The tyrosinase enzyme plays an essential role in the pigmentation of human skin, fruits, and vegetables. It has been tied with several human skin diseases and post-harvest problems. Hence, the ...tyrosinase enzyme becomes an excellent therapeutic target to overcome these issues. This study aimed to screen tyrosinase inhibitors by synthesizing halogen-substituted pyrazolopyridine derivatives. The pyrazolopyridine compound was obtained through two stages of synthesis. First, the intermediate compound, a derivative of 3,5-bis(arylidene)-4-piperidone, was synthesized through the Cleisen-Schmidt condensation reaction of 4-piperidone and benzaldehyde derivatives. Furthermore, the intermediate compound was reacted with phenylhydrazine through a cyclocondensation reaction to produce the titled compound with an 11% yield. The chemical structure of the target compound was identified through the interpretation of UV, FTIR, NMR, and HRMS spectra. Then an in vitro assay was conducted on the tyrosinase enzyme of the fungus Agaricus bisporus by detecting the presence of dopachrome at a wavelength of 492 nm. As a result, the in vitro assay showed that the titled compound had a weak inhibitory activity, and the IC50 value was > 500 µM. Thus, the synthesized compound is considered inactive.
New pyridine based ruthenium complexes with different substituents were synthesized and characterized by Uv-Visible, fluorescence, FTIR and NMR spectroscopies. The substituents and solvent effects of ...the synthesized compounds on photoluminescence properties have been investigated. The compounds exhibit solvatochromic effect in different solvents. The electrochemical studies of the compounds were performed by cyclic voltammetry. The HOMO and LUMO energy levels are in the range (-5.51)-(-5.52) eV and (-3.04)-(-3.07) eV, respectively. These results indicate that there is no an important effect of side groups on electrochemical properties.
Farklı sübstitüentlere sahip yeni piridin esaslı rutenyum kompleksleri sentezlendi ve Uv-Visible, floresans, FTIR ve NMR spektroskopileri ile karakterize edildi. Sentezlenen bileşiklerin fotolüminesans özellikleri üzerine sübsitüentler ve çözücü etkileri araştırılmıştır. Bileşikler farklı çözücüler içerisinde solvakromatik etki göstermektedir. Bileşiklerin elektrokimyasal çalışmaları döngüsel voltammetri ile gerçekleştirildi. HOMO ve LUMO enerji seviyeleri sırasıyla (-5.51)-(-5.52) eV ve (-3.04-(-3.07) eV aralığındadır. Bu sonuçlar yan grupların elektrokimyasal özellikleri üzerine önemli bir etkisinin olmadığını göstermektedir.
Hekzakarbonilmetal(0); M:Cr, Mo, W, bileşikleri ile sübstitüye piridin (tert-bütilpiridin) arasında, 10 ºC de yapılan fotokimyasal tepkimeler, cis-tetrakarbonil(tert-bütilpiridin)metal(0) ...bileşiklerini oluşturmaktadır. Sentezlenen bu organometalik bileşikler yüksek vakum kullanılarak yeniden kristallendirme yöntemi ile saflaştırılır ve yapıları FTIR-, 1H- ve 13C-NMR spektroskopileriyle incelenir. Spektroskopik incelemeler sonucunda elde edilen veriler piridin ligand halkasının sp2 hibritli azotundan zayıf şekilde bağladığını ortaya koymaktadır. Ayrıca, piridin halkasının 4-konumu üzerindeki sübstitüentinin boyutunun, piridin ile merkezi atomun koordinasyonunu engellemediği gösterilmiştir.
Telah dilakukan sintesis kemosensor anion senyawa 4-(2,6-difenil-piridin-4-il)-2-metoksi-fenol (DPMF). Sintesis senyawa target DPMF dilakukan melalui senyawa antara kalkon dengan rendemen reaksi 77%. ...Uji sebagai sensor anion dilakukan dalam pelarut DMSO-air terhadap anion F-, Cl-, Br-, CN- dan H2PO4-. Senyawa DPMF ini menghasilkan perubahan warna dari tidak berwarna menjadi kuning pada penambahan anion CN-. Analisis spektrofotometer UV-vis pada senyawa DPMF menghasilkan perubahan λmak = 320 nm ke λmak = 370 nm pada penambahan anion CN-. Limit deteksi terhadap anion CN- sebesar 4,11x10-6M. Senyawa ini juga dapat berperan sebagai kemosensor fluoresen dengan sistem “ON-OFF”.
Telah dilakukan penelitian tentang Karakterisasi Katalis Pt-Pd/Zeolit Alam Regenerasi pada Reaksi Hidrodenitrogenasi Piridin. Tujuan dari penelitian ini adalah untuk mempelajari karakter katalis ...Pt-Pd/zeolit alam baru, bekas dan hasil regenerasi pada hidrodenitrogenisasi piridin. Katalis Pt-Pd/zeolit alam terdeaktivasi diregenerasi dengan cara dioksidasi dengan gas O2 pada temperatur 350oC selama 2 jam, dan direduksi dengan gas H2 pada temperatur 400oC selama 1 jam. Karakterisasi katalis baru (fresh), terdeaktivasi dan terregenerasi meliputi penentuan luas permukaan, volume pori dan rerata jejari pori dengan alat Gas Sorption Analyzer NOVA-1000 berdasarkan adsorpsi gas N2 serta penentuan keasaman dengan metode adsorpsi gas amoniak. Hasil penelitian menunjukkan bahwa deaktivasi katalis menyebabkan penurunan luas permukaan spesifik, volume total pori dan keasaman katalis, sedangkan proses regenerasi pada katalis bekas dengan metode oksidasi dan reduksi meningkatkan luas permukaan spesifik, volume total pori, rerata jejari pori dan keasaman katalis.
Condensation of β-amino-α,γ-dicyanocrotononitrile (1) with acetophenone gave 2-amino-4-phenylpenta-1,3-diene-1,1,3-tricarbonitrile (2). The latter product was used in a series of heterocyclization ...reactions with different reagents such as diazonium salts, hydrazines, hydroxylamines and elemental sulfur to give pyridazine, pyrazole, isoxazole and thiophene derivatives, respectively. On the other hand, it gave pyridine derivatives with aromatic aldehydes folowed by reaction with cyanomethylene reagents. The MIC values for the newly synthesized product were measured against E. coli, B. cereus, B. subtilis and C. albicans.
Kondenzacijom β-amino-α,γ-dicijanokrotononitrila 1 s acetofenonom dobiven je 2-amino-4-fenilpenta-1,3-dien-1,1,3-trikarbonitril (2) koji je upotrebljen u reakcijama heterociklizacije s različitim reagensima poput diazonijevih soli, hidrazina, hidroksilamina i elementarnog sumpora pri čemu su nastali derivati piridazina, pirazola, izoksazola, odnosno tiofena. Spoj 2 je u reakciji s aromatskim aldehidima te naknadno sa cijanometilenima dao derivate piridina. Određene su MIC vrijednosti za novosintetizirane spojeve protiv E. coli, B. cereus, B. subtilis i C. albicans.
In this study, characterization and surface acidity of Siral ($SiO_2-Al_2O_3$) compounds were investigated with Hammett acidity functions, the n-butylamine titration method and FTIR analysis of the ...spectra of pyridine adsorption. All the samples had an acid strength of $H_o\leq\le$+2.8. The calculated total amount of acid of the samples increased with the increase in $SiO_2$ content up to Siral 40 and then decreased sharply in the case of Siral 80. Maximum amount of acidity was observed in the case of Siral 40 as 1.37mmole/g. No evidence was found for a band at 1540 $cm^{-1}$ on Pural indicating that there were no Bronsted sites on the surface strong enough to react with pyridine. As a result, we can say that the Lewis sites predominate in all the silica-aluminas.
This study provides a new approach for the synthesis of pyridine and benzene templated potential peptidomimetics. By the attachment of various amino acid side chains in different combinations on the ...pyridine template at the 2- and 3- positions and on the benzene core at 1,2,4 positions, different peptidomimetics may be obtained. Arg-10, Leu-11 and Tyr-13 amino acid side chain mimics and their precursors were attached to the pyridine and benzene core with a special arrangement to produce potential peptidomimetics of omega-conotoxin MVIIA.
Systems formed by the pyrene derivatives 3-hydroxypyrene and 1-aminopyrene with pyridine were studied. The thermodynamic and kinetic parameters of the systems were calculated using the changes in the ...absorption and emission spectra which occur due to hydrogen bond or complex formation.The decrease of the formation rate constant in the series methylcyclohexane, benzene, and o-chlorotoluene may be due to a more difficult formation of the hydrogen bond complex due to the increase of the dielectric constant in the solvent series.
The adsorption behaviour of poly(4 - vinyl pyridine) towards copper (II) ion in aqueous solutions was studied by a batch equilibriation technique. Influence of treatment lime, pH of the solution and ...metal ion concentration on the adsorption were investigated. 45 minutes of adsorption time was found sufficient to reach adsorption equilibrum for the copper (II) ion. The optimum pH was found to be 4,5. The adsorption saturation value was reached at 1,27 mmol ions per gram poly(4 - vinyl pyridine) against 3.15 mM copper (II) ions. It was observed that the adsorption isotherm of Cu (II) fits Freundlich - type isotherms.
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