Spectrophotometric investigation of protolytic equilibria of rutin

The dissociation constants of rutin in aqueous-methanol medium (6040 v/v), the values of which are pK₁=–2.92±0.06, pK₂=6.72±0.11, pK₃=8.26±0.05, pK₄=12.57±0.09, were estimated by using the spectrophotometric method. They were ascribed to the dissociation of protonated oxygen atom at position 1 and then to hydroxyl groups at positions 7, 4', 5, respectively. Resonance structures of H₃L^– ion of rutin were suggested and, by using them, the greater dissociability of the hydroxyl group at position 7 in relation to the –OH group at position 4' was explained.     

Synthesis and characterization of bis(2-aminophenyl)disulphide diimine derivatives and their ruthenium complexes

Condensation of bis(2-aminophenyl)disulphide with aromatic aldehydes yielded the corresponding dithiophenyldiimines. Dinuclear ruthenium complexes were obtained by reacting the diimines (3) [bis(3-nitrobenzaldehyde)-phenyldisulphide diimine], (5) [bis(2-chlorobenzaldehyde)-phenyldisulphide diimine], (8) [bis(2-methoxybenzaldehyde)-phenyldisulphide diimine] and (9) [bis(2-hydroxybenzaldehyde)-phenyldisulphide diimine], with RuCl₃ in the presence of L (L=2,2-bipyridine, 1,10-phenanthroline, 3,4-diaminotoluene, pyridine and PPh₃) in EtOH. The two metal centres, connected through bridging chlorides, are in octahedral environments with one metal centre coordinated to sulphur and water while the other is coordinated to L.     

ICP-MS determination of toxic-metal release from pumping systems for food processing

The release of heavy metals from uncovered and nickel-covered brass pumps has been evaluated by ICP-MS analysis in both simple ultrapure water and 3% acetic acid solution (mimic of neutral and acid edible liquids, respectively), following a procedure similar to that recommended by the National Sanitation Foundation (NSF) International, Test Procedure P203. The results found highlight that the main release regards zinc, copper and lead, i.e. the three major metals present in brass alloys. The first contact of brass surfaces with the extraction solvent leads to an extensive Pb release which is comparable with that observed for Cu and Zn. Subsequent washings reduce markedly the Pb release, thus rising in evidence a progressive surface passivation. In particular, the Pb release found after four repeated washings turns out to approach the limit set by both Italian and USA governments for liquids used for food purposes when determined in neutral media, while it remains quite higher when evaluated in acid media. Release analyses conducted on nickel-covered brass pumps point out that the Niploy nickel coating process is very effective for brass surface protection, in that the Pb release is reduced of about three orders of magnitude, but a Ni release exceeding the relevant permitted level is in this case observed.     

Spectroscopic and thermodynamic characterization of the E151D and E151A altered leucine aminopeptidases from Aeromonas proteolytica

Previous kinetic characterization of the glutamate 151 (E151)-substituted forms of the leucine aminopeptidase from Aeromonas proteolytica (Vibrio proteolyticus; AAP) has provided critical evidence that this residue functions as the general acid/base. The close proximity of similar glutamate residues to the bridging water/hydroxide of the dinuclear active sites of metalloenzymes (2.80 and 3.94 angstroms in carboxypeptidase G2 and 3.30 and 3.63 angstroms in AAP), suggests it may also be involved in stabilizing the active-site metal ions. Therefore, the structural perturbations of the dinuclear active site of AAP were examined for two E151-substituted forms, namely E151D-AAP and E151A-AAP, by UV-vis and electron paramagnetic resonance (EPR) spectroscopy. UV-vis spectroscopy of Co(II)-substituted E151A-AAP did not reveal any significant changes in the electronic absorption spectra. However UV-vis spectra of mono- and dicobalt(II) E151D-AAP exhibited a lower molecular absorptivity compared to AAP (23 and 43 M(-1) cm(-1) vs. 56 and 109 M(-1) cm(-1) for E151D-AAP and AAP, respectively) suggesting both Co(II) ions reside in distorted octahedral coordination geometry in E151D-AAP. EPR spectra of [Co_(E151D-AAP)], [ZnCo(E151D-AAP)], and [(CoCo(E151D-AAP)] were identical, with g(perpendicular) = 2.35, g(parallel) = 2.19, and E/D = 0.19, similar to [CoCo(AAP)]. On the other hand, the EPR spectrum of [Co_(E151A-AAP)] was best simulated assuming the presence of two species with (i) g(x,y) = 2.509, g(z) = 2.19, E/D = 0.19, A = 0.0069 cm(-1) and (ii) g(x,y) = 2.565, g(z) = 2.19, E/D = 0.20, A = 0.0082 cm(-1) indicative of a five- or six-coordinate species. Isothermal titration calorimetry experiments revealed a large decrease in Zn(II) affinities, with K(d) values elevated by factors of approximately 850 and approximately 24,000 for the first metal binding events of E151D- and E151A-AAP, respectively. The combination of these data indicates that E151 serves to stabilize the dinuclear active site of AAP.     

Detection of methyl salicylate using polymer-filled chemicapacitors

Methyl salicylate (MeS) is used as a chemical warfare agent simulant to test chemical protective garments and other individual personal protective gear. The accurate and real-time detection of this analyte is advantageous for various testing regimes. This paper reports the results of MeS vapor exposures on polymer-filled capacitance-based sensors at temperatures ranging from 15 °C to 50 °C under dry and humid conditions. Multiple capacitors were arranged in an array on a silicon chip each having a different sorptive polymer. The sensors used parallel-plate electrode geometry to measure the dielectric permittivity changes of each polymer when exposed to water and MeS vapor. Of the four polymers tested against MeS, the optimal polymer displayed near or sub-parts-per-million detection limits at 35 °C (0–80%RH).     

Inhibition effect of phenyl compounds from the Oryza sativa roots on melanin production in murine B16-F10 melanoma cells

Five phenyl compounds, vanillin (1), methyl trans-ferulate (2), trans-p-coumaric acid methyl ester (3), N-benzoyltryptamine (4), and N-(trans-cinnamoyl)tryptamine (5), were isolated from the roots of Oryza sativa L. and identified on the basis of spectroscopic data. Compounds 3 and 5 showed strong inhibition effect on melanin production in murine B16-F10 melanoma cells and tyrosinase activity. Also, the quantitative analysis of the compounds was carried out using LC/MS/MS experiment. Compounds 3 and 5 could be used as skin-whitening agents.     

Microwave-assisted synthesis of triazole derivatives conjugated with piperidine as new anti-enzymatic agents

The current study was aimed for the study of piperidine-based triazole compounds for their biological potential against various enzymes. A novel library of compounds, 9a-r , having piperidine, 1,2,4-triazole, and propanamides was synthesized through consecutive steps including the formation of sulfonamide, hydrazide, 1,2,4-triazole, and thio-ether. Initially, 4-methoxybenzenesulfonyl chloride ( 1 ) and ethyl isonipecotate ( 2 ) were utilized to develop ethyl 1-(4-methoxyphenylsulfonyl)-4-piperidinecarboxylate ( 3 ). The product 3 was converted into respective hydrazide ( 4 ) which was further cyclized into 1,2,4-triazole ( 5 ) nucleus. A series of propanamides, 8a-r , were synthesized from different amines, 6a-r . These electrophiles, 8a-r , were reacted with compound 5 under conventional and microwave-assisted protocols to acquire the library of hybrids, 9a-r . The structural confirmations were availed by ¹H-NMR, ¹³C-NMR, and IR techniques. The whole series was evaluated for biological potential against acetylcholinesterase (AChE) and α-glucosidase enzymes. The biological evaluation ranges low to high in potential for different compounds based on the structural variations of synthesized compounds. Almost all the compounds remained active against both the enzymes except a few ones. The bovine serum albumin (BSA) binding study demonstrated the flow of drug in the body, and the docking study explained the interactions responsible for active behavior of synthesized compounds.