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ABSTRACT:
A Series of 2-((naphthalen-1-yl) methyl)-5-substituted-1,3,4-oxadiazole derivatives were synthesized by refluxing naphthyl acetic acid hydrazide with substituted aromatic acids in presence of phosphorous oxychloride. The intermediate naphthyl acetic acid hydrazide (2) was prepared by treatment of naphthyl acetic acid ester (1) with hydrazine hydrate. The chemical structures of all the twelve synthesized compounds were confirmed by means of IR, 1H NMR and Mass spectral data. All the title compounds were screened for antioxidant activity by Nitric oxide scavenging activity, reduction of DPPH and antibacterial activity using Cup plate method. Among the series of the compounds 4-hydroxy-3,5-dimethoxy (3k), 3-pyridyl (3h), 4-pyridyl (3i) derivatives showed good antioxidant activity in two invitro models. 4-chloro (3b) 4-hydroxy-3,5-dimethoxyderivative(3k), 4-pyridyl (3i) and 3-Pyridyl (3h) derivatives showed good antibacterial activity.
KEYWORDS: Antibacterial activity, antioxidant activity, 1,3,4-Oxadiazole.
INTRODUCTION:
Substituted 1,3,4-Oxadiazoles were reported to possess several interesting biological activities such as antimicrobial1, anticancer2, antioxidant activity3, antiinflammatory4, anti-fungal5, antimicrobial6 and antitubercular7 activities etc. These findings prompted us to synthesize novel 1,3,4-oxadiazoles with the hope of obtaining compounds with potent biological activity.
MATERIALS:
Carboxylic acids were procured from Merck, SD fine chemicals, Aldrich and Sigma. All other chemicals are of AR grade. All Melting points were determined using open capillary tube method and were uncorrected. The purity of the compounds was monitored by ascending thin layer chromatography (TLC) on silica gel G (Merck Kieselgel 60 F254) and visualized by iodine vapour. Developing solvents were chloroform: methanol (9:1). IR spectra were recorded using KBr on FTIR spectrometer and proton nuclear magnetic resonance (1H NMR) spectra were recorded on Bruker (400 MHz) Avance in DMSO-d6. Chemical shifts are reported in parts per million (ppm) using tetramethylsilane (TMS) as an internal standard. Mass spectra were performed on Agilent 6310 Ion Trap spectrometer under EI. The agar medium was purchased from HI Media Laboratories Limited, Mumbai, India.
METHODS:
Synthesis of naphthyl acetic acid ester (1):
A mixture of naphthyl acetic acid (0.246mol), absolute ethanol (2.5mol) and conc. H2SO4 (2.7ml) was refluxed for about 4h. The excess solvent was distilled off and allowed to cool and poured into crushed ice. The solution was extracted with carbon tetra chloride. CCl4 layer was collected and sodium bicarbonate was added to remove excess acid, then filtered. CCl4 layer was evaporated to get...