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Synthesis of Schiff Bases of 4-Amino-3-Mercapto-5-Pyridin- 4yl-4H-1,2,4-Triazole and Their Evaluation as Resistance Inducers and Antifungal Agents

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Title Synthesis of Schiff Bases of 4-Amino-3-Mercapto-5-Pyridin- 4yl-4H-1,2,4-Triazole and Their Evaluation as Resistance Inducers and Antifungal Agents
M.Sc.
 
Creator SUJAN MAJUMDER
 
Contributor R.L. Gupta
 
Subject fungi, acidity, organic compounds, planting, diseases, aromatic compounds, heterocyclic compounds, carbon, solutes, rice
 
Description Schiff bases are the products of aldehyde and primary amine and characterized by N=CH–
group. Schiff bases comprising of various heterocyclic moiety have found use as drugs and also
been reported as pesticides. Schiff bases of several series of 4-Amino-1,2,4-triazoles have
already been synthesized and their antifungal, antiviral and PGR activity have been reported.
Some 5–Aryl-4-amino 3-mercapto triazoles and their schiff bases have been reported as
fungicides and nematicides. Schiff bases of 4–amino-3-mercapto-5-pyridin-2yl-4H-1,2,4-tiazole
have recently been reported as nematicides. The use of chemicals to activate SAR provides a
novel alternative to plant disease control. 2,6-Dichloro isonicotinic acid (INA), is a well known
systemic acquired resistance (SAR) activator analogous in action to salicyclic acid. A series of
twenty five Schiff bases of 4-Amino-3-mercapto-5-pyridin-4yl-4H-1,2,4-triazole, incorporating
the isonicotinic acid moiety and having different substitution in the aryl ring attached to imine
group were designed and synthesized following the synthesis scheme which involved five steps
starting with isonicotinic acid which was first converted to→ ethyl ester→ hydrazide
→dithiocarbazinic salt→ triazole and then finally to Schiff bases. The products were
characterized by elemental analysis, FT–IR, 1HNMR and 13CNMR spectroscopy. Three of the
five steps of the synthesis i.e ethyl ester to hydrazide; dithiocarbazinic salt to triazole and
triazole to Schiff bases were accomplished using microwave. The microwave synthesis have
been found must faster(1-1.5 min) and efficient than the conventional method (2-4 hr). The
Schiff bases were obtained in good yields 44.4 to 86.9% (conventional) and 69.7 to 94.9%
(microwave).
All twenty five Schiff bases, 4-Arylidenamino-3-mercapto-5-pyridin-4-yl-4H-1,2,4-
triazoles were screened for systemic acquired resistance (SAR) inducing activity against sheath
blight of rice and five potential compounds viz 3-NO2 (GS6), 4-NO2 (GS7), 3-Br (GS18), 2-F
(GS20) and 4-F (GS21) analogs were further evaluated. All the five compounds considerably
decreased the relative lesion height (RLH) as compared to control with maximum reduction in
RLH shown by compound No. GS21 (47.15%). These five potential compounds were further
studied for their effect on phenol content, PAL and peroxides activity. The compound GS21,
4-(4-Flurobenzylidenamino)-3-mercapto-5-pyridin-4-yl-4H-1,2,4-triazole was identified as the
most potent SAR inducer both based on phenotypic and biochemical study. Its RI activity was
found better than 2,6-dichloroisonicotinic acid (INA), a resistance inducing
chemical used as standard.
The twenty five Schiff bases, 4-Arylidenamino-3-mercapto-5-pyridin-4-yl-4H-1,2,4-
triazoles were also evaluated in vitro for antifungal activity against R. solani and F. moniliforme.
The compounds in general showed moderate fungicidal activity against both the fungi. The
highest antifungal activity against both the fungi was exhibited by the compound GS19, 4-(4-
Bromobenzylidenamino)-3-mercapto-5-pyridin-4-yl-4H-1,2,4-triazole (ED50 (μg/ml)= 358,
R. solani and 460, F. moniliforme). The compound GS21, 4-(4-Flurobenzylidenamino)-3-
mercapto-5-pyridin-4-yl-4H-1,2,4-triazole, however, exhibited least activity (ED50 994 μg/ml)
against R. solani. The Schiff base GS21, 4-(4-Flurobenzylidenamino)-3-mercapto-5-pyridin-4-
yl-4H-1,2,4-triazole which exhibited the least fungicidal activity against R. solani was found to
be most potent and promising SAR inducer against sheath blight of rice.
 
Date 2016-03-21T18:56:10Z
2016-03-21T18:56:10Z
2013
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/65352
 
Language en_US
 
Format application/pdf
 
Publisher IARI, DIVISION OF AGRICULTURAL CHEMICALS INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI