New methods for resolution of hydroxychloroquine by forming diastereomeric salt and adding chiral mobile phase agent on RP-HPLC.

Hydroxychloroquine (HCQ), 2-([4-([7-Chloro-4-quinolyl]amino)pentyl]ethylamino)ethanol, exhibited significant biological activity, while its side effects cannot be overlooked. The RP-HPLC enantio-separation was investigated for cost-effective and convenient optical purity analysis of HCQ. The thermodynamic resolution of Rac-HCQ, driven by enthalpy and entropy, was achieved on the C18 column using Carboxymethyl-ß-cyclodextrin (CM-ß-CD) as the chiral mobile phase agent (CMPA). The effects of CCM-ß-CD, pH, and triethylamine (TEA) V% on the enantio-separation process were explored. Under the optimum conditions at 24°C, the retention times for the two enantiomers were t R 1 = 29.39 min $$ {t}_{R1}=29.39\ \min $$ and t R 2 = 32.42 min $$ {t}_{R2}=32.42\ \min $$ , resulting in R s = 1.87 $$ {R}_s=1.87 $$ . The resolution via diastereomeric salt formation of Rac-HCQ was developed to obtain the active pharmaceutical ingredient of single enantiomer S-HCQ. Di-p-Anisoyl-L-Tartaric Acid (L-DATA) was proved effective as the resolution agent for Rac-HCQ. Surprisingly, it was found that refluxing time was a key fact affecting the resolution efficiency, which meant the kinetic dominate during the process of the resolution. Four factors-solvent volume, refluxing time, filtration temperature, and molar ratio-were optimized using the single-factor method and the response surface method. Two cubic models were established, and the reliability was subsequently verified. Under the optimal conditions, the less soluble salt of 2L-DATA:S-HCQ was obtained with a yield of 96.9% and optical purity of 63.0%. The optical purity of this less soluble salt increases to 99.0% with a yield of 74.2% after three rounds recrystallization.

Binary Mixtures of Meloxicam and L-Tartaric Acid for Oral Bioavailability Modulation of Pharmaceutical Dosage Forms.

Binary mixtures of active pharmaceutical ingredients (API) are researched to improve the oral bioavailability of pharmaceutical dosage forms. The purpose of this study was to obtain mixtures of meloxicam and L-tartaric acid because tartaric acid improves intestinal absorption and meloxicam is more soluble in a weakly basic environment. The mixtures in the 0-1 molar fraction range, obtained from solvent-assisted mechanosynthesis, were investigated by differential scanning calorimetry (DSC), Fourier Transform Infrared (FTIR) spectroscopy, Fourier Transform Raman spectroscopy (FT-Raman), X-ray powder diffraction (XRD) and solubility tests. The physicochemical characteristics of the compounds obtained from DSC data reveal, for the first time, the formation of a co-crystal at meloxicam molar fraction of 0.5. FTIR spectroscopy data show the existence of hydrogen bonds between the co-crystal components meloxicam and L-tartaric acid. FT-Raman spectroscopy was used complementary with FT-IR spectroscopy to analyze the pure APIs and their mixtures, to emphasize the appearance/disappearance and the shifts of the position/intensity of vibrational bands, following the formation of hydrogen-bonded structures or van der Waals interactions, and to especially monitor the crystal lattice vibrations below 400 cm-1. The experimental results obtained by X-ray powder diffraction confirmed the formation of the co-crystal by the loss and, respectively, the apparition of peaks from the single components in the co-crystal diffractogram. The solubility tests showed that the co-crystal product has a lower aqueous solubility due to the acidic character of the other component, tartaric acid. However, when the solubility tests were performed in buffer solution of pH 7.4, the solubility of meloxicam from the co-crystal mixture was increased by 57% compared to that of pure meloxicam. In conclusion, the studied API mixtures may be considered potential biomaterials for improved drug release molecular solids.

Deciphering the stereo-specific catalytic mechanisms of cis-epoxysuccinate hydrolases producing L(+)-tartaric acid.

Microbial epoxide hydrolases, cis-epoxysuccinate hydrolases (CESHs), have been utilized for commercial production of enantiomerically pure L(+)- and D(-)-tartaric acids for decades. However, the stereo-catalytic mechanism of CESH producing L(+)-tartaric acid (CESH[L]) remains unclear. Herein, the crystal structures of two CESH[L]s in ligand-free, product-complexed, and catalytic intermediate forms were determined. These structures revealed the unique specific binding mode for the mirror-symmetric substrate, an active catalytic triad consisting of Asp-His-Glu, and an arginine providing a proton to the oxirane oxygen to facilitate the epoxide ring-opening reaction, which has been pursued for decades. These results provide the structural basis for the rational engineering of these industrial biocatalysts.

Modulation of the oxidative damage, inflammation, and apoptosis-related genes by dicinnamoyl-L-tartaric acid in liver cancer.

Cancer cells can become resistant to existing treatments over time, so it is important to develop new treatments that target different pathways to stay ahead of this resistance. Many cancer treatments have severe side effects that can be debilitating and even life-threatening. Developing drugs that can effectively treat cancer while minimizing the risks of these side effects is essential for improving the quality of life of cancer patients. The study was designed to explore whether the combination of dicinnamoyl-L-tartaric (CLT) and sorafenib ((SOR), an anti-cancer drug)) could be used to treat hepatocellular carcinoma (HCC) in the animal model and to assess whether this combination would lead to changes in certain biomarkers associated with the tumour. In this study, 120 male mice were divided into 8 groups of 15 mice each. A number of biochemical parameters were measured, including liver functions, oxidative stress (malondialdehyde, (MDA); nitric oxide (NO)), and antioxidative activity (superoxide dismutase (SOD), and glutathione peroxidase (GPx)). Furthermore, the hepatic expressions of Bax, Beclin1, TNF-α, IL1ß, and BCl-2 genes were evaluated by qRT-PCR. The combination of SOR and CLT was found to reduce the levels of liver enzymes, such as AST, ALT, ALP, and GGT, and reduce the pathological changes caused by DAB and PB. The upregulation of TNF-α, IL1ß, and Bcl-2 genes suggests that the CLT was able to initiate an inflammatory response to combat the tumor, while the downregulation of the Bax and Beclin1 genes indicates that the CLT was able to reduce the risk of apoptosis in the liver. Furthermore, the combination therapy led to increased expression of cytokines, resulting in an enhanced anti-tumor effect.

L-Tartaric Acid Inhibits Diminazene-induced Vasorelaxation in Isolated Rat Aorta.

AIMS: The study investigated the effect of L-tartaric acid on diminazene-indiuced vasorelaxation. BACKGROUND: Diminazene is known to induce vasorelaxation through the stimulation of angiotensin-converting enzyme (ACE-2). OBJECTIVE: This work was designed to study the effect of L-tartaric acid on diminazene-induced vasorelaxation using an ex vivo approach. MATERIAL AND METHODS: In the current investigation, the inhibitory effect of L-tartaric acid on diminazene-induced relaxation. RESULTS: The results confirmed that L-tartaric acid was able to inhibit in a dose-dependent manner diminazene-induced vasorelaxation. CONCLUSION: This investigation provides important experimental evidence of the efficacy of L-tartaric acid in inhibiting diminazene-induced vasorelaxation.

L-Tartaric Acid Exhibits Antihypertensive and Vasorelaxant Effects: The Possible Role of eNOS/NO/cGMP Pathways.

AIMS: The aim of the study was to investigate the antihypertensive effect of L-Tartaric acid. BACKGROUND: L-Tartaric acid (L-TA) is a well-known weak organic acid that naturally occurs in a wide range of fruits, most notably in grapes, tamarind, and citrus. OBJECTIVE: The present study aimed to assess the effect of acute and subchronic administration of L-TA on blood pressure parameters in normotensive and hypertensive rats as well as its vasorelaxant potency. METHODS: In the current study, the antihypertensive activity of L-TA was pharmacologically studied. L-NAME-induced hypertensive and normotensive rats received L-TA (80 and 240 mg/kg) orally over six hours for the acute experiment and seven days for the subchronic treatment. Thereafter, systolic, diastolic, mean, mid arterial blood pressure, and pulse pressure as well as heart rate were evaluated. In the in vitro experiment, the vasorelaxant ability of L-TA was performed in ratisolated thoracic aorta. RESULTS: An important drop in blood pressure was recorded in L-NAME-induced hypertensives treated with L-TA. This molecule also produced a dose-dependent relaxation of the aorta precontracted with norepinephrine (NEP) and KCl. The study demonstrated that the vasorelaxant capacity of L-TA seems to be exerted through the activation of eNOS/NO/cGMP pathways.

Efficient Suzuki coupling over novel magnetic nanoparticle: Fe3O4/L-(+)-tartaric acid/Pd(0).

A new eco-friendly catalytic system is devised for C-C bond formation through Suzuki coupling, using an impressive nanocatalyst (Fe3O4/L-(+)-tartaric acid/Pd-NPs). It contains immobilized palladium (0) onto magnetite nanoparticles, stabilized by tartaric acid, and is characterized by FT-IR, XRD, EDS, SEM, TEM, TGA, and VSM. The catalyst is used in an efficient synthesis of biaryls in EtOH/H2O (1:1), in the presence of K2CO3. Our Fe3O4/tartaric acid/Pd-NPs exhibit magnetic recoverability and reusability for five cycles without measurable loss of its activity.

In vivo Antihyperglycemic and Antidyslipidemic Effects of L-Tartaric Acid.

AIMS: The aim of the study was to investigate the antihyperglycemic effect of L-Tartaric acid. BACKGROUND: L-Tartaric acid is a natural product with possible beneficial effects on health. OBJECTIVE: The goal of this work was to evaluate the antihyperglycemic and antidyslipidemic effects of L-Tartaric acid (L-TA) in rats. MATERIALS AND METHODS: In the first model, the effects of L-TA (10 and 40 mg/kg) on diabetes conditions induced by streptozotocin (STZ) in rats were investigated. In the second model, the effects of L-TA (40 and 80 mg/kg) on dyslipidemia induced by tyloxapol (Triton WR-1339) in rats were assessed. RESULTS: L-TA (40 mg/kg) had improved all studied parameters. L-TA at 40 mg/kg was able to significantly reduce glycaemia, improve oral glucose tolerance (OGT), increase glycogen content in liver and extensor digitorum longus (EDL) muscle, and ameliorate the lipidic profile and atherogenic indices in STZ-diabetic rats. CONCLUSION: L-Tartaric acid was able to exhibit antihyperglycemic and antidyslipidemic effects in STZ-induced diabetic rats. Moreover, the antidyslipidemic effect of L-Tartaric acid was confirmed in tyloxapol-induced hyperlipidemic rats.

Enhanced degradation mechanism of tetracycline by MnO2 with the presence of organic acids.

In this study, we constructed MnO2/organic acid (OA) systems using MnO2 colloid, the most reactive phase of Mn(IV), and two kinds of OA (oxalic acid and l-tartaric acid). We investigated the effect of OA on tetracycline (TC) degradation by MnO2. The results show that both OA obviously accelerate TC degradation by MnO2. Mn(III) formed during the reaction lead to the acceleration. Mn(III)-oxalate complex formed in oxalic acid system resulted in the lower degradation efficiency than that in l-tartaric acid system. The acceleration of oxalic acid was decreased when the concentration was more than 75 µM, and even completely disappeared with the concentration of 500 µM, owning to the fact that excess oxalic acid decreased the pH and some MnO2 was fast reduced to Mn2+ by oxalic acid and unable to react with TC. The impact of pH on TC degradation resulted from the influences of H+ on MnO2 redox potentials and TC deprotonation. And acidic conditions accelerated TC degradation. The addition of Mg2+, Ca2+, Fe3+ and Zn2+ exhibited an inhibitory effect in both systems for their occupying reactive sites on MnO2 surface and blocking the access of TC to MnO2. Similar intermediates in the two systems were detected, indicating a similar TC degradation mechanism including a series of reactions like dehydration, hydroxylation and oxidation. The MnO2/OA system provides an efficient treatment of TC in wastewater. And it is also noticeable that MnO2/OA system should also have an important effect on the fate of pollutants in environment, from our results.

[Determination of the enantiomers of salmeterol xinafoate in salmeterol fluticasone powder inhalant by chiral nonaqueous capillary electrophoresis].

Salmeterol xinafoate (SalX) is one of the ideal drugs used for the treatment of nocturnal asthma attacks and daily maintenance. The molecular structure of SalX contains a chiral carbon atom, and thus, SalX has two enantiomers, viz. (R)-SalX and (S)-SalX. It is clinically administered in the racemic form. Related studies have shown that the two enantiomers of SalX are quite different in pharmacology, toxicology, and other aspects. Therefore, it is of great significance to establish an analytical method for the chiral separation and determination of the SalX enantiomers to guarantee their quality and ensure their safety and effectiveness in clinical use. In this study, a chiral nonaqueous capillary electrophoresis (NACE) method, using a L(+)-tartaric acid-boric acid complex as the chiral selector, was established to determine the enantiomers of SalX in salmeterol fluticasone powder inhalant. The L(+)-tartaric acid-boric acid complex was synthesized in situ by the reaction of L(+)-tartaric acid and boric acid in methanol solution. The ion pair principle was considered the enantioseparation mechanism, and the non-aqueous system was found to be more favorable for ion pair formation, which is useful for chiral recognition. Chiral separation is based on the reversible formation of diastereomeric ion pairs between the negatively charged L(+)-tartaric acid-boric acid complex and the positively charged salmeterol enantiomers. Due to the difference in ion-pair binding ability between different enantiomers, the apparent electrophoretic mobilities of different enantiomers were also different, resulting in chiral separation in NACE. To achieve good resolution, the effects of L(+)-tartaric acid concentration, boric acid concentration, and apparent pH (pH* ) on the chiral separation were investigated. The optimized buffer solution (pH* 0.93) contained 120.0 mmol/L L(+)-tartaric acid and 120.0 mmol/L boric acid in methanol. Other experimental conditions were as follows: uncoated fused-silica capillary with an I. D. of 50.0 µm, a total length (Ltot) of 64.5 cm, and an effective length (Leff) of 55.5 cm, along with gravity injection of 17.5 cm×10.0 s, detection wavelength of 225 nm, room temperature, and operating voltage of 20.0 kV. Under these experimental conditions, the two enantiomers of SalX achieved a resolution of 2.18 within 18.0 min. Both enantiomers showed a good linear relationship of the peak area in the concentration range of 27.5-800.0 mg/L, the correlation coefficient (r) being greater than 0.9990. The detection limit (S/N=3) and quantitative limit (S/N=10) were 7.5 mg/L and 25.0 mg/L, respectively; the standard recovery was 98.1%-101.9%, with relative standard deviations (RSDs) of 1.2%-1.9%. The intra- and inter-day precisions were examined, and the RSDs of the peak area and migration time were found to be below 4.9% and 1.9%, respectively, indicating good repeatability (inter-day) and reproducibility (inter-day) of the method. The established chiral NACE method was used to determine the two SalX enantiomers in a random salmeterol fluticasone powder inhalant purchased from a local market. The results showed that the percentage of labeled quantities was 98.7% for both enantiomer 1 and enantiomer 2, with RSDs of 2.5% and 2.7%, respectively. Thus, this method is simple, feasible, accurate, and inexpensive, and can be applied for the determination of SalX enantiomers in commercially available salmeterol fluticasone powder inhalants.

Isolation of Penicillium expansum WH-3 for the production of L(+)-tartaric acid.

The L(+)-form of tartaric acid (L(+)-TA) exists extensively in nature, and is widely used in the food, chemical, textile, building, and pharmaceutical industries (Su et al., 2001). The main method for L(+)-TA production is microbial transformation by cis-epoxysuccinate hydrolase (CESH), which can catalyze the asymmetric hydrolysis of cis-epoxysuccinic acid or its salts to TA or tartrate (Bao et al., 2019). Seventeen species containing CESH have been isolated so far. However, most species for L(+)-TA production have been reported from bacteria (Xuan and Feng, 2019). The only fungus isolated from soil by our lab recently, that could be used as catalyst for the process under acidic condition, is Aspergillus niger WH-2 (Bao et al., 2020). In order to find strains with new characteristics, this study attempted to isolate a new CESH source from fungi and investigate its application value.

Isolation of a novel strain Aspergillus niger WH-2 for production of L(+)-tartaric acid under acidic condition.

OBJECTIVES: To isolate a novel cis-epoxysuccinate hydrolase (CESH)-producing fungus for production of L( +)-tartaric acid, before this, all strains were selected from bacteria. RESULTS: A CESH-producing fungus was first isolated from soil and identified as Aspergillus niger WH-2 based on its morphological properties and ITS sequence. The maximum activity of hyphaball and fermentation supernatants was 1278 ± 64 U/g and 5.6 ± 0.3 U/mL, respectively, in a 5 L fermenter based on the conditions optimized on the flask. Almost 70% of CESH was present in hyphaball, which maintained 40% residual activity at pH 4.0 and showed a good acid stability (pH 3.0-10.0), high conversion rate (> 98%), and enantioselectivity (EE > 99.6%). However, the reported CESHs from bacteria can't be catalyzed under acidic conditions. CONCLUSIONS: The Aspergillus niger WH-2 was the first reported CESH-producing fungus, which could biosynthesize L ( +)-tartaric acid under acidic conditions and provide an alternative catalyst and process.

Isolation of Penicillium expansum WH-3 for the production of L(+)-tartaric acid / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

The L(+)-form of tartaric acid (L(+)-TA) exists extensively in nature, and is widely used in the food, chemical, textile, building, and pharmaceutical industries (Su et al., 2001). The main method for L(+)-TA production is microbial transformation by cis-epoxysuccinate hydrolase (CESH), which can catalyze the asymmetric hydrolysis of cis-epoxysuccinic acid or its salts to TA or tartrate (Bao et al., 2019). Seventeen species containing CESH have been isolated so far. However, most species for L(+)-TA production have been reported from bacteria (Xuan and Feng, 2019). The only fungus isolated from soil by our lab recently, that could be used as catalyst for the process under acidic condition, is Aspergillus niger WH-2 (Bao et al., 2020). In order to find strains with new characteristics, this study attempted to isolate a new CESH source from fungi and investigate its application value.

In vitro effects of the asymmetric peptidomimetic 157, containing l-tartaric acid core and valine/leucine substituents, on Leishmania amazonensis promastigotes and amastigotes.

The current treatments for leishmaniasis bump into several obstacles, including low efficacy, high costs, long monitoring, and several/severe side effects. Consequently, the search for promising compounds is a tangible need. Recently, we reported the anti-Leishmania amazonensis action of asymmetric peptidomimetic compounds containing tartaric acid as core, especially the 157 derivative that contains valine/leucine substituents in its structure. Herein, we decipher the multiple effects of 157 on the L. amazonensis physiology and on the interaction process with macrophages. The peptidomimetic 157 induced significant changes on the morphometric (internal granularity reduction as judged by flow cytometer) and on the ultrastructural (round-shaped parasites, presence of plasma membrane blebs and flagellum loss as visualized by scanning electron microscopy) aspects of treated promastigotes compared to untreated ones. The alteration on the plasma membrane permeability was confirmed by the passive incorporation of propidium iodide in 157-treated promastigotes. In parallel, the low viability of promastigotes was also associated to the perturbation of mitochondrial transmembrane electric potential. These combined results demonstrated that 157 induced irreversible metabolic damages that led to L. amazonensis death. The pre-treatment of promastigotes with 157 inhibited the association index with macrophages in a typically dose-dependent manner. Additionally, 157 significantly reduced the number of intramacrophage amastigotes after 72 h of drug contact, presenting an IC50 value of 30.2 µM. Under our experimental conditions, 157 showed higher toxicity to promastigotes and amastigotes when compared to RAW cells, resulting in good selective indexes. Therefore, 157 can be considered as an interesting candidate for further optimization, since its synthesis is simple and cheap.

Analysis and Enantioseparation of Amino Acids by Liquid Chromatography.

Enantioseparation studies of proteinogenic, non-proteinogenic, and dansyl amino acids are described herein by using liquid chromatographic techniques, i.e., HPLC and TLC. A researcher who wants to perform amino acid (AA) analysis or separate enantiomers of AAs by HPLC or TLC can follow the method. Figures included represent the actual experiments.Synthesis and application of chiral derivatizing reagents (CDRs) based on cyanuric chloride (CC) and difluorodinitrobenzene (DFDNB) have been described for AA analysis and enantioseparation by indirect approach. The methods represent pre-column derivatization of AAs and represent a good and less expensive substitute of AA analyzer. The application of commercial "Chiralplate" and use of erythromycin and L-tartaric acid have been described as chiral selector either as impregnating reagent in the stationary phase or as an additive in the mobile phase for direct enantioseparation by TLC. Application of the homemade TLC plates has also been described; the methods are successful in obtaining the native enantiomer as well.

Indirect synchronous fluorescence spectroscopy and direct high-performance thin-layer chromatographic methods for enantioseperation of zopiclone and determination of chiral-switching eszopiclone: Evaluation of thermodynamic quantities of chromatographic separation.

Economic and enantioselective synchronous fluorescence spectroscopy and high-performance thin-layer chromatography methods have been developed and validated as per ICH guidelines for the separation of zopiclone enantiomers using L-(+)-tartaric acid as a chiral selector, followed by determination of the chiral-switching eszopiclone. Synchronous fluorescence spectroscopy was successfully applied for chiral recognition of R & S enantiomers of zopiclone at ∆λ = 110 nm based on creating of diastereomeric complexes with 0.06M tartaric acid in an aqueous medium containing 0.2M disodium hydrogen orthophosphate. Synchronous fluorescence intensities of eszopiclone were recorded at 296 nm in concentration range 0.2- to 4-µg/mL eszopiclone. High-performance thin-layer chromatography method depends on resolution of zopiclone enantiomers on achiral HPTLC silica-gel plates using acetonitrile:methanol:water (8:2:0.25, v/v/v) containing L-(+)-tartaric acid as a chiral mobile-phase additive followed by densitometric measurements at 304 nm in concentration range of 1 to 10 µg/band of eszopiclone. The effect of chiral-selector concentration, pH, and temperature on the resolution have been studied and optimized for the proposed methods. The cited procedures were successfully applied to determine eszopiclone in commercial tablets of pure and racemic forms. Enantiomeric excess was evaluated using optical purity test and integrated peak area to describe the enantiomeric ratio. Thermodynamics of chromatographic separation, enthalpy, and entropy were evaluated using the Van't Hoff equation. The proposed methods were found to be selective for identification and determination of the eutomer in drug substances and products.

A novel method for classification of wine based on organic acids.

Bio-electronic tongue was linked to artificial intelligence processing unit and used for classification of wines based on carboxylic acids levels, which were indirectly related to malolactic fermentation. The system employed amperometric biosensors with lactate oxidase, sarcosine oxidase, and fumarase/sarcosine oxidase in the three sensing channels. The results were processed using two statistical methods - principal component analysis (PCA) and self-organized maps (SOM) in order to classify 31 wine samples from the South Moravia region in the Czech Republic. Reference assays were carried out using the capillary electrophoresis (CE). The PCA patterns for both CE and biosensor data provided good correspondence in the clusters of samples. The SOM treatment provided a better resolution of the generated patterns of samples compared to PCA, the SOM derived clusters corresponded with the PCA classification only partially. The biosensor/SOM combination offers a novel procedure of wine classification.

Effect of acid deamidation-alcalase hydrolysis induced modification on functional and bitter-masking properties of wheat gluten hydrolysates.

The low solubility of wheat gluten (WG) considerably limits its application. Owing to its high hydrolytic efficiency, alcalase was the protease selected for the enzymatic hydrolysis of WG. The functional properties of WG hydrolysate prepared by alcalase (AHWG) with a hydrolysis degree (DH) of 10% were better than those with DH 5% and DH 15%. The application of AHWG was hindered by its bitterness. To mask the bitterness of AHWG, WG was respectively deamidated with acetic acid, tartaric acid, and citric acid, followed by being hydrolyzed by alcalase to DH 10%. The citric acid deamidation-alcalase hydrolysis WG hydrolysate (CDAH) exhibited the best functional properties. Partial least squares regression analysis results indicated that CDAH exhibited an enhanced bitter-masking property attributable to a high content of umami taste amino acids (glutamic acid and aspartic acid). Thus, CDAH showed the greatest potential as a modified WG product to expand the application of WG.

Asymmetric peptidomimetics containing L-tartaric acid core inhibit the aspartyl peptidase activity and growth of Leishmania amazonensis promastigotes.

Aspartyl-type peptidases are promising chemotherapeutic targets in protozoan parasites. In the present work, we identified an aspartyl peptidase activity from the soluble extract of Leishmania amazonensis promastigotes, which cleaved the fluorogenic peptide 7-methoxycoumarin-4-acetyl-Gly-Lys-Pro-Ile-Leu-Phe-Phe-Arg-Leu-Lys(DNP)-D-Arg-amide (cathepsin D substrate) under acidic pH conditions at 37°C, showing a KM of 0.58 µM and Vmax of 129.87 fluorescence arbitrary units/s mg protein. The leishmanial aspartyl peptidase activity was blocked by pepstatin A (IC50 = 6.8 µM) and diazo-acetyl-norleucinemetilester (IC50 = 10.2 µM), two classical aspartyl peptidase inhibitors. Subsequently, the effects of 6 asymmetric peptidomimetics, containing L-tartaric acid core, were tested on both aspartyl peptidase and growth of L. amazonensis promastigotes. The peptidomimetics named 88, 154 and 158 promoted a reduction of 50% on the leishmanial aspartyl peptidase activity at concentrations ranging from 40 to 85 µM, whereas the peptidomimetic 157 was by far the most effective, presenting IC50 of 0.04 µM. Furthermore, the peptidomimetics 157 and 154 reduced the parasite proliferation in a dose-dependent manner, displaying IC50 values of 33.7 and 44.5 µM, respectively. Collectively, the peptidomimetic 157 was the most efficient compound able to arrest both aspartyl peptidase activity and leishmanial proliferation, which raises excellent perspectives regarding its use against this human pathogenic protozoan.

Impact of fluorescent lighting on the browning potential of model wine solutions containing organic acids and iron.

Model wine solutions containing organic acids, individually or combined, and iron(III), were exposed to light from fluorescent lamps or stored in darkness for four hours. (-)-Epicatechin was then added, and the solutions incubated in darkness for 10days. Browning was monitored by UV-visible absorption spectrophotometry and UHPLC-DAD. The pre-irradiated solutions containing tartaric acid exhibited increased yellow/brown coloration compared to the dark controls mainly due to reaction of the tartaric acid photodegradation product glyoxylic acid with (-)-epicatechin to form xanthylium cation pigments. In these solutions, browning decreased as the concentrations of organic acids other than tartaric acid increased. Xanthylium cations were also detected in the pre-irradiated malic acid solution. However, in the malic acid, succinic acid, citric acid and lactic acid solutions, any coloration was mainly due to the production of dehydrodiepicatechin A, which was largely independent of prior light exposure, but strongly affected by the organic acid present.