Construction and analytical application of a biosensor based on stearic acid-graphite powder modified with sweet potato tissue in organic solvents

A biosensor based on stearic acid-graphite powder modified with sweet potato (Ipomoea batatas (L.) Lam.) tissue as peroxidase source was constructed and applied in organic solvents. Several parameters were studied to evaluate the performance of this biosensor such as stearic acid-graphite powder and tissue composition, type and concentration of supporting electrolyte, organic solvents, water/organic solvent ratio (% v/v) and hydrogen peroxide concentration. After selection of the best conditions, the biosensor was applied for the determination of hydroquinone in cosmetic creams in methanol. At the peroxidase electrode hydroquinone is oxidized in the presence of hydrogen peroxide and the radical formed was reduced back electrochemically at –180 mV vs Ag/AgCl (3.0 mol L^–1 KCl). The reduction current obtained was proportional to the concentration of hydroquinone from 6.2 × 10^–5 to 1.5 × 10^–3 mol L^–1 (r = 0.9990) with a detection limit of 8.5 × 10^–6 mol L^–1. The recovery of hydroquinone from two samples ranged from 98.8 to 104.1% and an RSD lower than 1.0% for a solution containing ¶7.3 × 10^–4 mol L^–1 hydroquinone and 1.0 × 10^–3 mol L^–1 hydrogen peroxide in 0.10 mol L^–1 tetrabutylammonium bromide methanol-phosphate buffer solution (95:5% v/v) (n = 10) was obtained.     

Synthesis,Crystal Structure,and Enhancement of the Efficacy of Metronidazole Against Entamoeba histolytica by Complexation with Palladium(II), Platinum(II), or Copper(II)

Reaction of trans‐[PdCl₂(DMSO)₂], cis‐[PtCl₂(DMSO)₂], and [Cu(OAc)₂]⋅H₂O with metronidazole (mnz) leads to the formation of new complexes, i.e., trans‐[PdCl₂(mnz)₂] ( 1 ), trans‐[PtCl₂(mnz)₂] ( 2 ), and trans‐[Cu₂(OAc)₄(mnz)₂] ( 3 ), respectively. Complexes 1 – 3 crystallize all in the centrosymmetric monoclinic space group P2₁/c with Z=8. Unit‐cell parameters for these complexes are: 1 , a=7.1328(14) Å, b=20.699(4) Å, c=7.1455(14) Å, and β=116.17(3)°; 2 , a=6.9169(14) Å, b=21.853(4) Å, c=6.7218(13) Å, and β=110.79(3)°; 3 , a=9.1663(18) Å, b=19.129(4) Å, c=8.9446(18) Å, and β=116.44(3)°. The complexes 1 and 2 maintain an ideal square‐planar geometry. In complex 3 , the H₂O molecules of the starting complex are replaced by metronidazole while maintaining a dimeric structure of [Cu(OAc)₂]. Each Cu ion has an ideal octahedral structure, though distortion occurs in the equatorial position where the acetato ligands are attached. The Cu Cu separation of 2.6343(8) Å indicates considerable metal‐metal interaction. The testing of the antiamoebic activity of these complexes against the protozoan parasite Entamoeba histolytica suggests that compound 1 – 3 might be endowed with important antiamoebic properties since they showed IC₅₀ values in a μM range better than metronidazole (Table 2). Thus, compound 1 displayed more effective amoebicidal activity than metronidazole (IC₅₀ values of 0.103 μM vs. 1.50 μM , resp.).     

Biocidal Activity of a Nanoemulsion Containing Essential Oil from Protium heptaphyllum Resin against Aedes aegypti (Diptera: Culicidae)

This work aimed to prepare a nanoemulsion containing the essential oil of the Protium heptaphyllum resin and evaluate its biocidal activities against the different stages of development of the Aedes aegypti mosquito. Ovicide, pupicide, adulticide and repellency assays were performed. The main constituents were p-cymene (27.70%) and α-pinene (22.31%). The developed nanoemulsion showed kinetic stability and monomodal distribution at a hydrophilic–lipophilic balance of 14 with a droplet size of 115.56 ± 1.68 nn and a zeta potential of −29.63 ± 3.46 mV. The nanoemulsion showed insecticidal action with LC₅₀ 0.404 µg·mL⁻¹ for the ovicidal effect. In the pupicidal test, at the concentration of 160 µg·mL⁻¹, 100% mortality was reached after 24 h. For adulticidal activity, a diagnostic concentration of 200 µg·mL⁻¹ (120 min) was determined. In the repellency test, a concentration of 200 µg·mL⁻¹ during the 180 min of the test showed a protection index of 77.67%. In conclusion, the nanobiotechnological product derived from the essential oil of P. heptaphyllum resin can be considered as a promising colloid that can be used to control infectious disease vectors through a wide range of possible modes of applications, probably as this bioactive delivery system may allow the optimal effect of the P. heptaphyllum terpenes in aqueous media and may also induce satisfactory delivery to air interfaces.     

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.     

Lipid Droplets in Cancer: From Composition and Role to Imaging and Therapeutics

Cancer is the second most common cause of death worldwide, having its origin in the abnormal growth of cells. Available chemotherapeutics still present major drawbacks, usually associated with high toxicity and poor distribution, with only a small fraction of drugs reaching the tumour sites. Thus, it is urgent to develop novel therapeutic strategies. Cancer cells can reprogram their lipid metabolism to sustain uncontrolled proliferation, and, therefore, accumulate a higher amount of lipid droplets (LDs). LDs are cytoplasmic organelles that store neutral lipids and are hypothesized to sequester anti-cancer drugs, leading to reduced efficacy. Thus, the increased biogenesis of LDs in neoplastic conditions makes them suitable targets for anticancer therapy and for the development of new dyes for cancer cells imaging. In recent years, cancer nanotherapeutics offered some exciting possibilities, including improvement tumour detection and eradication. In this review we summarize LDs biogenesis, structure and composition, and highlight their role in cancer theranostics.     

Spectrophotometric determination of methyldopa and dopamine in pharmaceutical formulations using a crude extract of sweet potato root (Ipomoea batatas (L.) Lam.) as enzymatic source

A rapid, precise and low cost spectrophotometric method is proposed for the determination of methyldopa and dopamine in pharmaceutical formulations. The crude extract of sweet potato root (Ipomoea batatas (L.) Lam.) was used as an enzymatic source of polyphenol oxidase (PPO; EC.1.14.18.1). This enzyme catalyses the oxidation of catecholamines to the corresponding methyldopaquinone and dopaminequinone. Those compounds are converted by a rapid spontaneous auto-oxidation to methyldopachrome and dopaminechrome which have a strong absorption at 480 or 470 nm, respectively. The calibration graphs are linear from 2.0x10(-4) to 6.0x10(-3) M. The results obtained by the proposed enzymatic method are in close agreement with those obtained using a Pharmacopoeia procedure and also with the label values. The detection limit (three times the signal blank/slope) was 3.4x10(-5) and 3.0x10(-5) M for methyldopa and dopamine, respectively, the recovery of methyldopa and dopamine from three samples ranged from 97.5 to 102.9% of the added amount.     

Analytic k-Linearizability of Some Resonant Poisson Structures

We consider analytic Poisson tensors P whose associated Lie algebra at a singular point is resonant (in the sense of J. P. Dufour (J. Differential Geom. 30 (1990), 415–428)). We give sufficient conditions on the k-jet of P at the given point so that P is analytically linearizable.     

A general route for the synthesis of hydrido-carboxylate complexes of the type MH(CO)(κ-OCOR)(PPh3)2 [M = Ru,Os; R = CH3, CH2Cl,C6H5, CH(CH3)2] and their use as precatalysts for hydrogenation and hydroformylation reactions

The synthesis and solid-state IR, ¹H and ³¹P{¹H} NMR spectroscopic characterization of complexes of the type MH(CO)(κ³-OCOR)(PPh₃)₂ [M = Ru, Os; R = CH₃, CH₂Cl, C₆H₅ and CH(CH₃)₂] are reported in this paper. These compounds were obtained by reaction of the respective cationic complex [MH(CO)(NCMe)₂(PPh₃)₂]BF₄ with the sodium salt of the corresponding carboxylic acid in a 1:1 v/v dichloromethane/methanol solution at room temperature. The spectroscopic data of these complexes and some DFT calculations reveal an octahedral geometry with a bidentated carboxylate, two equivalent triphenylphosphines in a mutually trans positions, a linear hydride and a linear carbonyl both in the cis-positions of the coordination sphere. The catalytic results indicate that these complexes are efficient and regioselective precatalysts for the quinoline hydrogenation and for the hydroformylation of 1-hexene, under mild reaction conditions (130 °C and 4 atm H₂ and 120 °C and 15 atm H₂/CO, respectively). For benzothiophene hydrogenation, the osmium complexes showed low activities whereas the analogous ruthenium complexes were catalytically inactive under somewhat more drastic reaction conditions to those of the quinoline hydrogenation (140 °C and 10 atm H₂).     

Piperidine-Iodine as Efficient Dual Catalyst for the One-Pot,Three-Component Synthesis of Coumarin-3-Carboxamides

A simple and efficient one-pot, three-component synthetic method for the preparation of coumarin-3-carboxamides was carried out by the reaction of salicylaldehyde, aliphatic primary/secondary amines, and diethylmalonate. The protocol employs piperidine-iodine as a dual system catalyst and ethanol, a green solvent. The main advantages of this approach are that it is a metal-free and clean reaction, has low catalyst loading, and requires no tedious workup.