Thermogravimetric analysis of soot combustion in the presence of ash and soluble organic fraction

Soot (Printex U, PU) combustion in the presence of ash and soluble organic fraction (SOF) was studied by thermogravimetric analysis (TGA). The comprehensive combustion index, combustion stability index and peak temperature were collected to evaluate the combustion performance of soot/ash/SOF mixtures. Compared with SiO₂, Fe₂O₃ and CaSO₄ nanoparticles, ZnO nanoparticles efficiently accelerate soot combustion with excellent oxygen carrying abilities. When the weight ratio of the PU/ZnO mixture is 1 : 1, this acceleration effect is maximized in the soot combustion process. The comprehensive combustion and combustion stability indices increase from 0.667 × 10⁻⁷%² min⁻² °C⁻³ and 23.53 × 10⁵ to 1.296 × 10⁻⁷%² min⁻² °C⁻³ and 39.53 × 10⁵, compared to pure PU, respectively. Compared with the PU/ZnO mixture, the soot combustion had inferior results after adding two oils as the simulative SOF. The 15W lubricant had the minimum negative impact compared to 0# diesel fuel. The comprehensive combustion and combustion stability indices reach the maximum values of 1.074 × 10⁻⁷%² min⁻² °C⁻³ and 33.29 × 10⁵ at the 1 : 1 : 0.1 weight ratio of PU/ZnO/15W, which grew by 62% and 42% compared to pure PU, respectively. This work contributes to an understanding of the combined effect of ash and SOF on soot combustion.

Soot (Printex U, PU) combustion in the presence of ash and soluble organic fraction (SOF) was studied by thermogravimetric analysis (TGA).     

Development and validation of a sensitive LC-MS/MS method for pioglitazone: application towards pharmacokinetic and tissue distribution study in rats

In the present study, a sensitive LC-MS/MS method was developed and validated to measure pioglitazone (PGZ) concentrations in rat plasma and tissues. The chromatographic separation was achieved by using a YMC Pro C₁₈ column (100 mm × 4.6 mm, 3μ) with a mobile phase consisting of formic acid (0.1% v/v) and acetonitrile (5 : 95) at a flow rate of 0.7 mL min⁻¹ and injection volume of 10 μL (IS: rosiglitazone). Mass spectrometric detection was done using triple quadrupole mass spectrometry using the ESI interface operating in a positive ionization mode. The developed method was validated over a linearity range of 1–500 ng mL⁻¹ with detection and a lower quantification limit of 0.5 ng mL⁻¹ and 1 ng mL⁻¹. The method accuracy ranged from 95.89–98.78% (inter-day) & 93.39–97.68% (intra-day) with a precision range of 6.09–8.12% for inter-day & 7.55–9.87% for intra-day, respectively. The PGZ shows the highest C_max of 495.03 ng mL⁻¹ in plasma and the lowest C_max, 24.50 ± 2.71 ng mL⁻¹ in bone. The maximum T_max of 5.00 ± 0.49 h was observed in bone and a minimum of 1.01 ± 0.05 h in plasma. The AUC_{(0–24 h and 0–∞)} values are highest in plasma (1056.58 ± 65.78 & 1069.38 ± 77.50 ng h⁻¹ mL⁻¹) and lowest in brain (166.93 ± 15.70 &167.12 ± 16.77 ng h⁻¹ mL⁻¹), and the T_1/2 was highest in plasma (5.62 ± 0.74 h) and lowest in kidney (2.78 ± 0.19). The developed method was successfully used to measure the PGZ pharmacokinetic and tissue distribution. Further, the developed method could be utilized for validating target organ (adipose tissue) specific delivery of PGZ (nano-formulations) in addition to conventional dosage forms.

The developed method was investigated for target and off-target distribution of pioglitazone and could be applied to validate the site-specific delivery systems.     

Spermidine enhanced resistance of Chlorella to high levels of CO2 and light intensity for improving photosynthetic growth rate

In order to promote the photosynthetic growth rate of Chlorella in the presence of flue gas CO₂ from coal-fired power plants, spermidine was first used to enhance cellular resistance to a high CO₂ concentration (15%) and high light intensity (30 000 lux). It was found that low concentrations (100–300 μM) of spermidine significantly enhanced the photosynthetic growth rate of Chlorella. The accelerated cell division decreased the cell diameter from 3.64 μm to 2.71 μm and the fractal dimension from 1.60 to 1.49, and the activity of total superoxide dismutase (T-SOD) increased from 0.48 U mL⁻¹ to 5.33 U mL⁻¹. Expression levels of key enzymes of photosystems I and II, ATP synthase and transportase markedly increased, thereby enhancing the electron transport and energy supply that reduced oxidative damage. Finally, an enhanced cellular resistance to the high CO₂ concentration and high light intensity increased the biomass yield from 0.11 g L⁻¹ to 1.71 g L⁻¹ (300 μM).

Spermidine enhanced resistance of Chlorella to high levels of CO₂ and light intensity.     

Development of a colorless Centella asiatica (L.) Urb. extract using a natural deep eutectic solvent (NADES) and microwave-assisted extraction (MAE) optimized by response surface methodology

This study outlines a green process for Centella asiatica (L.) Urb. (CA) extraction. Natural deep eutectic solvents (NADESs) and microwave-assisted extraction (MAE) were combined to provide a high bioactive compound yield and high antioxidant activity. Among the NADESs evaluated, the combination of acetylcholine chloride : malic acid : water (1 : 2 : 2): water (40 : 60) was the best for extraction. These conditions provide high madecassoside (MS) (21.7 mg g⁻¹ dry weight) and asiaticoside (AS) (12.7 mg g⁻¹ dry weight) yields, with greater than 80% (v/v) EtOH (13.3 mg g⁻¹ MS and 7.80 mg g⁻¹ AS). In addition, the extracts from this process showed higher antioxidant activity (IC₅₀ = 0.26 mg mL⁻¹) than the CA aqueous EtOH and water extracts. Moreover, the color of the extract products was less green than that of the extracts prepared using EtOH and aqueous EtOH as solvents, which are suitable for cosmeceutical products. Response surface methodology (RSM) was used for MAE optimization. The ANOVA data from the central composition design (CCD) of RSM were fitted with quadratic models yielding acceptable R² (>0.93), adjusted R² (>0.87), predicted R² (>0.81), and nonsignificant lack of fit (p  > 0.05) values. The quadratic model was validated using optimal conditions (30 s, power 300 W, and a liquid to solid ratio 20 mL g⁻¹), and the model validation showed more than 80% accuracy in both MS and AS yields. This research presented an effective green process for CA extraction, which resulted in an environmentally friendly CA extract requiring little energy consumption and no organic solvents.

This study outlines a green process for Centella asiatica (L.) Urb. (CA) extraction.     

Mesoporous-rich calcium and potassium-activated carbons prepared from degreased spent coffee grounds for efficient removal of MnO42− in aqueous media

Commercial ACs typically possess high surface areas and high microporosity. However, ACs with appreciable mesoporosity are growing in consideration and demand because they are beneficial for the adsorption of large species, such as heavy metal ions. Thus, in this study, degreased coffee grounds (DCG) were used as precursors for the production of ACs by means of chemical activation at 600 °C for the efficient removal of manganese in the form of MnO₄²⁻. One of the most common activating agents, ZnCl₂, is replaced by benign and sustainable CaCl₂ and K₂CO₃. Three ratios 1 : 1, 1 : 0.5 and 1 : 0.1 of precursor-to-activating agent (g g⁻¹) were investigated. Porosimetry indicates 1 : 1 CaCl₂ DCGAC is highly mesoporous (mesopore volume 0.469 cm³ g⁻¹). CaCl₂ DCGAC and K₂CO₃ DCGAC shows high adsorption capacities of 0.494 g g⁻¹ and 0.423 g g⁻¹, respectively for the uptake of MnO₄²⁻ in aqueous media. The adsorption process follows pseudo-second order kinetics inline with the Freundlich isotherm (R² > 0.9). Thermodynamic data revealed negative values of ΔG (approx −0.1751 kJ mol⁻¹) demonstrating that the adsorption process on 1 : 1 CaCl₂DCGAC was spontaneous.

Spent coffee grounds are an interesting high volume renewable resource for valorisation. Activation with CaCl₂ produces mesoporous carbons with high capacity for removal of MnO₄²⁻.     

Synthesis and anion recognition studies of new oligomethylene bis(nitrophenylureylbenzamide) receptors

A new series of oligomethylene bis(nitrophenylureylbenzamide) receptors were synthesized varying the relative position of the urea and amide groups (ortho4 and meta8) and the length of the oligomethylene chain (C₂ to C₈). An anion recognition study was performed with TBAX salts (X = AcO⁻, BzO⁻, F⁻, H₂PO₄⁻, and HP₂O₇³⁻) by UV-vis and ¹H NMR. The flexibility of these receptors allows a cooperative effect of both ureylbenzamide units in the receptors. Noteworthy, the ortho position favored the 1 : 1 stoichiometry in the complexes with the carboxylates. The formation of 2 : 1 receptor–anion complexes with both types of receptors 4 and 8 and with hydrogen pyrophosphate and high log K values obtained were very significant in this work. The NMR studies evidenced the formation of supramolecular complexes, even in a competitive solvent, such as DMSO.

Synthesis and supramolecular interaction of new oligomethylene bis(4-nitrophenylureylbenzamide) receptors with different anions.     

Content determination of ampicillin by Ni(ii)-mediated UV-Vis spectrophotometry

Ampicillin could be degraded under alkaline conditions, of which the degradation products formed a complex with Ni²⁺ in a ratio of 2 : 1 in ammonium hydroxide. According to the study, it was found that there was a characteristic absorption peak at the wavelength of 269 nm, and the molar absorption coefficient and the stability constant of the complex was 4.28 × 10³ L mol⁻¹ cm⁻¹ and 5.95 × 10⁹, respectively. The linear relationship between the concentration and absorbance was favorable at the range of 17.47–69.88 μg mL⁻¹. The regression equation was calculated as A = 0.0124C + 0.0053. The R² was 0.9990 and the detection limit was 0.52 μg mL⁻¹. Thus, the Ni²⁺ complex-based ultraviolet spectrophotometry has been created as a new method for indirect determination of ampicillin, with recovery rates from 98.68 to 102.7%, and the relative standard deviation (RSD) is from 0.7% to 1.7%, when applied for determining the content of practical samples.

Ampicillin could be degraded under alkaline conditions, of which the degradation products formed a complex with Ni²⁺ in a ratio of 2 : 1 in ammonium hydroxide.     

A fluorescence immunoassay based on CdTe : Zn/ZnS quantum dots for the rapid detection of bacteria,taking Delftia tsuruhatensis CM’13 as an example

A fluorescence immunoassay has been widely applied in different fields due to its high sensitivity, simple operations, and high accuracy. Quantum dots (QDs) are often selected as labels in a fluorescence immunoassay due to their high fluorescence, better stability, and biocompatibility. In this study, novel doped CdTe : Zn/ZnS QDs with stability and a high photoluminescence quantum yield (40.78%) were prepared by the water synthesis method and used as labels to conjugate with goat anti-rabbit IgG to establish a fluorescence immunoassay (FLISA) for bacteria compared to the traditional enzyme-linked immunosorbent assay (ELISA) based on the reaction between an antibody and an antigen. A good linear relationship between the fluorescence intensity and concentrations of D. tsuruhatensis CM13 was found when the concentrations were in the range of 10³ CFU mL⁻¹–10⁸ CFU mL⁻¹. The limit of detection (LOD) of D. tsuruhatensis CM13 was 1.25 × 10³ CFU mL⁻¹ by FLISA, which was about 80 times lower than the LOD obtained from ELISA (10⁵ CFU mL⁻¹). This indicated that our FLISA method has higher sensitivity than traditional ELISA, and the CdTe : Zn/ZnS QDs synthesized in this paper have good applications in the rapid sensitive detection of microorganisms.

A fluorescence immunoassay has been widely applied in different fields due to its high sensitivity, simple operations, and high accuracy.     

Effect of Bi2O3 content on the microstructure and electrical properties of SrBi2Nb2O9 piezoelectric ceramics

Lead-free ceramics, SrBi₂Nb₂O₉–xBi₂O₃ (SBN–xBi), with different Bi contents of which the molar ratio, n(Sr) : n(Bi) : n(Nb), is 1 : 2(1 + x/2) : 2 (x = −0.05, 0.0, 0.05, 0.10), were prepared by conventional solid-state reaction method. The effect of excess bismuth on the crystal structure, microstructure and electrical properties of the ceramics were investigated. A layered perovskite structure without any detectable secondary phase and plate-like morphologies of the grains were clearly observed in all samples. The value of the activation energy suggested that the defects in samples could be related to oxygen vacancies. Excellent electrical properties (e.g., d₃₃ = 18 pC N⁻¹, 2P_r = 17.8 μC cm⁻², ρ_rd = 96.4% and T_c = 420 °C) were simultaneously obtained in the ceramic where x = 0.05. Thermal annealing studies indicated the SBN–xBi ceramics system possessed stable piezoelectric properties, demonstrating that the samples could be promising candidates for high-temperature applications.

Lead-free ceramics, SrBi₂Nb₂O₉–xBi₂O₃ (SBN–xBi), with different Bi contents of which the molar ratio, n(Sr) : n(Bi) : n(Nb), is 1 : 2(1 + x/2) : 2 (x = −0.05, 0.0, 0.05, 0.10), were prepared by conventional solid-state reaction method.     

Synthesis and antibacterial and antiviral activities of myricetin derivatives containing a 1,2,4-triazole Schiff base

A series of novel myricetin derivatives containing a 1,2,4-triazole Schiff base were designed and synthesized. Their structures were systematically characterized using ¹H NMR, ¹³C NMR, and HRMS. During antibacterial bioassays, 6f, 6i, and 6q demonstrated a good inhibitory effect against Xanthomonas axonopodis pv. citri (Xac), with half-maximal effective concentration (EC₅₀) values of 10.0, 9.4, and 8.8 μg mL⁻¹, respectively, which were better than those of bismerthiazol (54.9 μg mL⁻¹) and thiodiazole copper (61.1 μg mL⁻¹). Note that 6w demonstrated a good inhibitory effect against Ralstonia solanacearum (Rs) with and EC₅₀ value of 15.5 μg mL⁻¹, which was better than those of bismerthiazol (55.2 μg mL⁻¹) and thiodiazole copper (127.9 μg mL⁻¹). Similarly, 6a, 6d, and 6e demonstrated a good inhibitory effect against Xanthomonas oryzae pv. oryzae (Xoo) with EC₅₀ values of 47.1, 61.2, and 61.0 μg mL⁻¹, respectively, which were better than those of bismerthiazol (148.2 μg mL⁻¹) and thiodiazole copper (175.5 μg mL⁻¹). Furthermore, we used scanning electron microscopy (SEM) to study the possible sterilization process of the target compound 6q against Xac. The results indicated the possibility of destroying the bacterial cell membrane structure, resulting in an incomplete bacterial structure, and thus achieving inhibition. Furthermore, antiviral bioassays revealed that most compounds exhibited excellent antiviral activity against tobacco mosaic virus (TMV) at a concentration of 500 μg mL⁻¹. The results of the molecular docking studies for 6g with TMV-CP (PDB code: 1EI7) showed that compound 6g had partially interacted with TMV-CP. Therefore, mechanistic studies of the action of compound 6g could be further studied based on that.

The myricetin derivatives containing a 1,2,4-triazole Schiff base were designed and synthesized. Antibacterial mechanism was investigated through SEM.     

Facile synthesis of highly conductive PEDOT:PSS via surfactant templates

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) nanoparticles in powder form with high electrical conductivity were synthesized via chemical oxidative polymerization. In addition, the effects of EDOT : PSS weight ratio, EDOT : Na₂S₂O₈ mole ratio, and surfactant concentration and type, namely hexadecyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS), and polyoxyethylene octyl phenyl ether (Triton X-100) on the properties of PEDOT:PSS were investigated. For the effect of EDOT : PSS weight ratio, at the EDOT : Na₂S₂O₈ mole ratio of 1 : 1, the EDOT : PSS weight ratio of 1 : 11 was the optimal condition to obtain electrical conductivity of 999.74 ± 10.86 S cm⁻¹ due to the high amount of PSS⁻ and SO₄²⁻ available to interact with the PEDOT chain with a low % PSSNa. For the effect of EDOT : Na₂S₂O₈ mole ratio, at the EDOT : PSS weight ratio of 1 : 11, the EDOT : Na₂S₂O₈ mole ratio of 1 : 2 was the best condition as it provided the highest dopant (PSS⁻ and SO₄²⁻) amount, while the % PSSNa was relatively low. For the effect of surfactant type and concentration, at the EDOT : PSS weight ratio of 1 : 11 and EDOT : Na₂S₂O₈ mole ratio of 1 : 2, Triton X-100 at 2.5CMC provided electrical conductivity higher than with CTAB and SDS. The thermal stability of PEDOT:PSS obtained from various conditions was investigated, and PEDOT:PSS without surfactant showed the highest thermal stability since it produced the highest char yield. In this study, the highest electrical conductivity of PEDOT:PSS, which was obtained in the presence of Triton X-100 to reduce the PSSNa amount, was 1879.49 ± 13.87 S cm⁻¹, the highest value reported to date.

The electrical conductivity of 1879.49 ± 13.87 S cm⁻¹ was achieved for PEDOT:PSS, which is the highest value reported to date.     

Development of a selective and sensitive colour reagent for gold and silver ions and its application to desktop scanner analysis

Desktop scanners can be favorable alternatives to sophisticated spectrophotometers for the assessment of analytes in complex real samples. Distinctively, our method has been thoroughly investigated, optimized, validated and successfully applied to the assessment of silver and gold in complex real samples, applying syringal rhodanine (SR) as a novel specifically tailored chromogenic reagent and using a desktop scanner as a versatile sensor. Maximum colour absorbance was obtained in the presence of cetylpyridinium chloride (CPC) and cetyltrimethylammonium chloride (CTAC) for silver and gold chelates, respectively. For each metal ion, two ternary complexes were formed depending on the SR concentration with stoichiometries of 1 : 1 : 1 and 1 : 2 : 3 (Ag–SR–CPC) and 1 : 2 : 3 and 1 : 3 : 4 (Au–SR–CTAC), respectively. The methods adhered to Beer''s law for 0.15–2.5 and 0.15–2.25 μg mL⁻¹ with detection limits of 0.0089 and 0.0163 μg mL⁻¹ for silver and gold, respectively. The molar absorptivities were 3.63 × 10⁴ and 6.15 × 10⁴ L mol⁻¹ cm⁻¹ at 550 nm and 554 nm, with Sandell''s sensitivity indexes of 0.0029 and 0.0032 μg cm⁻², respectively. The method was successfully applied to the assessment of silver and gold in a wide range of complex environmental samples.

Desktop scanners can be favorable alternatives to sophisticated spectrophotometers for the assessment of analytes in complex real samples.     

Fabrication of ZIF-71/Fe3O4/polythionine nanoarray-functionalized carbon cotton cloth for simultaneous extraction and quantitation of febuxostat and diclofenac

A sustainable hybrid material based on carbonized cotton cloth/zeolite imidazolate framework-71/Fe₃O₄/polythionine (CC/ZIF-71/Fe₃O₄/PTh) was synthesized and applied in ultrasound-assisted dispersive magnetic solid-phase extraction (USA-DMSPE) followed with high performance liquid chromatography-ultraviolet detection (HPLC-UV) for simultaneous quantitation of diclofenac (DIC) and febuxostat (FEB) in human plasma. The surface of CC was modified with nanoarrays of zeolite imidazolate framework-71/Fe₃O₄/Polythionine. At first, an in situ synthesis of ZIF-71 in the presence of CC was carried out, and followed with magnetization process and oxidative polymerization of thionine. The nano-modifier agents improved the merits of the sorbent involving stability, porosity, mast transfer, π–π interactions and selectivity of CC. Characterizations of the hybrid sorbent were examined with different instrumental techniques. The limits of detection (LODs, S/N = 3) were recognized 2.1 ng mL⁻¹ for DIC and 3.7 ng mL⁻¹ for FEB. Acceptable linearity (0.992 ≤ r² ≤0.996) and relatively broad dynamic ranges of 10.0–1800.0 ng mL⁻¹ and 15.0–2500.0 ng mL⁻¹ were achieved for DIC and FEB, respectively. Reasonable intra-assay (≤7.2%, n = 9) and inter-assay (≤7.5%, n = 9) precisions as well as appropriate accuracies (≤8.0%) were provided illustrating applicability of the current approach for analytical purposes. Eventually, CC/ZIF-71/Fe₃O₄/PTh was employed as four-part sorbent for the assessment of DIC and FEB in human plasma at trace levels and subsequently main pharmacokinetic data such as T_1/2, T_max,C_max, and AUC_0–24 of these drugs were comprehensively investigated.

Synthesis of a material based on carbonized cotton cloth/zeolite imidazolate framework was applied to ultrasound-assisted dispersive magnetic solid-phase extraction and high-performance liquid chromatography-ultraviolet to detect diclofenac and febuxostat in human plasma.     

A green synthesis and antibacterial activity of ferrocene-based thiazole derivatives in choline chloride/glycerol eutectic solvent

In this work, a green Hantzsch synthesis of 4-ferrocenylthiazole derivatives has been accomplished successfully. The Hantzsch reaction between bromoacetylferrocene and various aryl thioureas, 1-alkylindole-3- or 9-alkylcarbazole-3-carbothioamides proceeded efficiently in a deep eutectic solvent (DES) that is, choline chloride/glycerol (ChCl/Gly) (1 : 2 molar ratio) at 80 °C, avoiding the use of common volatile organic solvents. Moreover, the DES media could be reused up to three times without any appreciable decrease in the yield. The synthetic strategy has the attractive features such as mild and environmentally benign reaction conditions, experimental simplicity, easy work-up procedure and good yields. Subsequently, a preliminary screening for in vitro antibacterial activities of all these newly-synthesized compounds revealed that the halo-substituted (F, Cl, Br) compounds 3f–h showed significant antibacterial activities against Gram (+) bacterial B. subtilis and Gram (−) E. coli, among which the fluoro-substituted 3f possessed the best activity with the MIC value of 7.8125 μg mL⁻¹, being higher than the reference drug ciprofoxacin (15.625 μg mL⁻¹).

A green and effective Hantzsch thiazole synthesis of structurally intriguing ferrocene-based derivatives employing the eutectic mixture choline chloride/glycerol (1 : 2 molar ratio) as a sustainable solvent is described.     

Biological activity evaluation and action mechanism of chalcone derivatives containing thiophene sulfonate

A series of novel chalcone derivatives containing a thiophene sulfonate group were designed and synthesized. The structures of all title compounds were determined by ¹H-NMR, ¹³C-NMR and HRMS. Antibacterial bioassays indicated that, compound 2l demonstrated excellent antibacterial activities against Xanthomonas axonopodis pv. citri (Xac), with an EC₅₀ value of 11.4 μg mL⁻¹, which is significantly superior to those of bismerthiazol (BT) (51.6 μg mL⁻¹) and thiodiazole-copper (TC) (94.7 μg mL⁻¹). Meanwhile, the mechanism of action of compound 2l was confirmed by using scanning electron microscopy (SEM). In addition, compound 2e showed remarkable inactivation activity against Tobacco mosaic virus (TMV), with an EC₅₀ value of 44.3 μg mL⁻¹, which was superior to that of ningnanmycin (120.6 μg mL⁻¹). Microscale thermophoresis (MST) also showed that the binding of compounds 2e and 2h to Tobacco mosaic virus coat protein (TMV-CP) yielded K_d values of 0.270 and 0.301 μmol L⁻¹, which are better than that of ningnanmycin (0.596 μmol L⁻¹). At the same time, molecular docking studies for 2e and 2h with TMV-CP (PDB code: 1EI7) showed that the compound was embedded well in the pocket between the two subunits of TMV-CP in each case. These results suggested that chalcone derivatives containing a thiophene sulfonate group may be considered as activators in the design of antibacterial and antiviral agents.

Synthesis, antibacterial, antiviral activities and action mechanism of chalcone derivatives containing thiophene sulfonate.     

Discovery of quinolone derivatives as antimycobacterial agents

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), is an important public health issue. Current first-line drugs administered to TB patients have been in use for over 40 years, whereas second-line drugs display strong side effects and poor compliance. Additionally, designing effective regimens to treat patients infected with multi- and extremely-drug-resistant (MDR and XDR) strains of TB is challenging. In this report, we screened our compound library and identified compound 1 with antituberculosis activity and a minimal inhibitory concentration (MIC) against M. tuberculosis of 20 μg mL⁻¹. Structure optimization and the structure–activity relationship of 1 as the lead compound enabled the design and synthesis of a series of quinolone derivatives, 6a1–6a2, 6b1–6b36, 6c1, 6d1–6d14, 7a1–7a2, 7b1–7b2, 7c1, 8a1–8a5, 9a1–9a4 and 10a1–10a6. These compounds were evaluated in vitro for anti-tubercular activity against the M. tuberculosis H₃₇Rv strain. Among them, compounds 6b6, 6b12 and 6b21 exhibited MIC values in the range of 1.2–3 μg mL⁻¹ and showed excellent activity against the tested MDR-TB strain (MIC: 3, 2.9 and 0.9 μg mL⁻¹, respectively). All three compounds were non-toxic toward A549 and Vero cells (>100 and >50 μg mL⁻¹, respectively). In addition, an antibacterial spectrum test carried out using compound 6b21 showed that this compound specifically inhibits M. tuberculosis. These can serve as a new starting point for the development of anti-TB agents with therapeutic potential.

6b21: MIC against M. tb H₃₇Rv = 1.2 μg mL⁻¹, MIC against drug-resistant strains = 0.9 μg mL⁻¹, solubility = 132 μg mL⁻¹, non-cytotoxicity.     

Single crystal growth and structure analysis of type-I (Na/Sr)–(Ga/Si) quaternary clathrates

Single crystals of (Na/Sr)–(Ga/Si) quaternary type-I clathrates, Na_8−ySr_yGa_xSi_46−x, were synthesized by evaporating Na from a mixture of Na–Sr–Ga–Si–Sn in a 6 : 0.5 : 1 : 2 : 1 molar ratio at 773 K for 12 h in an Ar atmosphere. Electron-probe microanalysis and single-crystal X-ray diffraction revealed that three crystals from the same product were Na_8−ySr_yGa_xSi_46−x with x and y values of 7.6, 2.96; 8.4, 3.80; and 9.1, 4.08. It was also shown that increasing the Sr and Ga contents increased the electrical resistivity of the crystal from 0.34 to 1.05 mΩ cm at 300 K.

Single crystals of (Na/Sr)–(Ga/Si) quaternary type-I clathrates, Na_8−ySr_yGa_xSi_46−x, were synthesized by evaporating Na from a mixture of Na–Sr–Ga–Si–Sn in a 6 : 0.5 : 1 : 2 : 1 molar ratio at 773 K for 12 h in an Ar atmosphere.     

Binuclear and tetranuclear Zn(ii) complexes with thiosemicarbazones: synthesis,X-ray crystal structures,ATP-sensing,DNA-binding,phosphatase activity and theoretical calculations

Two Zinc(ii) complexes [Zn₄(L¹)₄]·2H₂O (1) and [Zn₂(L²)₂]·2H₂O (2) of pyruvaldehydethiosemicarbazone ligands are reported. The complexes were characterized by elemental analysis, IR, NMR, UV-vis spectroscopy and by single-crystal X-ray crystallography. X-ray crystal structure determinations of the complexes show that though Zn : ligand stoichiometry is 1 : 1 in both the complexes, the molecular unit is tetranuclear for 1 and binuclear for 2. Both the complexes show selective sensing of ATP at pH 7.4 (0.01 M HEPES) in CH₃CN–H₂O (9 : 1) medium in the presence of other anions like AcO⁻, NO₃⁻, F⁻, Cl⁻, H₂PO₄⁻, HPO₄²⁻ and P₂O₇²⁻. The UV-titration experiments of complexes 1 and 2 with ATP results in binding constants of 2.0(±0.07) × 10⁴ M⁻¹ and 7.1(±0.05) × 10³ M⁻¹ respectively. The calculated detection limits of 6.7 μM and 1.7 μM for 1 and 2 respectively suggest that the complexes are sensitive detectors of ATP. High selectivity of the complexes is confirmed by the addition of ATP in presence of an excess of other anions. DFT studies confirm that the ATP complexes are more favorable than those with the other inorganic phosphate anions, in agreement with the experimental results. Phosphatase like activity of both complexes is investigated spectrophotometrically using 4-nitrophenylphosphate (NPP) as a substrate, indicating the complexes possess significant phosphate ester hydrolytic efficiency. The kinetics for the hydrolysis of the substrate NPP was studied by the initial rate method at 25 °C. Michaelis–Menten derived kinetic parameters indicate that rate of hydrolysis of the P–O bond by complex 1 is much greater than that of complex 2, the k_cat values being 212(±5) and 38(±2) h⁻¹ respectively. The DNA binding studies of the complexes were investigated using electronic absorption spectroscopy and fluorescence quenching. The absorption spectral titrations of the complexes with DNA indicate that the CT-DNA binding affinity (K_b) of complex 1 (2.10(±0.07) × 10⁶ M⁻¹) is slightly greater than that of 2 (1.11(±0.04) × 10⁶ M⁻¹). From fluorescence spectra the apparent binding constant (K_app) values were calculated and they are found to be 5.41(±0.01) × 10⁵ M⁻¹ for 1 and 3.93(±0.02) × 10⁵ M⁻¹ for 2. The molecular dynamics simulation demonstrates that the Zn(ii) complex 1 is a good intercalator of DNA.

A binuclear and a tetranuclear zinc(ii) of pyruvaldehyde thiosemicarbazone show selective sensing of ATP at pH 7.4 (0.01 M HEPES) in CH₃CN–H₂O (9 : 1) medium. The DNA binding and phosphatase activities of the complexes are also reported.     

N-doped porous carbons derived from Zn-porphyrin-MOF

N-doped porous metal–organic framework (MOF)-derived carbons (MDCs) were directly synthesized from a new Zn-DpyDtolP-MOF (ZnDpyDtolP·1/2DMF, H₂DpyDtolP = 5,15-di(4-pyridyl)-10,20-di(4-methylphenyl)porphyrin) containing a 3D hexagonal network through a self-templated carbonization method. KOH-activated MDC derivatives denoted as MDC-700-nKOH were also prepared with different weight ratios of KOH activator to MDC (MDC : KOH = 1 : n, where n = 1, 2). Compared to bare MDC, MDC-700-nKOH showed effective improvements of both gas sorption and electrochemical capacitive properties. More developed microporosity by KOH activation might induce great enhancement of high operating capacitive performances. The N-doped MDC-700-2KOH had high maximum gravimetric specific capacitance (555.6 F g⁻¹) and specific energy (40.4 W h kg⁻¹) at 0.1 A g⁻¹ in 1 M H₂SO₄. Even at a high current density of 190 A g⁻¹ in 6 M KOH, it exhibited high capacitive performance with a large specific power of 80 423 W kg⁻¹. MDC-700-nKOH electrodes also showed good recycling properties of electrochemical capacitance up to 30 000 cycles.

The porphyrin-based Zn-MOF is directly carbonized and activated by KOH for the generation of N-doped porous carbons acting as high performance supercapacitor electrode materials.     

Combined algicidal effect of urocanic acid,N-acetylhistamine and l-histidine to harmful alga Phaeocystis globosa

The algicidal compounds produced by Bacillus sp. strain B1 against Phaeocystis globosa, one of the main red-tide algae, were isolated and identified in a previous study as urocanic acid (uro), l-histidine (his) and N-acetylhistamine (ace). The 96 h median effective concentration EC₅₀ values indicated the algicidal effect order of uro (8 μg mL⁻¹) > ace (16 μg mL⁻¹) > his (23 μg mL⁻¹). The interaction between uro and ace had a synergistic effect on Phaeocystis globosa, accelerated the increase in its intracellular reactive oxygen species (ROS) levels, and further decreased the activities of antioxidases after 96 h, causing destruction of cell membrane integrity and nuclear structure. However, the other two binary mixtures uro + his and ace + his were both antagonistic to Phaeocystis globosa. The increase in the level of ROS indicated that the algal cells suffered from oxidative damage. The surplus ROS induced the increase in malondialdehyde (MDA) content and activities of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT), all of which reached maxima after 72 h treatment. Transmission electron microscopy (TEM) analysis revealed that these nitrogen-containing compounds caused destruction of cell membrane integrity, chloroplasts and nuclear structure. The present study will provide useful information for the combined effect of algicidal compounds on the harmful alga Phaeocystis globosa. This is the first report to explore single and combined algicidal effects of three nitrogen-containing compounds against the harmful alga Phaeocystis globosa.

Ultrastructure of Phaeocystis globosa cells after treatment with EC₅₀ value for 72 h: (a) control, (b) ace (16 μg mL⁻¹), (c) uro (8 μg mL⁻¹), (d) uro + ace (1 : 1 TU, 8 : 16 μg mL⁻¹) Chl, chloroplast; CW, cell wall; N, nucleus; PM, plasma membrane.