Microwave-assisted synthesis and biological evaluation of new thiazolylhydrazone derivatives as tyrosinase inhibitors and antioxidants

In this work, we have synthesized a series of 2-thiazolylhydrazone derivatives ( 1–27 ) and investigated their biological activities as tyrosinase inhibitors and antioxidants. Some compounds showed potent tyrosinase inhibitory activities and 4-(2-(2-(1-(4-Aminophenyl)ethylidene)-hydrazinyl)thiazol-4-yl) phenol ( 26 ) showed more potent inhibitory effect than the standard tyrosinase inhibitor kojic acid (IC₅₀: 9.8 μM vs. 23.6 μM). Compounds 2 , 14 , and 26 exhibited high antioxidant activities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. The structure–activity relationship (SAR) indicated that the substitutions of bromine, hydroxyl group, and amino groups cause great effect to the inhibition effect against tyrosinase. The mechanism and kinetic studies demonstrated that the inhibitory effect of compound 26 on the tyrosinase by acting as the reversible and uncompetitive inhibitor. Docking studies suggests that compound 26 interacts strongly with mushroom tyrosinase via hydrogen bonding.     

Thermo-oxidative reactions of crude oils

In this research, thermo-oxidative reactions of crude oils of different origin are determined in limestone matrix using simultaneous thermogravimetry and differential thermal analysis (TG–DTA) systems. Two different reaction regions were identified known as low temperature (LTO) and high temperature oxidation (HTO). Kinetic parameters of the samples were determined by four different methods and the results are discussed.     

Thiophosphate esters of cashew nutshell liquid derivatives as new antioxidants for poly(methyl methacrylate)

In this work, poly(methyl methacrylate) films 1% additivated with new thiophosphate esters antioxidants derived from technical Cashew Nutshell Liquid (CNSL), a byproduct of the cashew nut (Anacardium occidentale L.) industry, were investigated by thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) measurements under inert (N₂) and oxidative (synthetic air) atmospheres. Three new products were synthesized and characterized by GC/MS, ¹H and ³¹P NMR. The analyses were focused on the onset (T _e) and offset temperature (T _o) of degradation of the films, and on the maximum degradation temperature (T _MAX). It was observed that the thermal stability of the films increased with the addition of the thiophosphate ester antioxidants, which indicates that CNSL could be used as a natural source of phenolic material for the synthesis of antioxidants.     

Effect of chitosan derivatives as rubber antioxidants for increasing durability

A series of chitosan derivatives, namely polydiethylamino-ethylmethacrylate-chitosan-graft-copolymer (chitosan-g-DEAEMA), polycarboxy-chitosan-graft copolymer (chitosan-g-COOH), polyvinyl alcohol chitosan-graft-copolymer (chitosan-g-VOH), and carboxymethyl-chitosan (CM-chitosan), were synthesized and investigated as antioxidants for natural rubber (NR) and acrylonitrile butadiene rubber (NBR) mixes and vulcanizates to increase their durability. The rheometric characteristics of the rubber mixes were determined using an oscillating disc rheometer. The physico-mechanical properties of the rubber vulcanized were measured before and after exposure to thermal oxidative aging. It was found that the CM-chitosan had an accelerating effect on the curing process of NR and NBR. Also, the investigated polymers enhanced the properties of rubbers (NR and NBR) especially after ageing up to 7 days compared with commercial antioxidants, such as phenyl ß-naphthylamine (PßN) and N-isopropel-Nphenyl-p-phenylene diamine (IPPD) which are used in the rubber industry. After ageing, the retained values of tensile strength, modulus at 100 % strain, and elongation at break were improved. The optimum concentration of the investigated compounds used to give good properties was found to be 1–2 parts per 100 of rubber (phr). In addition, these prepared polymers showed a decrease in the equilibrium swelling of rubber in toluene which is the proper solvent and consequently increases the crosslink density for rubbers.     

有机铜作为润滑油高温抗氧剂的研究

在高档的润滑油中除了加有主抗氧剂ZnDTP外，还需加入其它助抗氧剂以弥补其高温抗氧性的不足。本研究合成了几种有机铜盐高温抗氧剂，用DTA法评价了它们及一些常用抗氧剂对润滑油的热稳定性的影响，发现铜铜盐的高温抗氧性能比一些常用抗氧剂好，可满足高档油的需求。     

Pyrocatechol and its derivatives as antioxidants and prooxidants

The effect of pyrocatechol and its derivatives (4,5-dichloro- and 4,5-dibromo pyrocatechols, veratrol, 4,5-dichloro- and 4,5-dibromoveratrol) on the free-radical oxidation of propan-2-ol in aqueous solutions, initiated by γ-radiation. Pyrocatechol and dihalocatechols exhibit antioxidant properties, whereas dihaloveratrols exhibit prooxidant properties. Dibromoveratrol showed more expressed prooxidant properties.     

Synthesis and biological evaluation of new ligustrazine derivatives as anti-tumor agents

To discover new anti-cancer agents with multi-effect and low toxicity, a series of ligustrazine derivatives were synthesized using several effective anti-tumor ingredients of Shiquandabu Wan as starting materials. Our idea was enlightened by the "combination principle" in drug discovery. The ligustrazine derivatives' anti-tumor activities were evaluated on the HCT-8, Bel-7402, BGC-823, A-549 and A2780 human cancer cell lines. In addition the angiogenesis activities were valued by the chick chorioallantoic membrane (CAM) assay. 1,7-bis(4-(3,5,6-Trimethylpyrazin-2-yl)-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (4) and 3 α,12 α-dihydroxy-5β-dholanic acid-3,5,6-trimethylpyrazin-2-methyl ester (5) not only displayed antiproliferative activities on these cancer cells, but also dramatically suppressed normal angiogenesis in CAM. The LD?? value of the compound 5 exceeded 3.0 g/kg by oral administration in mice.     

HPLC determination of PAHs in mineral oils used as dispersing agents for herbicides

Summary The representative refined mineral oil samples, crude petroleum straightrun distillates, potentially used in the manufacture of crop protection products were analysed by isocratic and gradient high performance liquid chromatography (HPLC) to investigate their trace polycyclic aromatic hydrocarbon (PAH) content. Liquid-liquid extraction followed by size-exclusion column chromatography was employed to isolate the fraction containing PAHs with more than two fused rings. The identity of individual PAHs was confirmed by comparing their UV and fluorimetric detector signals with those recorded from reference standards. The level of extracted PAHs in the oil samples are discussed with respect to their physical and chemical properties.     

l-Isofucoselenofagomine and derivatives: dual activities as antioxidants and as glycosidase inhibitors

The synthesis of a series of l-fuco-configured selenosugars, isosters of the potent glycosidase inhibitor isofucofagomine has been accomplished by a double nucleophilic displacement of a dimesylated derivative with selenide anion generated in situ. Se-Alkylation and oxidation of the corresponding selenane afforded a selenonium and a selenoxide, respectively. The biological activities of such compounds have been evaluated, finding a dual activity caused by the presence of the selenium atom: the selenane exerted a good glutathione peroxidase mimicry by efficiently scavenging H₂O₂ in the presence of thiols, whereas the stable selenoxide derivative was found to be the first example of a selenosugar acting as a good α-l-fucosidase inhibitor.     

Synthesis and in vitro evaluation of new benzothiazole derivatives as schistosomicidal agents

A series of benzothiazol-2-yl-dithiocarbamates 3a-d along with their copper complexes 4a-c were synthesized via the reaction of suitable alkyl, aralkyl or heteroaryl halides with the sodium salt of benzothiazol-2-yl-dithiocarbamic acid, followed by complexation with copper sulphate. N-(4-Acetyl-5-aryl-4,5-dihydro-1,3,4-thiadiazol-2-yl)-N-benzothiazol-2-yl-acetamides 7a-c were synthesized by cyclization of the appropriate thiosemicarbazones 6a-c in acetic anhydride. Selected compounds were screened for in vitro schistosomicidal activity against Schistosoma mansoni at three different dosage levels (10, 50 and 100 microg/mL). Three of these products, 4a-c, showed schistosomicidal activity similar to praziquantel, with 100% worm mortality at 10 microg/mL. These compounds would constitute a new class of potent schistosomicidal agents.     

3,5-Di-tert-butyl-4-hydroxybenzaldehyde derivatives as antioxidants in cumene oxidation

A series of 4-hydroxy-3,5-di-tert-butylbenzaldehyde derivatives were prepared, and their antioxidant properties were studied.     

Synthesis and biological evaluation of new oxime-ether derivatives of steroid as anti-bacterial agents

Various oxime-ether derivatives of cholesterol have been synthesized by the alkylation of the steroidal oxime with 1-(2-chloroethyl) pyrrolidine hydrogen chloride/chloroethylamine hydrochloride in the presence of sodium methoxide in dry methanol. The structures of these compounds were elucidated by IR ¹H NMR, FAB mass spectroscopic methods and elemental analyses. The anti-bacterial activity was first tested in vitro by the disk diffusion method against two Gram-positive and two Gram-negative bacteria, and then the minimum inhibitory concentration (MIC) of compounds were determined. The results showed that the chloro derivatives exhibited better anti-bacterial activity than the standard drug chloramphenicol.     

Ultrasound-assisted synthesis and anticancer evaluation of new pyrazole derivatives as cell cycle inhibitors

We designed new pyrazole derivatives as inhibitors of the cell cycle kinases and developed a simple environmentally sustainable synthesis process. We synthesized the pyrazolyl thiourea derivatives using rapid ultrasound mediated methods and confirmed their structures by NMR and IR spectra. The apoptosis and necrosis inducing effects of the new compounds were investigated. Cell cycle analysis and expression of genes involved in apoptosis, cell cycle and xenobiotic metabolism were studied. The compounds presented modest apoptotic effects in human cancer cells. The N-[[3-(4-bromophenyl)-1H-pyrazol-5-yl]carbamothioyl]-4-chloro-benzamide compound (4e) induced a significant increase of cells in G2/M phases in conjunction with an increased expression of cyclin A and cyclin B, emerging as a promising anticancer drug, to be further developed in animal models of cancer.     

Pyran derivatives as new perfumes

2-Nonyl acetate, 2-hexyltetrahydrofuran, 4-heptyl-1,3-dioxane, 3-hexyl-4-hydroxytetrahydropyran and its acetate, and decane-1,3-diol and its diacetate were isolated from the products of the reaction of 1-nonene with formaldehyde in acetic and sulfuric acids. The structures of the substances isolated were confirmed by the results of functional analysis and by IR and PMR spectroscopy. The stereoisomeric composition of 3-hexyl-4-hydroxytetrahydropyran and its acetate was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1447–1450, November, 1971.     

Synthesis and in vitro evaluation of new diphenyl ether derivatives as serotonin transporter ligands

For the development of new ligands as potential imaging agents for the serotonin transporter (SERT),a series of diphenyl ether derivatives have been synthesized,characterized,and evaluated for their in vitro binding affinities to the SERT. Among the above compounds,2-(2-((dimethylamino)methyl)-4-fluoro-phenoxy)-5-bromobenzenamine (15) and 2-(2-((dimethylamino)methyl)-4-fluorophenoxy)-5-iodobenzene amine (16) show high binding affinities for the SERT with Ki values of 0.28 and 0.20 nmol·L-1,respectively. They can be further labeled with carbon-11,fluorine-18,iodine-123 or bromine-76,and evaluated as useful imaging agents for the SERT. Moreover,the study of the structure-activity relationship (SAR) provides some useful information for the future design of new ligands.     

Synthesis and evaluation of new pyrazoline‐thiazole derivatives as monoamine oxidase inhibitors

A novel series of 1,3,5‐trisubstituted‐2‐pyrazoline derivatives ( 4a ‐ 4k ) was synthesized and their chemical structures characterized by ¹H NMR, ¹³C NMR, and mass spectroscopy. These compounds were evaluated as inhibitors for of type A and type B monoamine oxidase (MAO) enzymes. The most common inhibitors of MAO enzymes used to treat depression and anxiety such as selegiline and moclobemide drugs were used as reference agents. A result of biological evaluation of these compounds revealed compounds 4c , 4d , and 4? as potent and selective MAO A inhibitors. The most active compound 4? , which is 2,4‐dimethoxy at phenyl ring, showed strong inhibitory activity at MAO A (IC₅₀ of 0.0445 ± 0.0018μM). Furthermore, compounds 4c and 4d showed significant inhibition profile on MAO A with the IC₅₀ values 0.1423 ± 0.0051μM and 0.2148 ± 0.0067μM, respectively.     

Evaluation of some derivatives of 4-quinazolones as antioxidants and antirads in rubber

Derivatives of 4-quinazolones were compounded with rubber. The relation between their efficiencies as antioxidants and antirads was studied. It was found that their efficiencies as antioxidants and antirads fall in the same order but differ in degree.