Influence of Nanoaggregation Routes on the Structure and Thermal Behavior of Multiple-Stimuli-Responsive Micelles from Block Copolymers of Oligo(ethylene glycol) Methacrylate and the Weak Acid [2-(Hydroxyimino)aldehyde]butyl Methacrylate.

In this work, we compare nanoaggregation driven by pH-induced micellization (PIM) and by the standard solvent displacement (SD) method on a series of pH-, light-, and thermosensitive amphiphilic block copolymers. Specifically, we investigate poly(HIABMA)-b-poly(OEGMA) and poly(HIABMA)-b-poly(DEGMA-r-OEGMA), where HIABMA = [(hydroxyimino)aldehyde]butyl methacrylate, OEGMA = oligo(ethylene glycol)methyl ether methacrylate, and DEGMA = di(ethylene glycol)methyl ether methacrylate. The weakly acidic HIA group (pKa ≈ 8) imparts stability to micelles at neutral pH, unlike most of the pH-responsive copolymers investigated in the literature. With SD, only some of our copolymers yield polymeric micelles (34-59 nm), and their thermoresponsivity is either poor or altogether absent. In contrast, PIM affords thermoresponsive, smaller micelles (down to 24 nm), regardless of the polymer composition. In some cases, cloud points are remarkably well defined and exhibit limited hysteresis. By combining turbidimetric, dyamic light scattering, and small-angle X-ray scattering measurements, we show that SD yields loose micelles with POEGMA segments partly involved in the formation of the hydrophobic core, whereas PIM yields more compact core-shell micelles with a well-defined PHIABMA core. We conclude that pH-based nanoaggregation provides advantages over block-selective solvation to obtain compact micelles exhibiting well-defined responses to external stimuli.

Unusually Chemoselective Photocyclization of 2-(Hydroxyimino)aldehydes to Cyclobutanol Oximes: Synthetic, Stereochemical, and Mechanistic Aspects.

Photocyclization of carbonyl compounds (known as the Norrish-Yang reaction) to yield cyclobutanols is, in general, accompanied by fragmentation reactions. The latter are predominant in the case of aldehydes so that secondary cyclobutanols are not considered accessible via the straightforward Norrish-Yang reaction. A noteworthy exception has been reported in our laboratory, where cyclobutanols bearing a secondary alcohol function were observed upon UV light irradiation of 2-(hydroxyimino)aldehydes (HIAs). This reaction is here investigated in detail by combining synthesis, spectroscopic data, molecular dynamics, and DFT calculations. The synthetic methodology is generally applicable to a series of HIAs, affording the corresponding cyclobutanol oximes (CBOs) chemoselectively (i.e., without sizable fragmentation side-reactions), diastereoselectively (up to >99:1), and in good to excellent yields (up to 95%). CBO oxime ether derivatives can be purified and diastereomers isolated by standard column chromatography. The mechanistic and stereochemical picture of this photocyclization reaction, as well as of the postcyclization E/Z isomerization of the oxime double bond is completed.

Anti-influenza A virus activity and structure-activity relationship of a series of nitrobenzoxadiazole derivatives.

Influenza viruses represent a major threat to human health and are responsible for seasonal epidemics, along with pandemics. Currently, few therapeutic options are available, with most drugs being at risk of the insurgence of resistant strains. Hence, novel approaches targeting less explored pathways are urgently needed. In this work, we assayed a library of nitrobenzoxadiazole derivatives against the influenza virus A/Puerto Rico/8/34 H1N1 (PR8) strain. We identified three promising 4-thioether substituted nitrobenzoxadiazoles (12, 17, and 25) that were able to inhibit viral replication at low micromolar concentrations in two different infected cell lines using a haemagglutination assay. We further assessed these molecules using an In-Cell Western assay, which confirmed their potency in the low micromolar range. Among the three molecules, 12 and 25 displayed the most favourable profile of activity and selectivity and were selected as hit compounds for future optimisation studies.

2-(Hydroxyimino)aldehydes: Photo- and Physicochemical Properties of a Versatile Functional Group for Monomer Design.

In the context of our research on stimuli-responsive polymers bearing the 2-(hydroxyimino)aldehyde (HIA) group, we have explored the photochemical behavior and physicochemical properties of a number of HIAs. Interpretation of the experimental data is supported by quantum mechanical calculations. HIAs are expected to undergo photoisomerization, chelate metal ions, yield hydrogen-bonded dimers or oligomers, exhibit relatively low pKa s, and form >C=NO. radicals through OH hydrogen abstraction or oxidation of the oximate ion. Besides the well-established E/Z oxime photoisomerism, we observed a Norrish-Yang cyclization resulting in cyclobutanol oximes, to our knowledge not previously described in the literature. The acidity, bond dissociation enthalpies, and electrochemical properties of the HIAs are compared with literature data of simple oximes. The results are discussed in relation to the many potential applications for HIAs, with emphasis on the synthesis of novel HIA-containing responsive polymers.

Influence of cultivation sites on sterol, nitrate, total phenolic contents and antioxidant activity in endive and stem chicory edible products.

Chicories produce a wide range of vegetables with important nutritional value. We determined the variation of sterol, total polyphenol, nitrate contents and antioxidant capacity (SC, TPC, NC, AC) in endive leaves and stem-chicory novel vegetables, cultivated in two Italian regions. Within a given area, the SC was similar in smooth- and curly leafed endives (106.3-176.0 mg/kg FW); sitosterol and stigmasterol were major fractions (45-56 versus 38-43%). The stem SC was independent of landrace (101.5-118.6 mg/kg FW); sitosterol prevailed on stigmasterol and fucosterol (73-76 versus 12-14% versus 8-9%); the latter reached 15.7 mg/kg FW, conferring value as potential antidiabetes food. The planting site affected the AC and TPC of endives (893.1-1571.4 µmTE/100 g FW, 30.8-76.1 GAE100/g FW) and chicory stems (729.8-1152.5 µmTE/100 g FW; 56.2-124.4 GAE100/g FW), while the NC was recurrently below dangerous thresholds. PCA showed that environment was the major cause of variation, though it modestly affected these parameters.

First-in-Class Selective Inhibitors of the Lysine Acetyltransferase KAT8.

KAT8 is a lysine acetyltransferase primarily catalyzing the acetylation of Lys16 of histone H4 (H4K16). KAT8 dysregulation is linked to the development and metastatization of many cancer types, including non-small cell lung cancer (NSCLC) and acute myeloid leukemia (AML). Few KAT8 inhibitors have been reported so far, none of which displaying selective activity. Based on the KAT3B/KDAC inhibitor C646, we developed a series of N-phenyl-5-pyrazolone derivatives and identified compounds 19 and 34 as low-micromolar KAT8 inhibitors selective over a panel of KATs and KDACs. Western blot, immunofluorescence, and CETSA experiments demonstrated that both inhibitors selectively target KAT8 in cells. Moreover, 19 and 34 exhibited mid-micromolar antiproliferative activity in different cancer cell lines, including NSCLC and AML, without impacting the viability of nontransformed cells. Overall, these compounds are valuable tools for elucidating KAT8 biology, and their simple structures make them promising candidates for future optimization studies.

Sirtuin modulators: past, present, and future perspectives.

Sirtuins are NAD+-dependent protein lysine deacylase and mono-ADP ribosylases present in both prokaryotes and eukaryotes. The sirtuin family comprises seven isoforms in mammals, each possessing different subcellular localization and biological functions. Sirtuins have received increasing attention in the past two decades given their pivotal functions in a variety of biological contexts, including cytodifferentiation, transcriptional regulation, cell cycle progression, apoptosis, inflammation, metabolism, neurological and cardiovascular physiology and cancer. Consequently, modulation of sirtuin activity has been regarded as a promising therapeutic option for many pathologies. In this review, we provide an up-to-date overview of sirtuin biology and pharmacology. We examine the main features of the most relevant inhibitors and activators, analyzing their structure-activity relationships, applications in biology, and therapeutic potential.

Ready-to-eat vegetables production with low-level water chlorination. An evaluation of water quality, and of its impact on end products.

INTRODUCTION: We evaluated the microbiological impact of low-level chlorination (1 ppm free chlorine) on the production of ready-to-eat (RTE) vegetables by monitoring the microbiological quality of irrigation and processing water in two production plants over a 4-season period, as well as the microbiological quality of unprocessed vegetables and RTE product. Water samples were also characterized in terms of some chemical and physico-chemical parameters of relevance in chlorination management. MATERIALS AND METHODS: Both producers use water with maximum 1 ppm free chlorine for vegetables rinsing, while the two processes differ by the number of washing cycles. RESULTS AND CONCLUSIONS: Salmonella spp and Campylobacter spp were detected once in two different irrigation water samples out of nine from one producer. No pathogens were found in the vegetable samples. As expected, the procedure encompassing more washing cycles performed slightly better in terms of total mesophilic count (TMC) when comparing unprocessed and RTE vegetables of the same batch. However, data suggest that low-level chlorination may be insufficient in preventing microbial build-up in the washing equipment and/or batch-to batch cross-contamination.

First synthesis of a polysaccharide-supported lignin model compound and study of its oxidation promoted by lignin peroxidase.

Veratrylchitosan, a polysaccharide-supported lignin model compound, has been synthesised by covalently attaching 3-(3,4-dimethoxybenzyloxy)propionic acid to the polysaccharide chitosan through an amide linkage. When this polymer was used as a substrate in the oxidation promoted by lignin peroxidase (LiP), significant decomposition of the lignin model resulted in the formation of veratraldehyde. The oxidation mechanism involves an initial transfer of one electron from chitosan to the active species of LiP (LiP I) followed by C(alpha)-H deprotonation of an aromatic cation radical. A benzylic radical is then formed which is further oxidised to a benzyl cation. Reaction with water and hydrolysis of the hemiacetal then lead to veratraldehyde formation. An increase in the yields of the oxidation product is observed in the presence of the mediator 2-chloro-1,4-dimethoxybenzene, thus indicating that a more efficient degradation results from the transfer of an electron from the polymer to the radical cation of the mediator.

First evidence of catalytic mediation by phenolic compounds in the laccase-induced oxidation of lignin models.

The sulfonephthalein indicator, phenol red, exhibits an unusually slow rate of oxidation by laccase from Poliporus pinsitus, in spite of the fact that it is a phenol and therefore a natural substrate for this phenoloxidase enzyme. Nevertheless, after prolonged exposure to laccase (24 h) phenol red is oxidized by more than 90%. We found that phenol red, which can be oxidatively converted into a resonance-stabilized phenoxy radical, performs as a mediator in the laccase-catalyzed oxidation of a nonphenolic substrate (4-methoxybenzyl alcohol) and also of a hindered phenol (2,4,6-tri-tert-butylphenol). In particular, phenol red was found to be at least 10 times more efficient than 3-hydroxyanthranilate (a reported natural phenolic mediator of laccase) in the oxidation of 4-methoxybenzyl alcohol. Other phenols, which do not bear structural analogies to phenol red, underwent rapid degradation and did not perform as laccase mediators. On the other hand, several variously substituted sulfonephthaleins, of different pK2 values, mediated the laccase catalysis, the most efficient being dichlorophenol red, which has the lowest pK2 of the series. The mediating efficiency of phenol red and dichlorophenol red was found to be pH dependent, as was their oxidation Ep value (determined by cyclic voltammetry). We argue that the relative abundance of the phenoxy anion, which is easier to oxidize than the protonated phenol, may be one of the factors determining the efficiency of a phenolic mediator, together with its ability to form relatively stable oxidized intermediates that react with the desired substrate before being depleted in undesired routes.

Oxidation of phenols by laccase and laccase-mediator systems.

To investigate how solubility and steric issues affect the laccase-catalysed oxidation of phenols, a series of oligomeric polyphenol compounds, having increasing size and decreasing solubility in water, was incubated with laccase. The extent of substrate conversion, and the nature of the products formed in buffered aqueous solutions, were compared to those obtained in the presence of an organic cosolvent, and also in the presence of two mediating species, i.e. N-hydroxyphthalimide (HPI) and 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO). This approach showed not only an obvious role of solubility, but also a significant role of the dimension of the substrate upon the enzymatic reactivity. In fact, reactivity decreases as substrate size increases even when solubility is enhanced by a cosolvent. This effect may be ascribed to limited accessibility of encumbered substrates to the enzyme active site, and can be compensated through the use of the appropriate mediator. While TEMPO was highly efficient at enhancing the reactivity of large, less soluble substrates, HPI proved less effective. In addition, whereas the laccase/HPI system afforded the same products as laccase alone, the use of TEMPO provided a different product with high specificity. These results offer the first evidence of the role of 'oxidation shuttles' that the mediators of laccase may have, but also suggest two promising routes towards an environmentally friendly process for kraft pulp bleaching: (a) the identification of mediators which, once oxidized by laccase, are able to target strategic functional groups present in lignin, and (b) the introduction of those strategic functional groups in an appropriate pretreatment.

Determination of laccase activity in mixed solvents: comparison between two chromogens in a spectrophotometric assay.

Spectrophotometric determination of laccase activity with ABTS acting as chromogen yields exceedingly low values whenever conducted in a water-organic mixed solvent. Nevertheless, there is firm evidence that laccase is able to oxidize substrates such as phenols and amines quantitatively in these mixed solvents. We show that the apparently small rate of ABTS oxidation by laccase in a mixed solvent, such as buffered water-dioxane 1:1, is not amenable to the denaturation of laccase but rather to the decreased stability of ABTS(.+). We propose HAA as a more reliable chromogen for the determination of laccase activity in mixed solvents.