K. M. Lokanatha Rai

Photocatalytic degradation of rhodamine B dye using hydrothermally synthesized ZnO

The sunlight mediated photocatalytic degradation of rhodamine B (RB) dye was studied using hydrothermally prepared ZnO (T = 150°C andP ∼ 20–30 bars). Zinc chloride was used as the starting material along with sodium hydroxide as a solvent in the hydrothermal synthesis of ZnO. Different durations were tried to obtain pure ZnO phase, which was later confirmed through powder X-ray diffraction. The photocatalytic behaviour of the prepared ZnO was tested through the degradation of RB. The disappearance of organic molecules follows first-order kinetics. The effect of various parameters such as initial dye concentration, catalyst loading, pH of the medium, temperature of the dye solution, on the photo degradation of RB were investigated. The thermodynamic parameters of the photodegradation of RB, like energy of activation, enthalpy of activation, entropy of activation and free energy of activation revealed the efficiency of the process. An actual textile effluent containing RB as a major constituent along with other dyes and dyeing auxiliaries was treated using hydrothermally synthesized ZnO and the reduction in the chemical oxygen demand (COD) of the treated effluent revealed a complete destruction of the organic molecules along with colour removal.

Synthesis and pharmacological evaluation of 1,3,4-oxadiazole bearing bis(heterocycle) derivatives as anti-inflammatory and analgesic agents.

A series of novel ether-linked bis(heterocycle)s have been synthesized via [3+2]-cycloaddition reaction of nitrile oxide with allyl alcohol followed by intramolecular 1,3-diploar cycloaddition reaction of nitrile imine with carbonyl group. All the newly synthesized compounds were screened for their anti-inflammatory and analgesic activities. Among the list of compounds (7a-k) studied, 7d, 7g, 7j, and 7k exhibited excellent activity comparable to ibuprofen and aspirin at the similar dosages.

Synthesis and evaluation of antioxidant and antibacterial activities of new substituted bis(1,3,4-oxadiazoles), 3,5-bis(substituted) pyrazoles and isoxazoles.

Two series of five membered heterocyclic bis(1,3,4-oxadiazole) derivatives 2(a-h) and 3,5-bis(substituted)pyrazoles, isoxazoles 3(a,b,d-i), 4(a-c) were synthesized via oxidative cyclization of some diaroylhydrazones using chloramine-T and cyclocondensation reaction with hydrazine hydrate and hydroxylamine hydrochloride, respectively. The newly synthesized compounds were screened for antioxidant and anti-microbial activities. Compounds 2(b), 3(b), and 4(a) showed higher antioxidant activity at 10 μg/ml while compounds 2(a), 3(a), 3(f), and 4(a) exhibited better anti-microbial activity at 100μg/ml compared with standard vitamin C and ciprofloxacin, respectively. Structures of newly synthesized compounds were confirmed by elemental analysis and spectral IR, (1)H NMR, and (13)C NMR data.

Synthesis and evaluation of antimitotic activity of alkylated 2-amino-1,3,4-oxadiazole derivatives

Series of N-alkylated-2-amino-1,3,4-oxadiazoles (2) were synthesized via alkylation of 2-amino-1,3,4-oxadiazoles (1) under phase transfer condition. This paper also describes the study of antimitotic activity of these molecules by onion root tip method.

Synthesis of novel 3-[5-ethyl-2-(2-phenoxy-ethyl)-pyridin]-5-substituted isoxazoline libraries via 1,3-dipolar cycloaddition and evaluation of antimicrobial activities

A series of novel 3-[5-ethyl-2-(2-phenoxy-ethyl)-pyridin]-5-substituted isoxazolines were synthesized via 1,3-dipolar cycloaddition of in situ generated nitrile oxide from 4-[2-(5-ethylpyridyl)-ethoxy]-benzaldoxime with alkenes to obtain new heterocyclic libraries containing a pyridine moiety in addition to the isoxazoline ring. The newly synthesized compounds were screened for their antimicrobial activity and were compared with standard drugs. The compounds demonstrated potent to weak antimicrobial activity. Of the compounds studied, compounds 3c and 3f showed significant antibacterial as well as antifungal activity. Compounds 3e and 3g showed moderate activity. The title compounds represent a novel class of potent antimicrobial agents.

Chlorahine-T in Heterocyclic Synthesis;1 a Simple Procedure for the Genedation of Nitrilihines and its Application to the Synthesis of Pyrazolines

Abstract A new method of generating nitrilimines is described. It involves the reaction of aromatic as well as aliphatic aldehyde hydrazones with chloramine-T. In the presence of olefins pyrazolines are obtained in good yield.

Intermolecular 1,3-Dipolar Cycloadditions of Preformed Nitrile Oxides with Phenyl Vinyl Sulphone1

Abstract Dipolar cycloadditions of nitrile oxides 2, isolated from the oxidative dehydrogenation of aldoximes by chloramine-T, with vinyl sulphone 3 are discussed.

TRANSFORMATION OF 1,3,4-OXADIAZOLES TO 1,3,4- THIADIAZOLES USING THIOUREA.+

A new and convenient procedure for the direct conversion of 1,3,4-oxadiazoles to 1,3,4-thiadiazole using thiourea as thionating agent is described.

Synthesis, characterization, antidepressant and antioxidant activity of novel piperamides bearing piperidine and piperazine analogues.

A series of piperamide derivatives (8a-j) was synthesized with various substituted piperidine and piperazine compounds. The prepared compounds were evaluated for antibacterial activity against gram-positive and gram-negative bacteria and antifungal activity by disc diffusion method. The antioxidant activity of the compounds was evaluated by DPPH and superoxide radical scavenging method and antidepressant activity using forced swim and tail suspension behavioral despair tests in mice. The compounds 8a, 8b and 8c were investigated for their monoamine oxidase A and B (MAO-A and MAO-B) inhibitory property. Some of the test compounds were active in forced swim test (FST) and tail suspension test (TST). Compounds 8a and 8b showed a significant effect, when compared to standard drug, clorgyline.

Herbal remedies for the management of seed-borne fungal pathogens by an edible plant Decalepis hamiltonii (Wight & Arn)

Abstract Antifungal activity-guided assay of solvent extracts of Decalepis hamiltonii (Wight & Arn) (Asclepiadaceae) against important phytopathogenic fungi, known to cause diseases in sorghum, maize and paddy proved to be highly significant. Among the five solvent extracts tested, Petroleum ether extract showed highly significant antifungal activity. Phytochemical analysis revealed that the antifungal active principle is a phenolic compound. TLC separation of the phenolic fraction using chloroform as an eluting solvent revealed the presence of seven bands but the antifungal activity was observed only in band five with Rf value 0.77. The antifungal active compound is identified as 2-hydroxy-4-methoxybenzaldehyde based on Nuclear Magnetic Resonance (NMR) and mass spectral analysis. The Minimal inhibitory concentration (MIC) varied between 200 μg ml−1 and 700 μg ml−1 depending on the fungal species. Seed treatment of the active principle significantly increased seed germination and seed vigour with a corresponding decrease in seed mycoflora. The antifungal active compound was effective against all the 24 fungal species tested suggesting broad-spectrum antifungal activity. Comparative evaluation of the active principle with the synthetic fungicides revealed that the antifungal activity of the active principle obtained from the plant is better than that of synthetic fungicide. This plant being an edible one can be exploited in the management of seed-borne pathogenic fungi and the prevention of biodeterioration of grains and mycotoxin elaboration during storage.