Ethanolic KOH Research Articles

Novel diphenyl ether-heterocycles hybrids: Synthesis via Hantzsch and Biginelli reactions, molecular docking simulation, and antimicrobial activities

By reacting the potassium salt produced by treating 4-hydroxybenzaldehyde with ethanolic KOH with 4-fluorobenzaldehyde in DMF at reflux, 4,4′-oxydibenzaldehyde was produced. The Hantzsch reaction of 4,4′-oxydibenzaldehyde with the respective 3-aminocrotononitrile or a mixture of 1,3-dicarbonyl compounds and amine source yielded novel bis-1,4-dihydropyridin-3,5-dicarbonitrile, bis-hexahydroacridine-1,8-dione, and bis-decahydropyrimido[4,5-b]quinoline. Bis-hexahydrobenzo[4,5]imidazo[2,1-b]quinazoline and bis(tetrahydro[1,2,4]triazolo[5,1-b]quinazolin-8(4H)-one) were obtained via Biginelli-like reaction of 4,4′-oxydibenzaldehyde with both dimedone and 4H-1,2,4-triazol-3-amine or 1H-benzo[d]imidazol-2-amine, respectively. By reacting 2,2′-((oxybis(4,1-phenylene))bis(methanylylidene))bis(hydrazinecarbothioamide) with the appropriate 2-bromoacetyl derivative or α-keto-hydrazonoyl chloride in ethanol containing TEA, novel bis-thiazoles with diphenyl ether cores were successfully obtained. Antibacterial activity against several bacterial strains was investigated for all of the produced compounds. Compound 13b demonstrated good antibacterial activity against B. subtilis. A molecular docking study was done against gram-positive thymidylate kinase and bacterial DNA gyrase B to determine the mechanism of action of the active compounds.

Three‐component synthesis of arene‐linked pyrazolo[1,5‐a]pyrimidines

AbstractIn this study, we aimed to establish an efficient method for synthesizing two new series of arene‐linked pyrazolo[1,5‐a]pyrimidines. This was achieved by reacting 1H‐pyrazole‐3,5‐diamines with the respective acetophenones and benzaldehydes in a 1:1:1 ratio. To optimize this three‐component reaction, various bases, and solvents were investigated. Use of two equivalents of KOH in ethanol at reflux for 4–6 h resulted in 89%–96% yields of the desired products. Structure of new products was elucidated by considering their elemental and spectral data.

Design and synthesis of novel nitrothiazolacetamide conjugated to different thioquinazolinone derivatives as anti-urease agents

The present article describes the design, synthesis, in vitro urease inhibition, and in silico molecular docking studies of a novel series of nitrothiazolacetamide conjugated to different thioquinazolinones. Fourteen nitrothiazolacetamide bearing thioquinazolinones derivatives (8a-n) were synthesized through the reaction of isatoic anhydride with different amine, followed by reaction with carbon disulfide and KOH in ethanol. The intermediates were then converted into final products by treating them with 2-chloro-N-(5-nitrothiazol-2-yl)acetamide in DMF. All derivatives were then characterized through different spectroscopic techniques (1H, 13C-NMR, MS, and FTIR). In vitro screening of these molecules against urease demonstrated the potent urease inhibitory potential of derivatives with IC50 values ranging between 2.22 ± 0.09 and 8.43 ± 0.61 μM when compared with the standard thiourea (IC50 = 22.50 ± 0.44 μM). Compound 8h as the most potent derivative exhibited an uncompetitive inhibition pattern against urease in the kinetic study. The high anti-ureolytic activity of 8h was confirmed against two urease-positive microorganisms. According to molecular docking study, 8h exhibited several hydrophobic interactions with Lys10, Leu11, Met44, Ala47, Ala85, Phe87, and Pro88 residues plus two hydrogen bound interactions with Thr86. According to the in silico assessment, the ADME-Toxicity and drug-likeness profile of synthesized compounds were in the acceptable range.

One‐Pot Synthesis of Organic Carbonate from Alcohol and Alkyl Bromide under Low CO2 Pressure

AbstractA mild and highly efficient approach has been developed for the one‐pot synthesis of organic carbonate from CO2, alcohol and alkyl bromide using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) as the activator. The conditions of template reaction were screened and the corresponding product butyl methyl carbonate (BMC, 1), was obtained with a high yield of 95 % in 1 h. The reaction system can be extended for the synthesis of organic carbonates from a broad range of alcohols and alkyl bromides with excellent yields under low CO2 pressure. DBU was proved to be recyclable after having been treated with KOH in ethanol. In addition, a plausible mechanism of this reaction was proposed according to the present results and literature reports.

Synthesis of 2-aryl/alkyl-3-thio-5-dimethyl amino-7-imino-1, 2, 4, 6-tetra-azepines, structural studies and screening for antibacterial and antifungal activities

2-aryl/alkyl-3-thio-5-dimethyl amino-7-imino-1,2,4,6-tetra-azepines were synthesized from 1,2,4,6 thiatriazepines by refluxing for 1 hour with 5% ethanolic KOH. The 1,2,4,6 thiatriazepines were obtained by cyclization reaction from medicinally important metformin hydrochloride and RNCSCI2. These 1,2,4,6-tetra-azepines were characterized by spectral and analytical studies. From these synthesized compounds, those with substituents phenyl, p-chlorophenyl and o-anisyl showed high sensitivity towards E.coli when they were screened for their antibacterial and antifungal activities using E coli, S.aures, A.niger and C albicans Graphical Where R above are in a) p-tolyl, b) o-tolyl, c) phenyl, d) p-chloro phenyl e)o-chloro phenyl, f) m-chloro phenyl, g) p-anisyl, h) o-anisyl, i) t-butyl

Synthesis and Antimicrobial Activity of Some New Coumarin Incorporated Pyridine-3-carbonitrile Derivatives

Drug resistance causes serious difficulties in the routine therapy for curing common microbial infections. Thus it is very essential to develop new antimicrobial agents which can offer alternative treatments. The development of potent and effective antimicrobial agents is of utmost importance to overcome the emerging multidrug resistance strains of bacteria and fungi. The technique involves Knoevenagel reaction between substituted salicylaldehyde and ethyl acetoacetate in presence of piperidine as catalyst to give 3-acetyl coumarin. The intermediate coumarinyl chalcones was synthesized by condensing with various substituted benzaldehyde in presence of ethanolic KOH. The final synthesized pyridine-3-carbonitrile derivative was prepared upon refluxing with coumarinyl chalcones with malononitrile in presence of ammonium acetate. All the newly synthesized compounds were assigned on the basis of IR, 1H NMR and mass spectral data. The finalsynthesized compounds were screened for their antibacterial activity tube dilution method. Most of the compounds showed promising MIC by tube dilution method as compared to standard Cephalosporin.

Synthesis, characterization, DFT and TD-DFT study of novel bis(5,6-diphenyl-1,2,4-triazines)

Due to the numerous biological as well as pharmacological activities of 1,2,4-triazine derivatives, we reported a synthesis of novel series of bis(5,6-diphenyl-1,2,4-triazines) via alkylation of 5,6-diphenyl-1,2,4-triazine-3(4H)-thione with the appropriate bis(halo) compounds in ethanolic KOH. The chemical structures of these compounds were confirmed by spectroscopic techniques. The absorption and excited-emission spectra of the studied novel series were monitored experimentally in ethanol solvent. The molecular structures of these triazines were optimized using B3LYP/6–31G(d) level of theory. The electronic absorption and emission spectra of the novel compounds, in gas and ethanol solvent, were calculated using time dependent density functional theory (TDDFT) at mPW1PW91/ 6–31 G (d) level. The obtained theoretical results were compared to experimental ones. The results show that, the computational optical properties of the studied novel series are in agreement with experimental results.

Synthesis and antimicrobial activity of new 1,2,4‐triazole, 1,3,4‐oxadiazole, 1,3,4‐thiadiazole, thiopyrane, thiazolidinone, and azepine derivatives

Abstract4‐oxo‐4‐phenylbutanehydrazide 3 was reacted with aryl or alkyl isothiocyanates to give the corresponding N‐substituted‐2‐(4‐oxo‐4‐phenylbutanoyl) hydrazine‐1‐carbothioamide 4a‐c. Cyclization of thiosemicarbazides 4a‐c with sodium hydroxide led to the formation of 3‐(4‐sub‐5‐thioxo‐1,2,4‐triazol‐3‐yl)‐propanone 5a‐c. Desulfurization of thiosemicarbazides 4a‐c by mercuric oxide afforded 3‐(5‐(sub‐amino)‐1,3,4‐oxadiazol‐2‐yl)‐propanone 6a‐c. The reaction of 4a‐c with phosphorus oxychloride gave 3‐(5‐(sub‐amino)‐1,3,4‐thiadiazol‐2‐yl)‐propanone 7a‐c. Treatment of 4a‐c with ethyl‐bromoacetate or α‐bromopropionic acid gave N′‐(3‐sub‐thiazolidin‐2‐ylidene)‐butanehydrazide 8a‐c and (N′‐(3‐sub‐oxothiazolidin‐2‐ylidene)‐butanehydrazide 9a‐c. Chlorination of oxothiazolidine‐hydrazide 9a‐c by phosphorus oxychloride afforded N‐(3‐sub‐4‐oxothiazolidine)‐butane‐hydrazonoyl‐chloride 10a‐c. The reaction of 10a‐c with mercaptoacetyl‐chloride yielded 2‐((4‐benzoyl‐thiopyrane) hydrazono)‐3‐sub‐thiazolidinone 11a‐c. Also, reacted of 10a‐c with hydrazine hydrate afforded N″‐(3‐sub‐oxothiazolidine)‐butane‐hydrazon‐hydrazide 12a‐c. The 3‐sub‐2‐((pyridazine) hydrazono) thiazolidinone 13a‐c was obtained by cyclization of 12a‐c via refluxing in DMF. The reaction and cyclized of 9a‐c with chloroacetyl‐chloride in ethanolic KOH afforded 1‐((3‐sub‐4‐oxothiazolidine) amino)‐azepine‐dione 14a‐c. The chemical structures of the new compounds have been confirmed by diverse spectroscopy analyses such as IR, NMR, MS, and elemental analysis. The synthesized compounds were tested for their antimicrobial activity and these compounds were considered (Pyridazin‐hydrazono‐thiazolidinone 13a‐c, oxothiazolidin‐azepinedione 14a‐c, N‐thiazolidin‐hydrazon‐hydrazide 12a‐c, and thiopyran‐hydrazono‐thiazolidinone 11a‐c) the most effective as antimicrobial activity.

Synthesis, In Vitro Anti-HIV Activity, Cytotoxicity, and Computational Studies of Some New Steroids and Their Pyrazoline and Oxime Analogues

There is an urgent need for the design and development of new and safer drugs for the treatment of HIV infection, active against the currently resistant viral strains by development of new non-nucleoside reverse transcriptase inhibitors (NNRTIs). A series of pregnenolone analogues, 3-((aryl)-1-(5-pregnen-3β-ol-17-yl)prop-2-en-1-ones, were synthesized. Further, treatment of 3-((4-bromo-, 4-trifluoromethyl, or 4-methylphenyl)-1-(preg-5-en-3β-ol-17-yl)prop-2-en-1-ones with thiosemicarbazide in ethanolic KOH or hydrazine hydrate in HOAc gave 5-(4-bromo-, 4-trifluoromethyl, or 4-methylphenyl)-3-(preg-5-en-3β-ol-17-yl)-4,5-dihydro-1H-pyrazoline-1-carbothioamides and 1-O-acetyl-(5-(4-bromophenyl)-3-(preg-5-en-3β-ol-17-yl)-4,5-dihydro-1H-pyrazoline, respectively. Analogously, treatment of 3-((4-bromophenyl)-1-(preg-5-en-3β-ol-17-yl)prop-2-en-1-one with hydroxylamine afforded the Z/E isomers of 3-(4-bromophenyl)-1-(preg-5-en-3β-ol-17-yl)prop-2-en-1-one oxime. The new compounds were assayed against HIV-1 and HIV-2 in MT-4 cells. Compounds 3-(thiophene-2-yl)-1-(preg-5-en-3β-ol-17-yl)prop-2-en-1-one and 1-O-acetyl-(5-(4-bromophenyl)-3-(preg-5-en-3β-ol-17-yl)-4,5-dihydro-1H-pyrazoline were the most active in inhibiting HIV-1 and HIV-2 with IC50 = 60.5 μM (SI > 2, against HIV-2 and SI 0.29 μM (SI < I), respectively, suggesting to be new leads in the development of antiviral agents. QSAR of 3-((aryl)-1-(5-pregnen-3β-ol-17-yl)prop-2-en-1-ones and 5-(substituted phenyl)-3-(5-preg-5-3β-ol-17-yl)-4,5-dihydro-1H-pyrazole-1-carbothioamides has been studied. The conformational analysis of 5-(4-trifluoromethylphenyl)-3-(preg-5-en-3β-ol-17-yl)-4,5-dihydro-1H-pyrazoline-1-carbothioamide and 1-O-acetyl-(5-(4-bromophenyl)-3-(preg-5-en-3β-ol-17-yl)-4,5-dihydro-1H-pyrazoline as well as the molecular docking study of the latter compound have been investigated.

Synthesis of 2-(1,3-Diphenyl-1H-1,2,4-triazol-5-yl)-2,2-dinitroacetonitrile and Its Reaction with Diazomethane

A method for the synthesis of 2-(1,3-diphenyl-1H-1,2,4-triazol-5-yl)-2,2-dinitroacetonitrile was developed, and its reaction with diazomethane was investigated to show the reaction involves 1,3-dipolar cycloaddition and forms a separable mixture of 4-[(1,3-diphenyl-1H-1,2,4-triazol-5-yl)dinitromethyl]-2H-1,2,3-triazoles. The latter react with KOH in ethanol to form potassium salts of 4-[(1,3-diphenyl-1H-1,2,4-triazole-5-yl)aci-nitromethyl]-1,2,3-triazoles.

Ultrasound-assisted synthesis of novel chalcone, heterochalcone and bis-chalcone derivatives and the evaluation of their antioxidant properties and as acetylcholinesterase inhibitors

The chalcone and bis-chalcone derivatives have been synthesized under sonication conditions via Claisen-Schmidt condensation with KOH in ethanol at room temperature (20–89%). The structures were established on the basis of NMR, IR, Single-crystal XRD, and MS. The best compound 3u had inhibitory activity (IC50 = 7.50 µM). The synthesis, the antioxidative properties, chemical reactivity descriptors supported in Density Functional Theory (DFT), acetylcholinesterase (AChE) inhibition and their potential binding modes, and affinity were predicted by molecular docking of a number of morpholine-chalcones and quinoline-chalcone. A series of bis-chalcones are also reported. Molecular docking and an enzyme kinetic study on compound 3u suggested that it simultaneously binds to the catalytic active site (CAS) and peripheral anionic site (PAS) of AChE. Moreover, the pharmacokinetic profile of these compounds was investigated using a computational method.

Deacylative 1,6-addition of Bestmann-Ohira reagent to p-quinone methides for the synthesis of α-diazo-β-diarylphosphonates and cis-stilbenyl phosphonates

The role of Bestmann-Ohira Reagent (BOR) as a conjugate addition partner is reported for the first time. Deacylation of BOR in the presence of ethanolic KOH and 1,6-addition of the resulting diazophosphonate anion to p-quinone methides (PQMs) provides β-disubstituted α-diazophosphonates in good to excellent yields in most cases. Such 1,6-adducts further undergo Rh-catalyzed elimination of the diazo group and 1,2-migration of the phenolic group to afford cis-stilbenylphosphonates with high E-selectivity. The migration of the phenolic group presumably takes place via a spirocyclopropane intermediate derived from the Rh-carbenoid.

Synthesis of Novel 3(N,N-dialkylamino)alkyl/phenyl Substituted Thieno [2,3-d]pyrimidinones as H1-Anti-Histaminic and Antimicrobial Agents

Background: Thienopyrimidines are the bioisoster of quinazoline and unlike quinazoline exist in three isomeric forms corresponding to the three possible types annulation of thiophene to the pyrimidine ring viz thieno[2,3-d] pyrimidine, thieno[3,2-d] pyrimidine and thieno[3,4-d]pyrimidine. Heterocyclic containing the thienopyrimidinone moiety exhibits various pronounced activities such as anti-hypertensive, analgesic and anti-inflammatory, antiviral, platelet aggregation inhibitory, antiprotozoal bronchodilatory, phosphodiesterase inhibitory, antihistaminic, antipsychotic and antimicrobial activity. Objective: Synthesis of novel 3(N,N-dialkylamino)alkyl/phenyl substituted thieno[2,3-d]pyrimidinones as H1-anti-histaminic and antimicrobial agents. Methods: A series of 3-[(N,N-dialkylamino)alkyl/phenyl]-2-(1H)thioxo-5,6,7,8-tetrahydrobenzo(b) thieno(2,3-d)pyrimidine-4(3H)-ones[4a-d], their oxo analogous [5a-d] and 3-[(N,N-dialkylamino)alkyl]- 2-chlorophenyl-5,6,7,8-tetrahydrobenzo(b)thieno(2,3-d)pyrimidine- 4 (3H)-ones[6a-d]derivative were synthesized from 2-amino-4,5,6,7-tetrahydrobenzo(b)thiophene-3-carboxylic acid by nucleophilic substitution of different N,N-dialkyl alkylene/phenylene diamines on activated 3-acylchloride moiety followed by cyclocondensation with carbon disulfide and ethanolic potassium hydroxide to get [4a-d] and in second reaction by condensation with 4-chlorobenzoyl chloride to get [6a-d] by single pot novel innovative route. The oxo analogous [5a-d] were prepared by treating derivatives [4a-d] with potassium permagnate in ethanolic KOH. The synthesized compound were evaluated for H1-antihistaminic and antimicrobial activities. Results: All synthesized compounds exhibited significant H1-antihistaminic activity by in vitro and in vivo screening methods and data were verified analytically and statistically. The compound 4a, 4b, 5a and 5b showed significant H1-antihistaminiic activity than the reference standard chlorpheniramine maleate. The compound 6d, 6c, 5c and 4c exhibited significant antimicrobial activity.

An Efficient, Large-Scale Synthesis of Cytenamide

Dibenzosuberenone (5 H-dibenzo[a,d]cyclohepten-5-one) was reduced to the corresponding alcohol by sodium borohydride/MeOH and converted to the corresponding 5-chloro compound by thionyl chloride/benzene, treatment of which with CuCN/toluene gave the corresponding nitrile. Hydrolysis by ethanolic KOH yielded the corresponding amide, cytenamide (5 H-dibenzo[a,d]cycloheptene-5-carboxamide).

Impaired Rhodopsin Generation in the Rat Model of Diabetic Retinopathy

Diabetic retinopathy is a common complication of diabetes mellitus. Diabetic patients experience functional deficits in dark adaptation, contrast sensitivity, and color perception before microvascular pathologies become apparent. Herein, we evaluated early changes in neural retinal function and in retinoid metabolism in the eye in diabetes. Streptozotocin-induced diabetic rats showed decreased a- and b-wave amplitudes of scotopic and photopic electroretinography responses 4 months after diabetes induction compared to nondiabetic controls. Although Western blot analysis revealed no difference in opsin expression, rhodopsin content was decreased in diabetic retinas, as shown by a difference in absorbance. Consistently, levels of 11-cis-retinal, the chromophore for visual pigments, were significantly lower in diabetic retinas compared to those in controls, suggesting a retinoid deficiency. Among visual cycle proteins, interphotoreceptor retinoid-binding protein and stimulated by retinoic acid 6 protein showed significantly lower levels in diabetic rats than those in nondiabetic controls. Similarly, serum levels of retinol-binding protein 4 and retinoids were significantly lower in diabetic rats. Overall, these results suggest that retinoid metabolism in the eye is impaired in type 1 diabetes, which leads to deficient generation of visual pigments and neural retinal dysfunction in early diabetes.

Combining Sustainable Synthesis of a Versatile Ruthenium Dihydride Complex with Structure Determination Using Group Theory and Spectroscopy

A good-yielding two-step synthesis of RuH2(CO)(PPh3)3 using conventional or microwave-assisted reflux techniques is described for use in undergraduate teaching laboratories. RuH2(CO)(PPh3)3 is synthesized from RuCl3·xH2O, PPh3, and KOH in ethanol in two steps under an inert atmosphere or using a one-pot microwave-assisted reflux to reduce the reaction time to approximately 10 min. This makes this useful compound readily available within an undergraduate laboratory session via efficient and sustainable syntheses, enabling learning outcomes associated with air-sensitive synthesis and application of group theory and spectroscopy to structure determination to be achieved.

Cultivation of Nannochloropsis oculata in centrate and conversion of its lipids to biodiesel in a low-cost microwave reactor

ABSTRACTIn the present study, 100% centrate (wastewater generated in the sludge centrifuge of a municipal wastewater treatment plant) was used for the cultivation of microalga Nannochloropsis oculata in a lab scale externally illuminated photobioreactor. Cells were harvested at the end of the exponential phase and the resulting wet algal biomass (80 wt % moisture) was subjected to direct saponification in a low-cost microwave reactor using ethanolic KOH to convert the algal lipids to soap. The soap was separated from other unsaponifiable matter by precipitation using saturated KCl and subjected to simultaneous acidulation and esterification to form biodiesel of high purity (97.04% FAME in final biodiesel). Optimum values of esterification of fatty acids in microwave reactor were: microwave power-450 W, molar ratio of methanol to fatty acids -80:1, concentration of sulphuric acid-2.5 wt %, reaction time-11 min and reaction temperature-60 °C. Kinetics studies of esterification conducted under these conditions revealed that the rate constant was high (0.452 min−1). The final yield of biodiesel was 97.11%. Cetane number and oxidation stability index of biodiesel were evaluated to be 59.349 and 3.298 h respectively. Removal rates of Chemical oxygen demand (COD), total nitrogen and total phosphorous were 82.65%, 62.25% and 52.65% respectively.

Ru-Catalyzed Estragole Isomerization under Homogeneous and Ionic Liquid Biphasic Conditions.

The isomerization of estragole to trans-anethole is an important reaction and is industrially performed using an excess of NaOH or KOH in ethanol at high temperatures with very low selectivity. Simple Ru-based transition-metal complexes, under homogeneous, ionic liquid (IL)-supported (biphasic) and “solventless” conditions, can be used for this reaction. The selectivity of this reaction is more sensitive to the solvent/support used than the ligands associated with the metal catalyst. Thus, under the optimized reaction conditions, 100% conversion can be achieved in the estragole isomerization, using as little as 4 × 10–3 mol % (40 ppm) of [RuHCl(CO)(PPh3)3] in toluene, reflecting a total turnover number (TON) of 25 000 and turnover frequencies (TOFs) of up to 500 min–1 at 80 °C. Using a dimeric Ru precursor, [RuCl(μ-Cl)(η3:η3-C10H16)]2, in ethanol associated with P(OEt)3, a TON of 10 000 and a TOF of 125 min–1 are obtained with 100% conversion and 99% selectivity. These two Ru catalytic systems can be transposed to biphasic IL systems by using ionic-tagged P-ligands such as 1-(3-(diphenylphosphanyl)propyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide immobilized in 1-(3-hydroxypropyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl) imide with up to 99% selectivity and almost complete estragole conversion. However, the reaction is much slower than that performed under solventless or homogeneous conditions. The use of ionic-tagged ligands significantly reduces the Ru leaching to the organic phase, compared to that in reactions performed under homogeneous conditions, where the catalytic system loses catalytic performance after the second recycling. Detailed kinetic investigations of the reaction catalyzed by [RuHCl(CO)(PPh3)3] indicate that a simplified kinetic model (a monomolecular reversible first-order reaction) is adequate for fitting the homogeneous reaction at 80 °C and under biphasic conditions. However, the kinetics of the reaction are better described if all of the elementary steps are taken into consideration, especially at 40 °C.

ESTUDO DA EXTRAÇÃO DE CORANTE NATURAL QUE CONFERE PROTEÇÃO ULTRAVIOLETA EM FIBRAS NATURAIS

Neste trabalho estudaram-se parâmetros do processo de extração de bixina e norbixina a partir do urucum e a proteção ultravioleta conferida pelo corante à uma fibra natural. Avaliaram-se diferentes solventes de extração: acetona, acetato de etila, KOH em solução e etanol, bem como as misturas entre eles. Analisaram-se os efeitos de: temperatura (30 a 60oC); tamanho do sólido (semente intacta e moída); tempo de extração e razão mássica sólido/solvente nas proporções de 0,125, 0,25 e 0,42. Com os resultados obtidos verificou-se uma melhor extração utilizando-se a mistura etanol:acetona 50% (v/v), temperatura de 55ºC e tamanho da partícula de 100 MESH. A partir dos parâmetros adotados foi possível concluir que houve a saturação do solvente em 20 minutos de extração e com isso, concluiu-se que o sólido pode ser aproveitado para mais de um ciclo de extração. Verificou-se uma proteção ultravioleta conferida pelo corante aplicado no algodão alvejado de 89% da radiação ultravioleta absorvida.

Synthesis and in vitro anticancer evaluation of 1,4-phenylene-bis-pyrimidine-2-amine derivatives

A series of 1,4-phenylene-bis-chalcones 3a-3h were synthesized by the reaction of terephthalaldehyde with substituted arylketones in this study. The novel 1,4-phenylene-bis-pyrimidine-2-amine derivatives 5a-5h were obtained by the addition of guanidine hydrochloride to 1,4-phenylene-bis-chalcone 3a-3h in ethanolic KOH under reflux conditions. The structure of the compounds was explained by means of IR, $^{1}$H NMR, $^{13}$C NMR, and elemental analyses. The anticancer activities of 3a-3h and 5a-5h were investigated against rat brain tumor cells and human uterus carcinoma in vitro$.$ Activity tests were performed as dose-dependent assays at eight concentrations. The positive control was 5-fluorouracil (5-FU). Compounds 3c and 3d were examined and they showed high activities as compared to 5-FU against C6 (rat brain tumor) and HeLa (human uterus carcinoma) cells. The anticancer activity of 5h was better than that of 5-FU at high concentrations cell-selectively against C6 cells.