Kalanchoe pinnata (Lam.) Pers. Leaf ethanolic extract exerts selective anticancer activity through ROS-induced apoptotic cell death in human cancer cell lines.

BACKGROUND: The leaves of Kalanchoe pinnata (Lam.) Pers. (K. pinnata), a succulent plant native to tropical regions, are used as a medicinal alternative against cancer in several countries worldwide; however, its therapeutic potential to fight cancer has been little addressed. In this study, we analyzed the phytochemical content, antioxidant capacity, and selectivity of K. pinnata leaf ethanolic extract against different human cancer cell lines in vitro. METHODOLOGY: This study subjected the ethanolic extract to enzymatic assays to quantify the phytochemical content (phenolics, flavonoids, and anthraquinones) and its radical scavenging and iron-reducing capacities. Also, the phytoconstituents and major phenolic compounds present in the extract's subfractions were identified by GC-MS, HPLC, and NMR. Human cancer (MCF-7, PC-3, HT-29) and normal colon (CoN) cell lines were treated with different concentrations of K. pinnata leaf ethanolic extract, and the changes in cell proliferation (sulforhodamine B assay), caspases activity (FITC-VAD-FMK reporter), mitochondrial membrane potential (MMP, rhodamine 123 assay), chromatin condensation/fragmentation (Hoechst 33342 stain), and ROS generation (DCFH2 probe assay) were assessed. RESULTS: The results showed that the K. pinnata leaf ethanolic extract is rich in phytoconstituents with therapeutic potential, including phenols (quercetin and kaempferol), flavonoids, fatty acid esters (34.6% of the total composition), 1- triacontanol and sterols (ergosterol and stigmasterol, 15.4% of the total composition); however, it presents a poor content of antioxidant molecules (IC50 = 27.6 mg/mL for H2O2 scavenging activity vs. 2.86 mg/mL in the case of Trolox). Notably, the extract inhibited cell proliferation and reduced MMP in all human cell lines tested but showed selectivity for HT-29 colon cancer cells compared to CoN normal cells (SI = 8.4). Furthermore, ROS generation, caspase activity, and chromatin condensation/fragmentation were augmented significantly in cancer-derived cell lines, indicating a selective cytotoxic effect. CONCLUSION: These findings reveal that the K. pinnata leaf ethanolic extract contains several bioactive molecules with therapeutic potential, capable of displaying selective cytotoxicity in different human cancer cell lines.

Synthesis of silver-palladium Janus nanoparticles using co-sputtering of independent sources: experimental and theorical study.

Janus-type nanoparticles are important because of their ability to combine distinct properties and functionalities in a single particle, making them extremely versatile and valuable in various scientific, technological, and industrial applications. In this work, bimetallic silver-palladium Janus nanoparticles were obtained for the first time using the inert gas condensation technique. In order to achieve this, an original synthesis equipment built by Mantis Ltd. was modified by the inclusion of an additional magnetron in a second chamber, which allowed us to use two monometallic targets to sputter the two metals independently. With this arrangement, we could find appropriate settings at room temperature to promote the synthesis of bimetallic Janus nanoparticles. The structural properties of the resulting nanoparticles were investigated by transmission electron microscopy (TEM), and the chemical composition was analyzed by TEM energy dispersive spectroscopy (TEM-EDS), which, together with structural analysis, confirmed the presence of Janus-type nanostructures. Results of molecular dynamics and TEM simulations show that the differences between the crystalline structures of the Pd and Ag regions observed in the TEM micrographs can be explained by small mismatches in the orientations of the two regions of the particle. A density functional theory structural aims to understand the atomic arrangement at the interface of the Janus particle.

Potent Anthelmintic Activity of Chalcones Synthesized by an Effective Green Approach.

There is currently an urgent need for new anthelmintic agents due to increasing resistance to the limited available drugs. The chalcone scaffold is a privileged structure for developing new drugs and has been shown to exhibit potential antiparasitic properties. We synthesized a series of chalcones via Claisen-Schmidt condensation, introducing a novel recoverable catalyst derived from biochar obtained from the pyrolysis of tree pruning waste. Employing microwave irradiation and a green solvent, this approach demonstrated significantly reduced reaction times and excellent compatibility with various functional groups. The result was the generation of a library of functionalized chalcones, exhibiting exclusive (E)-selectivity and high to excellent yields. The chalcone derivatives were evaluated on the free-living nematode Caenorhabditis elegans. The chalcone scaffold, along with two derivatives incorporating a methoxy substituent in either ring, caused a concentration-dependent decrease of worm motility, revealing potent anthelmintic activity and spastic paralysis not mediated by the nematode levamisole-sensitive nicotinic receptor. The combination of both methoxy groups in the chalcone scaffold resulted in a less potent compound causing worm hypermotility at the short term, indicating a distinct molecular mechanism. Through the identification of promising drug candidates, this work addresses the demand for new anthelmintic drugs while promoting sustainable chemistry.

Effect of Obturation Techniques on the Quality of Root Canal Fillings: A Systematic Review and Meta-analysis of in Vitro Studies.

Introduction: The current study aimed to compare the quality of root canal obturation performed with cold lateral condensation with other obturation techniques. Materials and Methods: Diverse Search was conducted using six electronic/academic databases following PICOS (i.e. population, intervention, control, outcomes, and study design) strategy: (P) Extracted mature permanent teeth; (I) Obturation techniques except for cold lateral condensation; (C) Cold lateral condensation tyechnique; (O) Quality of root canal obturation; and (S) In vitro studies assessing parameters using micro-computed tomography. The statistical method used for the meta-analyses was the "inverse variance DerSimonian-Laird test". The heterogeneity data was calculated using the T2, Cochran Q test, and I2 statistics. Results: Fifteen studies were included for the final analysis; one had a low risk of bias, eight a moderate risk, and six a high risk of bias. Ten studies were selected for meta-analyses; three studies comparing cold lateral condensation with carrier-based gutta-percha techniques [P=0.96; mean difference (MD)=-0.02; confidence interval (CI): (-0.77, 0.73); I2=21%]; three comparing cold lateral condensation with single-cone techniques [P=0.75; MD=-0.39; CI: (-2.77, 1.99); I2=92%]; two comparing cold lateral condensation and thermo-plasticized injectable techniques [P=0.37; MD=5.91; CI: (-7.13,18.94); I2=99%]; and five comparing cold lateral condensation with warm vertical condensation techniques [P<0.0001; MD=5.29; CI=(2.84, 7.74); I2=92%]. The overall effect reported significant results [P=0.0003; MD=2.69; CI=(1.23, 4.16); I2=96%]; favoring fewer voids and gaps for the other used obturation techniques. Conclusions: Cold lateral condensation and single-cone techniques presented no statistical differences. Nonetheless, Warm vertical condensation technique had better results compared to cold lateral condensation.

Phenolic chalcones as agents against Trichomonas vaginalis.

Trichomonas vaginalis, a flagellated and anaerobic protozoan, is a causative agent of trichomoniasis. This disease is among the world's most common non-viral sexually transmitted infection. A single class drug, nitroimidazoles, is currently available for the trichomoniasis treatment. However, resistant isolates have been identified from unsuccessfully treated patients. Thus, there is a great challenge for a discovery of innovative anti-T. vaginalis agents. As part of our ongoing search for antiprotozoal chalcones, we designed and synthesized a series of 21 phenolic chalcones, which were evaluated against T. vaginalis trophozoites. Structure-activity relationship indicated hydroxyl group plays a role key in antiprotozoal activity. 4'-Hydroxychalcone (4HC) was the most active compound (IC50 = 27.5 µM) and selected for detailed bioassays. In vitro and in vivo evaluations demonstrated 4HC was not toxic against human erythrocytes and Galleria mellonella larvae. Trophozoites of T. vaginalis were treated with 4HC and did not present significant reactive oxygen species (ROS) accumulation. However, compound 4HC was able to increase ROS accumulation in neutrophils coincubated with T. vaginalis. qRT-PCR Experiments indicated that 4HC did not affect the expression of pyruvate:ferredoxin oxidoreductase (PFOR) and ß-tubulin genes. In silico simulations, using purine nucleoside phosphorylase of T. vaginalis (TvPNP), corroborated 4HC as a promising ligand. Compound 4HC was able to establish interactions with residues D21, G20, M180, R28, R87 and T90 through hydrophobic interactions, π-donor hydrogen bond and hydrogen bonds. Altogether, these results open new avenues for phenolic chalcones to combat trichomoniasis, a parasitic neglected infection.

Biochar-MgO from Soursop Seeds in the Production of Biofuel Additive Intermediates.

The conversion of residual biomass from fruit seeds into biochar can be achieved using MgCl2 as an activating agent and calcining at 700 °C. The resulting MgO-biochars were employed in the aldol condensation reaction between furfural and acetone. This reaction is essential as the first step in the obtention of biofuels derived from biomass. The biochars were characterized through various physicochemical techniques, revealing that the presence of MgO nanoparticles deposited on the carbon surface modifies the structural and acidic-basic properties of the carbonaceous materials with a graphitic structure. The biochar with a surface content of MgO of 0.34 % w/w enables the achievement of 100 % of selectivity towards 4-(2-furanyl)-3-buten-2-one (I) with quantitative conversions under optimized conditions. This property highlights the potential of using this type of biochar, commonly used for CO2 capture, as a versatile acidic-basic catalyst, thereby introducing a novel approach to sustainable chemistry.

Synthesis, NMR characterization and cytotoxic activity of hybrid spirostanic sapogenins-estradiol dimers.

Four hybrid steroid dimers were obtained by BF3·Et2O-catalyzed aldol condensation of acetylated steroid sapogenins with 2-formyl-estradiol diacetate. The structures of the obtained dimers were unambiguously established by NMR. The hybrid dimers 9a (IC50 18.37 µM) and 9c (IC50 9.4 µM) with the 5α configuration at the A/B rings junction showed the higher cytotoxicity against HeLa, with selectivity index of 4.36 and 11.8 respectively. The presence of a carbonyl function at position C-12 produced the highest cytotoxic effect, which is in line with our previous reports.

Extracellular vesicle-localized miR-203 mediates neural crest-placode communication required for trigeminal ganglia formation.

While interactions between neural crest and placode cells are critical for the proper formation of the trigeminal ganglion, the mechanisms underlying this process remain largely uncharacterized. Here, we show that the microRNA-(miR)203, whose epigenetic repression is required for neural crest migration, is reactivated in coalescing and condensing trigeminal ganglion cells. Overexpression of miR-203 induces ectopic coalescence of neural crest cells and increases ganglion size. Reciprocally, loss of miR-203 function in placode, but not neural crest, cells perturbs trigeminal ganglion condensation. Demonstrating intercellular communication, overexpression of miR-203 in the neural crest in vitro or in vivo represses a miR-responsive sensor in placode cells. Moreover, neural crest-secreted extracellular vesicles (EVs), visualized using pHluorin-CD63 vector, become incorporated into the cytoplasm of placode cells. Finally, RT-PCR analysis shows that small EVs isolated from condensing trigeminal ganglia are selectively loaded with miR-203. Together, our findings reveal a critical role in vivo for neural crest-placode communication mediated by sEVs and their selective microRNA cargo for proper trigeminal ganglion formation.

New Ultrasonic Tip for Root Canal Filling of the Mesial Canals of Mandibular Molars with Isthmus: A Laboratory Evaluation Using Computed Microtomography.

INTRODUCTION: The obturation quality of the mandibular molar mesial canals and isthmuses with two thermoplastic techniques, ultrasonic vertical condensation (UVC) and continuous wave of condensation (CWC), was evaluated using computed microtomography (µCT). METHODS: Thirty-six human mandibular molars had been previously scanned and analyzed using µCT for mesial roots with morphologically similar isthmuses for this study. Coronal access and confirmation of foraminal patency were performed, and the actual length of the teeth was established using a clinical microscope (40X magnification). The canals were prepared using ProTaper Gold instruments up to #F3, with 2.5% sodium hypochlorite as the irrigant solution, followed by a passive ultrasonic irrigation protocol. The specimens were randomly divided into the UVC and CWC groups based on the obturation technique to be used. Obturation was performed with #F3 gutta-percha cones cemented using AH Plus Jet sealer. The µCT scans were performed after 15 days, and the images were evaluated by a calibrated examiner blinded to the experimental groups to determine the filling rate of the entire canal area, including the main canal and isthmus. Student's t-test was used for statistical analysis; P values ≤0.05 were considered significant. RESULTS: Neither of the thermoplastic obturation techniques achieved complete filling of the canals (86.3% for UVC and 91.4% for CWC), with a statistically significant difference between them (P = .029). CONCLUSIONS: Under the conditions of the study, it can be concluded that none of the techniques completely filled the canal/isthmus of the mandibular molars; however, the CWC exhibited better performance.

Synthesis of bis(ylidene) cyclohexanones and their antifungal activity against selected plant pathogenic fungi.

Botrytis cinerea, Rhizoctonia solani and Hemileia vastatrix are three species of phytopathogenic fungi behind major crop losses worldwide. These have been selected as target models for testing the fungicide potential of a series of bis(ylidene) cyclohexanones. Although some compounds of this chemical class are known to have inhibitory activity against human pathogens, they have never been explored for the control of phytopathogens until now. In the present work, bis(ylidene) cyclohexanones were synthesized through simple, fast and low-cost base- or acid-catalyzed aldol condensation reaction and tested in vitro against B. cinerea, R. solani and H. vastatrix. bis(pyridylmethylene) cyclohexanones showed the highest activity against the target fungi. When tested at 200 nmol per mycelial plug against R. solani., these compounds completely inhibited the mycelial growth, and the most active bis(pyridylmethylene) cyclohexanone compound had an IC50 of 155.5 nmol plug-1. Additionally, bis(pyridylmethylene) cyclohexanones completely inhibited urediniospore germination of H. vastatrix, at 125 µmol L-1. The most active bis(pyridylmethylene) cyclohexanone had an IC50 value of 4.8 µmol L-1, which was estimated as approximately 2.6 times lower than that found for the copper oxychloride-based fungicide, used as control. Additionally, these substances had a low cytotoxicity against the mammalian Vero cell line. Finally, in silico calculations indicated that these compounds present physicochemical parameters regarded as suitable for agrochemicals. Bis(ylidene) cyclohexanones may constitute promising candidates for the development of novel antifungal agents for the control of relevant fungal diseases in agriculture.

The Roles of Histone Post-Translational Modifications in the Formation and Function of a Mitotic Chromosome.

During mitosis, many cellular structures are organized to segregate the replicated genome to the daughter cells. Chromatin is condensed to shape a mitotic chromosome. A multiprotein complex known as kinetochore is organized on a specific region of each chromosome, the centromere, which is defined by the presence of a histone H3 variant called CENP-A. The cytoskeleton is re-arranged to give rise to the mitotic spindle that binds to kinetochores and leads to the movement of chromosomes. How chromatin regulates different activities during mitosis is not well known. The role of histone post-translational modifications (HPTMs) in mitosis has been recently revealed. Specific HPTMs participate in local compaction during chromosome condensation. On the other hand, HPTMs are involved in CENP-A incorporation in the centromere region, an essential activity to maintain centromere identity. HPTMs also participate in the formation of regulatory protein complexes, such as the chromosomal passenger complex (CPC) and the spindle assembly checkpoint (SAC). Finally, we discuss how HPTMs can be modified by environmental factors and the possible consequences on chromosome segregation and genome stability.

Counterion condensation theory for finite polyelectrolyte and salt concentrations.

In the present work we analyze the physical fundamentals of Manning's counterion condensation using his charged line model in a simple salt solution. We extend the theory for the cases of finite saline concentration and polymeric concentration tending to zero and the case of both finite concentrations. To find the equilibrium between the phases of free and condensed counterions, besides minimizing the free energy, we deduce an auxiliary equation to determine the two characteristic parameters of the theory, the fraction of condensed counterions and the volume of condensation. We compare the obtained results in the present work for only one infinite charged line with the ones of counterion condensation theory by Schurr and Fujimoto. We find that the linear density of critical charge depends on the concentration of added salt and takes values higher than one, instead of the unitary value predicted by Manning. We obtain the equations by the activity and osmotic coefficients in function of the critical charge density. We compare them with the corresponding equations by Manning for these parameters. We extend the counterion condensation theory to solutions of linear polyelectrolytes for finite saline and polymeric concentrations using a cell model. We modify the electrostatic contribution to the Gibbs energy adding, to the traditional one calculated by Manning, the energy excess due to the macroion present in a cylindrical cell. We apply the theory to obtain the osmotic coefficient and we compare our results with experimental data of DNA osmotic coefficient and with theoretical adjustment using the Poisson-Boltzmann equation.

Benzothiazoles from Condensation of o-Aminothiophenoles with Carboxylic Acids and Their Derivatives: A Review.

Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use in the synthesis of a great variety of biologically active compounds. Heterocyclic compounds are widely found in nature and are essential for life. Among these, some natural nitrogen containing heterocyclic compounds have been used as chemotherapeutic agents. Their attachment to sugar molecules either as thioglycosides or as nucleosides analogues plays an important role in vital biological processes as well as in synthetic organic chemistry. Molecules containing benzothiazole (BT) nuclei are of this interesting class of compounds because some of them have been found to have a wide variety of biological activities. In this sense, we selected this topic to review and to then summarize the procedures related to the condensation reactions of o-aminothiophenoles (ATPs) as well as their disulfides with carboxylic acids, esters, orthoesters, acyl chlorides, amides, and nitriles. The condensation reactions with carbon dioxide (CO2) are included. Conventional methods with the use of acid and metal catalysts as well as recent green techniques, such as microwave irradiation, the use of ionic liquids, and ultrasound (US) chemistry, which have proven to have many advantages, were found in the review.

Design, synthesis, and molecular docking study of novel quinoline-based bis-chalcones as potential antitumor agents.

A novel series of quinoline-based symmetrical and unsymmetrical bis-chalcones was synthesized via a Claisen-Schmidt condensation reaction between 3-formyl-quinoline/quinolone derivatives with acetone or arylidene acetones, respectively, by using KOH/MeOH/H2 O as a reaction medium. Twelve of the obtained compounds were evaluated for their in vitro cytotoxic activity against 60 different human cancer cell lines according to the National Cancer Institute protocol. Among the screened compounds, the symmetrical N-butyl bis-quinolinyl-chalcone 14g and the unsymmetrical quinolinyl-bis-chalcone 17o bearing a 7-chloro-substitution on the N-benzylquinoline moiety and 4-hydroxy-3-methoxy substituent on the phenyl ring, respectively, exhibited the highest overall cytotoxicity against the evaluated cell lines with a GI50 range of 0.16-5.45 µM, with HCT-116 (GI50 = 0.16) and HT29 (GI50 = 0.42 µM) (colon cancer) representing best-case scenarios. Notably, several GI50 values for these compounds were lower than those of the reference drugs doxorubicin and 5-FU. Docking studies performed on selected derivatives yielded very good binding energies in the active site of proteins that participate in key carcinogenic pathways.

A Comparative Evaluation of Endodontically Treated Root Canals Obturated Using Gutta-percha with Two Different Protocols: An In-vitro Study.

OBJECTIVE: The aim of this article is to evaluate the quality of filling in endodontically treated root canals using the lateral condensation technique and modified lateral condensation technique. MATERIALS AND METHODS: Thirty-two single-rooted teeth were divided into two groups that were assigned by simple randomization according to the filling technique. Once the endodontic treatment was performed, a periapical radiograph was taken to assess the quality according to the radiographic density and tomography was taken to evaluate the quality according to the tomographic volume of spaces, compared with the post-preparation biomechanical tomography. Finally, we performed a statistical analysis (Student's t-test) to evaluate whether there were differences between the types of filling. RESULTS: Radiographic radiodensity was 182.89 ± 9.81 and 186.72 ± 6.97 HU for teeth treated with the lateral condensation technique and modified lateral condensation technique, respectively. The void volume was 3.75 ± 2.35 and 2.43 ± 1.18 mm3 for teeth treated with the lateral condensation technique and modified lateral condensation technique, respectively. CONCLUSION: No significant differences were found between the techniques for both filling quality parameters.

Sperm head morphometry and chromatin condensation are in constant change at seminiferous tubules, epididymis, and ductus deferens in bulls.

The aim of this study was to evaluate the sperm head morphometry and chromatin condensation at different regions of the reproductive tract in bulls. Sperm smears of seminiferous tubules (ST), epididymis head (EH), body (EB), and tail (ET), and ductus deferens (DD) were stained with toluidine blue. Afterwards, the sperm head morphometry and chromatin alteration types were evaluated by a computational image analysis. Overall, spermatozoa of ST had lower (P < 0.05) area (A), perimeter (P), width (W), length (L), ellipticity (E), and Fourier harmonics (F0, F1, and F2). The chromatin decondensation (CD) and heterogeneity (CH) were higher (P < 0.05) in the ST region and decreased (P < 0.0001) during the migration along the reproductive tract (ST - DD direction). Considering the factors extracted (Factors 1 and 2) by the principal component analysis, the parameters A, P, W, L, and F0 were responsible for ∼36% of the Factor 1, while the E, F0, F1, and anterior-posterior symmetry (APS) contributed ∼27% to Factor 2. Both, CD and CH were associated with Factor 1 in the EH and ET regions and Factor 2 in the ST. Also, a well-defined difference between sperm heads collected from the ST and DD regions was observed by canonical analysis. The distribution of each chromatin alteration type was recorded. The proportion of normal sperm was lower (P < 0.05) in ST compared to other regions. Moreover, the chromatin influenced the morphometry and sperm heads with whole chromatin alteration type showed a smaller (P < 0.05) A, P, W, L, and E. In summary, the epididymal maturation is important for chromatin compaction and final morphometry of the sperm head. Also, the identification and quantification of the sperm chromatin condensation in different regions of reproductive tract can be used as potential biomarkers to predict the fertility in bulls.

In-situ extraction of depolymerization products by membrane filtration against lignin condensation.

Catalytic depolymerization of lignin is a challenging process due to competitive repolymerization reactions. In this paper, the oxidative depolymerization of lignin was catalyzed by a commercial laccase both in a batch experiment and in a membrane bioreactor using the same catalytic conditions. The membrane bioreactor was previously optimized to reach high permeation flux (25 L.h-1.m-2) during lignin diafiltration. While the lignin was exclusively condensed in the batch experiment leading to high molecular weight macromolecules (from 9 to 16 kDa), its depolymerization was effective in the bioreactor producing fragments of less than 1 kDa thanks to the in-situ extraction of the reaction products. This paper demonstrates that the reactor configuration is playing an essential role in triggering or preventing lignin condensation. It also reports the first proof-of-concept demonstrating that in-situ membrane extraction of the reactive fragments of lignin from the bulk medium can be useful against detrimental repolymerization reactions.

Synthesis of Knoevenagel Adducts Under Microwave Irradiation and Biocatalytic Ene-Reduction by the Marine-Derived Fungus Cladosporium sp. CBMAI 1237 for the Production of 2-Cyano-3-Phenylpropanamide Derivatives.

The organic synthesis has been driven by the need of sustainable processes, which also requires efficiency and cost-effectiveness. In this work, we described the synthesis of nine Knoevenagel adducts between cyanoacetamide and aromatic aldehydes ((E)-2-cyano-3-(phenyl)acrylamide derivatives), employing triethylamine as catalyst under microwave irradiation in 30 min with excellent yields (93-99% yield). Then, these adducts were employed in the C-C double bond bioreduction by the marine-derived fungus Cladosporium sp. CBMAI 1237 for obtention of 2-cyano-3-phenylpropanamide derivatives in mild conditions and short reaction time for a whole-cells reduction (phosphate buffer pH 7.0, 32 °C, 130 rpm, 8 h) with good yields (48-90%). It is important to emphasize that the experimental conditions, especially the reaction time, should be carefully evaluated for the obtention of high yields. Since a biodegradation process consumed the obtained product in extended periods, probably due to the use of the substrate as carbon and nitrogen source. This approach showed that the use of coupled and greener catalysis methods such as microwave irradiation and biocatalytic reduction, which employs unique biocatalysts like marine-derived fungi, can be an interesting tool for the obtention of organic molecules.

Study of the polyribosyl-ribitol-phosphate precipitation mechanism by salts and organic solvents.

Precipitation has been widely applied to purification and fractionation of biological macromolecules. Several physical-chemical factors contribute to the destabilization of those solutions, such as the nature of solvent employed, presence of salts, temperature, and concentration of the macromolecule. In the case of charged biopolymers, electrostatic forces are the major contributors to their stability in solution. However, the role of each variable and the exact mechanism of precipitation are not completely understood yet. The aim of this work was to study the precipitation of polyribosyl-ribitol-phosphate (PRP, a linear homogeneous anionic biopolymer) in presence of salts and non-solvents, in order to contribute to the elucidation of its precipitation mechanism. The solvents tested (acetone, ethanol, and isopropanol) presented distinct dielectric constants. The salts used (NH4Cl, NaCl, KCl, MgCl2, and CaCl2) differ by their cations. For each salt concentration, the solvent fraction that induces precipitation was identified and the dielectric constant of the bulk solution was calculated. Precipitation always occurred at well-defined combinations of solvents and salts. At low concentration of monovalent salts, there was a linear correlation between the logarithm of the salt concentration and the inverse of the medium dielectric constant at a defined precipitation point. This is a strong indication that the stability of the solution depends almost exclusively on the balance of electrostatic forces. This behavior is compatible with the DLVO modeling of colloidal systems. When divalent salts were used, low concentrations of the counterion were sufficient to induce precipitation, due to a phenomenon called ionic condensation. Apparently, PRP precipitates when around 90% of its charges are neutralized, value that is similar to charge neutralization for DNA precipitation.

Enantioselective ene-reduction of E-2-cyano-3-(furan-2-yl) acrylamide by marine and terrestrial fungi and absolute configuration of (R)-2-cyano-3-(furan-2-yl) propanamide determined by calculations of electronic circular dichroism (ECD) spectra.

This work reports the green organic chemistry synthesis of E-2-cyano-3(furan-2-yl) acrylamide under microwave radiation (55 W), as well as the use of filamentous marine and terrestrial-derived fungi, in the first ene-reduction of 2-cyano-3-(furan-2-yl) acrylamide to (R)-2-cyano-3-(furan-2-yl)propanamide. The fungal strains screened included Penicillium citrinum CBMAI 1186, Trichoderma sp. CBMAI 932 and Aspergillus sydowii CBMAI 935, and the filamentous terrestrial fungi Aspergillus sp. FPZSP 146 and Aspergillus sp. FPZSP 152. A compound with an uncommon CN-bearing stereogenic center at the α-C position was obtained by enantioselective reactions mediated in the presence of the microorganisms yielding the (R)-2-cyano-3-(furan-2-yl) propanamide 3a. Its isolated yield and e.e. ranged from 86% to 98% and 39% to 99%, respectively. The absolute configuration of the biotransformation products was determined by time-dependent density functional theory (TD-DFT) calculations of electronic circular dichroism (ECD) spectra. Finally, the tautomerization of 2-cyano-3-(furan-2-yl) propanamide 3a to form an achiral ketenimine was observed and investigated in presence of protic solvents.