Abstract
Ten novel isonicotinamide derivatives were prepared by quaternization reactions of isonicotinamide with methyl iodide and nine differently substituted 2 bromoacetophenones under rapid microwave irradiation of 10 minutes. The microwave preparations were significantly faster and with yields higher up to 8 times, than the preparations by conventional method. The structures of synthesized molecules were determined by one- and two dimensional NMR and IR spectroscopy, mass spectrometry and elemental analysis. Antifungal activity of all compounds was tested in two different concentrations (10 and 100 µg mL–1) against Fusarium oxysporum, Fusarium culmorum, Macrophomina phaseolina and Sclerotinia sclerotiorum in vitro. From the antifungal assay it can be seen that the most prepared compounds have moderate to weak activity against M. phaseolina and F. culmorum. A very high inhibitory rate was observed against S. sclerotiorum, 62–87.5 % in concentration of 10 µg mL–1 and 83.7–93.2 % in concentration of 100 µg mL–1.
Highlights
IntroductionT HE chemistry of carboxamide derivatives with various structural moieties have attracted much attention owing to their different biological properties: antimicrobial,[1,2,3,4,5,6] antifungal,[7,8,9,10] anti-inflammatory,[11] analgesic,[12,13] antitumoral,[14,15,16,17,18] antihypertensive,[19,20] anticonvulsant,[21,22] and antiviral [23] in the recent two decades
It has been proven that pyridine carboxamide group display fungicidal activity by disrupting the mitochondrial tricarboxylic acid cycle (TCA) through inhibition of the succinate dehydrogenase (SDH) enzyme, called succinate ubiquinone oxidoreductase (SQR).[29]
In a continuation of our previous work[33] in which we have confirmed the antifungal activity of nicotinamide derivatives obtained by quaternization of nicotinamide and substituted 2-bromoacetophenones, we have investigated here the effects of newly prepared isonicotinamide derivatives in vitro against four fungal pathogens (Fusarium oxysporum, Fusarium culmorum, Macrophomina phaseolina and Sclerotinia sclerotiorum)
Summary
T HE chemistry of carboxamide derivatives with various structural moieties have attracted much attention owing to their different biological properties: antimicrobial,[1,2,3,4,5,6] antifungal,[7,8,9,10] anti-inflammatory,[11] analgesic,[12,13] antitumoral,[14,15,16,17,18] antihypertensive,[19,20] anticonvulsant,[21,22] and antiviral [23] in the recent two decades. The bioassay results have shown that some of them exhibited excellent antifungal activities.[23,24,25,26,27,28] It has been proven that pyridine carboxamide group display fungicidal activity by disrupting the mitochondrial tricarboxylic acid cycle (TCA) through inhibition of the succinate dehydrogenase (SDH) enzyme, called succinate ubiquinone oxidoreductase (SQR).[29]. For example, is a pyridine carboxamide mainly used against Botrytis cinerea, Alternaria solani and Sclerotinia sclerotiorum on the fruits and vegetables.[30] Furametpyr and penthiopyrad contain a pyrazole ring in its structure. Penthiopyrad controls rust, Rhizoctonia and other diseases on cereals.[31] Carbendazim, thiabendazole and benomyl have benzimidazole moiety. Carbendazim is used to control plant diseases in cereals and fruits. Thiabendazole is a post-harvest fungicide mainly used to control a wide range of diseases for fruit and other crops (Aspergillus, Botrytis, Cladosporium, Fusarium spp.). Azoxystrobin, cyproconazole and mancozeb belong to strobilurin and dithiocarbamates groups of compounds
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