism of MMP, relying on two enzymes that we characterized biochemically and structurally: a previously undescribed α-endomannosidase that hydrolyses MMP into defined-sized mannoligosaccharides that prime the elongation of new daughter MMP chains by a rare α-(1→4)-mannosyltransferase. Therefore, MMP biogenesis occurs through a partially conservative replication mechanism, whose disruption affected mycobacterial growth rate at low temperature.

Phenolic Compounds from Virgin Olive Oil: Approaches for Their Synthesis and Analogues.

Virgin olive oil (VOO) is the main fat consumed by populations in the Mediterranean basin, and phenolic compounds, minor components of this fat, are known to be responsible for diverse health benefits when consumed in a regular diet. According to numerous investigations, these benefits are mostly related to phenols such as tyrosol and hydroxytyrosol and secoiridoid derivatives such as ligstroside, oleuropein, oleocanthal and oleacein. These compounds are present in low concentrations, and for some of them, standards are not commercially available, hampering studies on the mechanisms underlying their biological activity. In order to contribute to a better knowledge of the bioactivity of these compounds and their metabolites, they must be available with high purity and in sufficient amounts for the assays. Chemical synthesis has been considered a convenient way to obtain these compounds. This Review will focus on the synthesis of representative VOO compounds, namely, ligstroside, oleuropein, oleocanthal, oleacein and analogues.

New bifunctional 1,3-diamine organocatalysts derived from (+)-camphoric acid for asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroolefins.

Novel 1,3-diamine-derived bifunctional thiourea and squaramide organocatalysts were synthesized from (+)-camphoric acid. These catalysts were easily obtained in up to two to five synthetic steps, in a flexible approach that facilitates their structure variation. Their catalytic activity was examined in the asymmetric Michael addition of 1,3-dicarbonyl compounds to several trans-ß-nitrostyrenes. Yields up to 98% and enantiomeric excesses up to 74% and high diastereoselectivities when applicable (dr up to 93:7) were obtained in these reactions showing that 1,3-diamine-derived bifunctional thioureas are efficient organocatalysts.

A molecular test based on RT-LAMP for rapid, sensitive and inexpensive colorimetric detection of SARS-CoV-2 in clinical samples.

Until there is an effective implementation of COVID-19 vaccination program, a robust testing strategy, along with prevention measures, will continue to be the most viable way to control disease spread. Such a strategy should rely on disparate diagnostic tests to prevent a slowdown in testing due to lack of materials and reagents imposed by supply chain problems, which happened at the beginning of the pandemic. In this study, we have established a single-tube test based on RT-LAMP that enables the visual detection of less than 100 viral genome copies of SARS-CoV-2 within 30 min. We benchmarked the assay against the gold standard test for COVID-19 diagnosis, RT-PCR, using 177 nasopharyngeal RNA samples. For viral loads above 100 copies, the RT-LAMP assay had a sensitivity of 100% and a specificity of 96.1%. Additionally, we set up a RNA extraction-free RT-LAMP test capable of detecting SARS-CoV-2 directly from saliva samples, albeit with lower sensitivity. The saliva was self-collected and the collection tube remained closed until inactivation, thereby ensuring the protection of the testing personnel. As expected, RNA extraction from saliva samples increased the sensitivity of the test. To lower the costs associated with RNA extraction, we performed this step using an alternative protocol that uses plasmid DNA extraction columns. We also produced the enzymes needed for the assay and established an in-house-made RT-LAMP test independent of specific distribution channels. Finally, we developed a new colorimetric method that allowed the detection of LAMP products by the visualization of an evident color shift, regardless of the reaction pH.

An Efficient Synthesis of Optically Active [4-13C] Labelled Quorum Sensing Signal Autoinducer-2.

A new synthetic route for the quorum sensing signal Autoinducer-2 (AI-2) is described and used for the preparation of [4-13C]-AI-2 starting from [1-13C]-bromoacetic acid. The key step in this process was the enantioselective reduction of an intermediate ketone. This synthesis provides, selectively, both enantiomers of the labelled or unlabelled parent compound, (R) or (S)-4,5-dihydroxypentane-2,3-dione (DPD) and was used for an improved synthesis of [1-13C]-AI-2.

Canthaxanthin, a Red-Hot Carotenoid: Applications, Synthesis, and Biosynthetic Evolution.

Carotenoids are a class of pigments with a biological role in light capture and antioxidant activities. High value ketocarotenoids, such as astaxanthin and canthaxanthin, are highly appealing for applications in human nutraceutical, cosmetic, and animal feed industries due to their color- and health-related properties. In this review, recent advances in metabolic engineering and synthetic biology towards the production of ketocarotenoids, in particular the red-orange canthaxanthin, are highlighted. Also reviewed and discussed are the properties of canthaxanthin, its natural producers, and various strategies for its chemical synthesis. We review the de novo synthesis of canthaxanthin and the functional ß-carotene ketolase enzyme across organisms, supported by a protein-sequence-based phylogenetic analysis. Various possible modifications of the carotenoid biosynthesis pathway and the present sustainable cost-effective alternative platforms for ketocarotenoids biosynthesis are also discussed.

Synthesis and biological effects of small molecule enhancers for improved recombinant protein production in plant cell cultures.

Histone deacetylases are involved in chromatin remodelling and thus play a vital role in the epigenetic regulation of gene expression. HDAC inhibitors alter the acetylation status of histone and non-histone proteins to regulate various cellular events such as transcription. Novel HDAC inhibitors were designed and synthesised to promote higher levels of recombinant protein production in tobacco cell cultures. The effect of these chemical enhancers on the epigenetic profiles in plant cells has been evaluated by molecular docking, in vitro and in vivo studies. The addition of these novel enhancers led to an increase in histone H3 acetylation levels that promoted an increase in the accumulation levels of the recombinant protein in cell culture. These results can pave the way for the application of these enhancers to improve the production of high value products in plant cell based systems.

Synthesis of d-desthiobiotin-AI-2 as a novel chemical probe for autoinducer-2 quorum sensing receptors.

In processes regulated by quorum sensing (QS) bacteria respond to the concentration of autoinducers in the environment to engage in group behaviours. Autoinducer-2 (AI-2) is unique as it can foster interspecies communication. Currently, two AI-2 receptors are known, LuxP and LsrB, but bacteria lacking these receptors can also respond to AI-2. In this work, we present an efficient and reproducible synthesis of a novel chemical probe, d-desthiobiotin-AI-2. This probe binds both LuxP and LsrB receptors from different species of bacteria. Thus, this probe is able to bind receptors that recognise the two known biologically active forms of AI-2, presenting the plasticity essential for the identification of novel unknown AI-2 receptors. Moreover, a protocol to pull down receptors bound to d-desthiobiotin-AI-2 with anti-biotin antibodies has also been established. Altogether, this work highlights the potential of conjugating chemical signals to biotinylated derivatives to identify and tag signal receptors involved in quorum sensing or other chemical signalling processes.

The structural characterization of a glucosylglycerate hydrolase provides insights into the molecular mechanism of mycobacterial recovery from nitrogen starvation.

Bacteria are challenged to adapt to environmental variations in order to survive. Under nutritional stress, several bacteria are able to slow down their metabolism into a nonreplicating state and wait for favourable conditions. It is almost universal that bacteria accumulate carbon stores to survive during this nonreplicating state and to fuel rapid proliferation when the growth-limiting stress disappears. Mycobacteria are exceedingly successful in their ability to become dormant under harsh circumstances and to be able to resume growth when conditions are favourable. Rapidly growing mycobacteria accumulate glucosylglycerate under nitrogen-limiting conditions and quickly mobilize it when nitrogen availability is restored. The depletion of intracellular glucosyl-glycerate levels in Mycolicibacterium hassiacum (basonym Mycobacterium hassiacum) was associated with the up-regulation of the gene coding for glucosylglycerate hydrolase (GgH), an enzyme that is able to hydrolyse glucosylglycerate to glycerate and glucose, a source of readily available energy. Highly conserved among unrelated phyla, GgH is likely to be involved in bacterial reactivation following nitrogen starvation, which in addition to other factors driving mycobacterial recovery may also provide an opportunity for therapeutic intervention, especially in the serious infections caused by some emerging opportunistic pathogens of this group, such as Mycobacteroides abscessus (basonym Mycobacterium abscessus). Using a combination of biochemical methods and hybrid structural approaches, the oligomeric organization of M. hassiacum GgH was determined and molecular determinants of its substrate binding and specificity were unveiled.

The effect of new compounds in stabilizing downstream monoclonal antibody (mAb) process intermediates.

Determining the stability of downstream process (DSP) intermediates is an extremely important parameter used to maintain product quality attributes within their acceptance ranges. The IgG4 monoclonal antibody studied (mAb1) showed aggregation under acidic conditions, inhibiting the use of low pH treatment to inactivate endogenous retroviruses, and poor virus filtration performance. Both manufacturing steps are included in mAb DSP for viral clearance. The impact of several new compounds on the aggregation and stabilization of mAb1 in process intermediate pools encountered during these critical DSP steps was investigated. Results showed that, in the presence of a protein stabilizer at pH 3.2, 27% less aggregation was observed compared to controls, during the low pH treatment for viral inactivation. The impact of a novel protein stabilizer on virus filter throughput during mAb1 filtration was compared to L-arginine using an innovative high-throughput automation technique. Compared to control experiments without additives, conditions were found where a 70% increase in filter volumetric throughput was achieved in the presence of the novel stabilizer, and a 56% decrease in volumetric throughput observed with L-arginine. These findings present the possibility of using these novel compounds to stabilize proteins during DSP and permitting the use of platform DSP elements such as low pH treatment and high-throughput virus filtration to challenging and unstable proteins.

Biosynthesis of mycobacterial methylmannose polysaccharides requires a unique 1-O-methyltransferase specific for 3-O-methylated mannosides.

Mycobacteria are a wide group of organisms that includes strict pathogens, such as Mycobacterium tuberculosis, as well as environmental species known as nontuberculous mycobacteria (NTM), some of which-namely Mycobacterium avium-are important opportunistic pathogens. In addition to a distinctive cell envelope mediating critical interactions with the host immune system and largely responsible for their formidable resistance to antimicrobials, mycobacteria synthesize rare intracellular polymethylated polysaccharides implicated in the modulation of fatty acid metabolism, thus critical players in cell envelope assembly. These are the 6-O-methylglucose lipopolysaccharides (MGLP) ubiquitously detected across the Mycobacterium genus, and the 3-O-methylmannose polysaccharides (MMP) identified only in NTM. The polymethylated nature of these polysaccharides renders the intervening methyltransferases essential for their optimal function. Although the knowledge of MGLP biogenesis is greater than that of MMP biosynthesis, the methyltransferases of both pathways remain uncharacterized. Here, we report the identification and characterization of a unique S-adenosyl-l-methionine-dependent sugar 1-O-methyltransferase (MeT1) from Mycobacterium hassiacum that specifically blocks the 1-OH position of 3,3'-di-O-methyl-4α-mannobiose, a probable early precursor of MMP, which we chemically synthesized. The high-resolution 3D structure of MeT1 in complex with its exhausted cofactor, S-adenosyl-l-homocysteine, together with mutagenesis studies and molecular docking simulations, unveiled the enzyme's reaction mechanism. The functional and structural properties of this unique sugar methyltransferase further our knowledge of MMP biosynthesis and provide important tools to dissect the role of MMP in NTM physiology and resilience.

Synthesis and biological activity of a potent optically pure autoinducer-2 quorum sensing agonist.

Quorum sensing (QS) regulates population-dependent bacterial behaviours, such as toxin production, biofilm formation and virulence. Autoinducer-2 (AI-2) is to date the only signalling molecule known to foster inter-species bacterial communication across distantly related bacterial species. In this work, the synthesis of pure enantiomers of C4-propoxy-HPD and C4-ethoxy-HPD, known AI-2 analogues, has been developed. The optimised synthesis is efficient, reproducible and short. The (4S) enantiomer of C4-propoxy-HPD was the most active compound being approximately twice as efficient as (4S)-DPD and ten-times more potent than the (4R) enantiomer. Additionally, the specificity of this analogue to bacteria with LuxP receptors makes it a good candidate for clinical applications, because it is not susceptible to scavenging by LsrB-containing bacteria that degrade the natural AI-2. All in all, this study provides a new brief and effective synthesis of isomerically pure analogues for QS modulation that include the most active AI-2 agonist described so far.

Syntheses of the plant auxin conjugate 2-O-(indole-3-acetyl)-myo-inositol IAInos.

The plant hormone conjugate 2-O-(indole-3-acetyl)-myo-inositol (IAInos) has been selectively prepared for the first time by two routes from myo-inositol. One of the syntheses depended upon the construction of the 3-indoleacetyl group by a Fischer indole synthesis on an unreactive axial hydroxyl group, while the other via a direct acylation of the equatorially orientated hydroxy group created by conformational constraint of the cyclohexane ring. The latter synthesis produced IAInos in 5 steps and 29% overall yield.

Synthesis of New Sulfated and Glucuronated Metabolites of Dietary Phenolic Compounds Identified in Human Biological Samples.

(Poly)phenols are a large group of dietary compounds present in fruits and vegetables; their consumption is associated with health beneficial effects. After ingestion, (poly)phenols suffer extensive metabolization, and the identification of their metabolites is an emerging area, because these metabolites are considered the effective bioactive molecules in the human organism. However, a lack of commercially available standards has hampered the study of metabolite bioactivity and the exact structural confirmation in biological samples. New (poly)phenol metabolites previously identified in human samples after the intake of berry juice were chemically synthesized. Efficient chemical reactions were performed with moderate to excellent yields and selectivities. These new compounds could be used as standard chemicals for confirmation of the structure of metabolites in biological samples and will also allow mechanistic studies in cellular models.

Cranberry (poly)phenol metabolites correlate with improvements in vascular function: A double-blind, randomized, controlled, dose-response, crossover study.

SCOPE: Cranberries are rich in potentially bioactive (poly)phenols. The aim of this paper was to investigate whether cranberry juice intake can improve vascular function in healthy men in a dose- and time-dependent manner, and to understand which of the circulating (poly)phenol metabolites correlate with vascular effects. METHODS AND RESULTS: A double-blind randomized controlled crossover trial was conducted in ten healthy males. Flow-mediated dilation (FMD), blood pressure, pulse wave velocity and augmentation index were investigated at baseline, 1, 2, 4, 6, and 8 h post-consumption of cranberry juices containing 409, 787, 1238, 1534, and 1910 mg of total cranberry (poly)phenols (TP), and a control drink. Plasma (poly)phenol metabolites were analyzed by UPLC-Q-TOF MS using authentic standards. We observed dose-dependent increases in FMD at 1, 2, 4, 6, and 8 h with a peak at 4 h and maximal effects with juice containing 1238 mg TP. A total of 60 metabolites were quantified in plasma after cranberry consumption. Twelve (poly)phenol metabolites significantly correlated with the increases in FMD, including ferulic and caffeic acid sulfates, quercetin-3-O-ß-D-glucuronide and a γ-valerolactone sulfate. CONCLUSION: (Poly)phenols in cranberry juice can improve vascular function in healthy males and this is linked to the presence of specific newly identified plasma metabolites.

Identification and quantification of novel cranberry-derived plasma and urinary (poly)phenols.

Cranberries are a rich source of (poly)phenols, in particular proanthocyanidins, anthocyanins, flavonols, and phenolic acids. However, little is known about their bioavailability in humans. We investigated the absorption, metabolism, and excretion of cranberry (poly)phenols in plasma and urine of healthy young men after consumption of a cranberry juice (787 mg (poly)phenols). A total of 60 cranberry-derived phenolic metabolites were identified using UPLC-Q-TOF-MS analysis with authentic standards. These included sulfates of pyrogallol, valerolactone, benzoic acids, phenylacetic acids, glucuronides of flavonols, as well as sulfates and glucuronides of cinnamic acids. The most abundant plasma metabolites were small phenolic compounds, in particular hippuric acid, catechol-O-sulfate, 2,3-dihydroxybenzoic acid, phenylacetic acid, isoferulic acid, 4-methylcatechol-O-sulfate, α-hydroxyhippuric acid, ferulic acid 4-O-sulfate, benzoic acid, 4-hydroxyphenyl acetic acid, dihydrocaffeic acid 3-O-sulfate, and vanillic acid-4-O-sulfate. Some benzoic acids, cinnamic acids, and flavonol metabolites appeared in plasma early, at 1-2 h post-consumption. Others such as phenylacetic acids, benzaldehydes, pyrogallols, catechols, hippuric and dihydrocinnamic acid derivatives appear in plasma later (Tmax 4-22 h). The 24 h urinary recovery with respect to the amount of (poly)phenols consumed was 6.2%. Our extensive description of the bioavailability of cranberry (poly)phenols lays important groundwork necessary to start understanding the fate of these compounds in humans.

Octanoylation of early intermediates of mycobacterial methylglucose lipopolysaccharides.

Mycobacteria synthesize unique intracellular methylglucose lipopolysaccharides (MGLP) proposed to modulate fatty acid metabolism. In addition to the partial esterification of glucose or methylglucose units with short-chain fatty acids, octanoate was invariably detected on the MGLP reducing end. We have identified a novel sugar octanoyltransferase (OctT) that efficiently transfers octanoate to glucosylglycerate (GG) and diglucosylglycerate (DGG), the earliest intermediates in MGLP biosynthesis. Enzymatic studies, synthetic chemistry, NMR spectroscopy and mass spectrometry approaches suggest that, in contrast to the prevailing consensus, octanoate is not esterified to the primary hydroxyl group of glycerate but instead to the C6 OH of the second glucose in DGG. These observations raise important new questions about the MGLP reducing end architecture and about subsequent biosynthetic steps. Functional characterization of this unique octanoyltransferase, whose gene has been proposed to be essential for M. tuberculosis growth, adds new insights into a vital mycobacterial pathway, which may inspire new drug discovery strategies.