Devarayan Kesavan

Physicochemical studies of glucose, gellan gum, and hydroxypropyl cellulose--inhibition of cast iron corrosion.

Glucose, gellan gum, and hydroxypropyl cellulose were studied against the acid corrosion of cast iron by means of weight loss, potentiodynamic polarization, and AC impedance spectroscopy techniques. The inhibition efficiency was found to increase with increasing concentration of the inhibitors. The effect of immersion time and temperature were also studied. The addition of potassium iodide to the corrosion-inhibition system showed both antagonism and synergism toward inhibition efficiency. Polarization studies revealed the mixed-type inhibiting nature of the carbohydrates. The adsorption of inhibitors on the cast iron surface obeys Langmuir adsorption isotherm model, both in presence and absence of KI. Physical interaction between the inhibitor molecules and the iron surface was suggested by the thermochemical parameters, rather than chemical interaction.

Synthesis of novel photosensitive polymers for the protection of mild steel from acid corrosion

Novel photosensitive polymers, namely poly((E)-(1-(10-(4-(3-(biphenyl-4-yl)-3-oxoprop-1-enyl)phenoxy)pentyl)-1H-1,2,3-triazol-4-yl)methyl propionate) (BI-5), poly((E)-(1-(10-(4-(3-(biphenyl-4-yl)-3-oxoprop-1-enyl)phenoxy)hexyl)-1H-1,2,3-triazol-4-yl)methyl propionate) (BI-6) and poly((E)-(1-(10-(4-(3-(biphenyl-4-yl)-3-oxoprop-1-enyl)phenoxy)decyl)-1H-1,2,3-triazol-4-yl)methyl propionate) (BI-10), were synthesized and the structure of the products were confirmed by 1H NMR, FT-IR and UV-Visible spectral analysis. The rate of photo-cross-linking was evaluated by UV-Visible spectroscopic technique and the results revealed the efficient cross linking behavior of the synthesized polymers. For the first time in literature, these photo-cross-linkable polymers were investigated as inhibitors against the corrosion of mild steel (MS) in 1.0 M hydrochloric acid solution (HCl) by means of Tafel polarization and electrochemical impedance measurements. The polymers showed higher activity even at very lower concentrations (5 to 15 ppm). Potentiodynamic polarization studies revealed the mixed-type inhibiting nature of the inhibitors. The adsorption of inhibitors on the MS surface obeys the Langmuir adsorption isotherm model. The standard free energy of adsorption (ΔGads) value confirmed that physisorption as well as chemisorption takes place on the MS surface. The protection of MS by inhibitors was further well supported by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) analysis.

An anti-inflammatory and anti-microbial flavone glycoside from flowers of Cleome viscosa.

Background Natural products isolated from plant sources have been demonstrated as potential candidates against several ailments. The scientific investigations on the underlying principles of phytotherapy can pave way for the convergence of traditional medicines and modern science and technologies. Results Quercetin 3-O-(2′′-acetyl)-glucoside obtained from ethyl acetate fraction of Cleome viscosa is studied against inflammatory of carrageenan-induced rat paw edema ( in vivo) and microbial activity on ( in vitro). The structure of the glycoside is confirmed by means of hydrogen-1 nuclear magnetic resonance spectroscopy, carbon nuclear magnetic resonance spectroscopy, attached proton test, and mass spectrum. The flavonoid glycoside showed significant anti-inflammatory activity of on carrageenan-induced rat paw edema ( in vivo) and anti-microbial activity ( in vitro) on Staphylococcus aureus (gram positive) and Escherichia coli (gram negative). The anti-inflammatory effect of the flavonoid glycoside may be due to the inhibition of prostaglandin synthesis. Selective toxicity with flavonoid glycoside towards the gram-positive bacteria was found on S. aureus. Conclusions The present study reveals the anti-inflammatory and antimicrobial activities of an isolated quercetin 3-O-(2′′-acetyl)-glucoside from a natural source ( C. viscosa).

Antibacterial Activities of 4-Substituted-2-[(E)-{(1S,2R)/(1R,2S)-1-Hydroxy-1-Phenylpropan-2-Ylimino}Methyl]Phenol

A series of norephedrine‐based Schiff bases (1a–6a and 1b–6b) were synthesized by reacting substituted salicylaldehydes with d‐norephedrine or l‐norephedrine. The structure of these compounds was confirmed by elemental analyses and spectroscopic techniques. The molecular structures of 5a and 6a have been determined by X‐ray crystallography, which revealed that the compounds are in the oxoamino form, with bent intramolecular N‐H···O (N···O ≈ 2.58 Å) hydrogen bonds and that they are associated in dimers bridged by linear intermolecular O‐H···O (O···O ≈ 2.69 Å) hydrogen bonds. The density functional theory calculations on 5a confirmed that the oxoamino form is more stable than the phenolimino form by 12.2 kcal/mol. All the compounds were evaluated for their antibacterial activity using resazurin dye as indicator by twofold dilution method against four bacteria namely, Bacillus subtilis (NCIM2718), Staphylococcus aureus (NCIM5021), Escherichia coli (NCIM2931), and Proteus vulgaris (NCIM2813).

Studies On The Inhibitive Effect Of 3-Hydroxyflavone On The Acid Corrosion Of Mild Steel

The corrosion inhibition effect of 3-hydroxyflavone was studied on mild steel in 1 M hydrochloric acid (HCl). The anticorrosive effect was evaluated by weight loss and electrochemical methods which include Tafel polarization and AC impedance studies at 300 K. In weight loss method, the inhibition efficiency increased with increase in inhibitor concentration, and decreased with increase in temperature and immersion time, and acid concentration. The inhibitor showed maximum efficiency of 91% at 4 × 10-4 M concentration in 1 M hydrochloric acid. The Tafel polarization study showed that the inhibitor behaves likely as cathodic type. The corrosion inhibition effect measured by weight loss method and electrochemical studies was in good agreement with each other. The surface analysis was done by using scanning electron microscope (SEM). Several adsorption isotherms are assessed to study the adsorption behavior of the inhibitor on the mild steel surface. The negative value of ΔGads indicates the spontaneous adsorption of the inhibitor on mild steel surface.

A new biflavone glycoside from flowers of Asystasia gangetica

The yellow parts of the flowers of Asystasia gangetica were extracted with 85% methanol under reflux. The alcoholic extract was concentrated in vacuo and the aqueous extract was fractionated with solvents of increasing polarity. The ethyl acetate fraction yielded a yellow solid, which was characterized as apigenin 7-O-glucosyl(3′ → 6″)luteolin 7″-O-glucoside using UV, 1H, 1H–1H COSY, 13C NMR, and mass spectral studies.