Design, synthesis and biological evaluation of 1,3,4-oxadiazoles/thiadiazoles bearing pyrazole scaffold as antimicrobial and antioxidant candidates

A series of semicarbazones, thiosemicarbazones, 1,3,4-oxadiazoles/thiadiazoles bearing pyrazole scaffold were designed and synthesized. All the synthesized new compounds were characterized by 1H NMR, 13C NMR, MS and elemental analysis.
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Design, synthesis and biological evaluation of 1,3,4-oxadiazoles/thiadiazoles bearing pyrazole scaffold as antimicrobial and antioxidant candidates Current Chemistry Letters 5 (2016) 109–122 Contents lists available at GrowingScience Current Chemistry Letters homepage: www.GrowingScience.comDesign, synthesis and biological evaluation of 1,3,4-oxadiazoles/thiadiazolesbearing pyrazole scaffold as antimicrobial and antioxidant candidatesPavithra Gurunanjappa and Ajay Kumar Kariyappa*Post Graduate Department of Chemistry, Yuvaraja’s College, University of Mysore, Mysuru 570005, IndiaCHRONICLE ABSTRACT Article history: A series of semicarbazones, thiosemicarbazones, 1,3,4-oxadiazoles/thiadiazoles bearing Received October 21, 2015 pyrazole scaffold were designed and synthesized. All the synthesized new compounds were Received in revised form characterized by 1H NMR, 13C NMR, MS and elemental analysis. The synthesized compounds December 20, 2015 were screened to probe their in vitro antimicrobial activity against bacteria and fungi species. Accepted 12 Februray 2016 The structure-activity relationship of the synthesized compounds was studied. The compounds Available online displayed good to excellent potency against tested microorganisms. The in vitro antioxidant 12 February 2016 activities of the 1,3,4-oxadiazoles/thiadiazoles were evaluated by DPPH, hydroxyl and nitric Keywords: oxide radical scavenging assay. Among the tested compounds, compound with chloro Antimicrobial Antioxidant substitution showed good antioxidant potential. Pyrazole Semicarbazone Thiosemicarbazone © 2016 Growing Science Ltd. All rights reserved.1. Introduction The pyrazole motif makes up the core structure of numerous biologically active compounds.Compounds bearing pyrazole nucleus exhibit versatile range of biological activities such asantimicrobial1, anti-inflammatory2, analgesic3 and GABA receptor antagonists and insecticides.4 Inaddition to the diverse biological activities of pyrazoles, other heterocycles in association withpyrazoles play a prime role in chemical and pharmacological fields. The prevalence of pyrazole coresin biologically active molecules has stimulated the need for elegant and efficient ways to make theseheterocyclic lead. Further, semicarbazone and thiosemicarbazone are excellent prototypes for the design anddevelopment of novel amino oxadiazole and thiadiazole respectively. In addition semicarbazone havereceived significant attention from pharmaceutical industry due to their wide spectrum of biologicalactivity such as anticonvulsant,5 antioxidant,6 antimicrobial activities7 etc. Compounds containing1,3,4-oxadiazole core were known to possess pharmacological properties such as antimicrobial,8 COX-2 inhibitors and anti-inflammatory, antitumor and analgesic.9 The widespread use of 1,3,4-oxadiazoles* Corresponding author. E-mail address: ajaykumar@ycm.uni-mysore.ac.in (A. K. Kariyappa)© 2015 Growing Science Ltd. All rights reserved.doi: 10.5267/j.ccl.2016.2.002110 as a scaffold in medicinal chemistry established this moiety as a member of the privileged structuresclass, among them the synthesis of 2-amino-5-substituted-1,3,4-oxadiazole has received a lot ofinterest. Sulpha drugs are well recognized for their various physiological activities. Thiosemicarbazonederivatives have been the focus of medicinal chemists because of their potential biological activities.10Thiosemicarbazones are very useful intermediate for the development of molecules ofpharmaceutically important molecules, as well as they themselves possess antimicrobial, antiviral,11anti-HIV12 and anticancer13 properties. 1,3,4-Thiadiazoles have gained importance as they constitutethe structural features of many bioactive compounds. These compounds are of great interest inchemistry owing to their bioactivity of certain plant growth regulating effects as well as antimicrobialactivity.14 1,3,4-Thiadiaz ...