Abstract
In the category of microorganism, fungi are considered as the special class of microbes responsible for opportunistic pathogenic infections in humans species. Due to the side effects of commercially available antifungal drugs and the emergence of new drug resistant fungal species in the past few years has forced the researchers to search for novel and efficient antifungal drug molecules. The 1,3,4-oxadiazoles scaffold is associated with diverse biological activities. The multipurpose use of the Mannich bases in pharmaceutical chemistry provoked us to prepare a new series of 1,3,4-oxadiazole Mannich bases derivatives, as antifungal agents. Herein we report Molecular sieves and Ultrasound assisted synthesis of novel series of Mannich bases of the 5-substituted 1,3,4-oxadiazole-2-thiones by amino methylation with paraformaldehyde and substituted primary / secondary amines and their evaluation for antifungal activity .The structures of the newly synthesized compounds were determined by IR, NMR and Mass spectral study. The synthesized compounds exhibited interesting moderate to excellent antifungal activity against Candida albicans (NCIM 3557),Candida albicans(NCIM3471), Candida glabrata(NCIM3237), Cryptococcus neoformans (NCIM 3542),Cryptococcus neoformans(NCIM 3378),Aspergillus fumigates(NCIM 902), Aspergillus niger( NCIM 628) using Flucanazole as a standard reference drug. The synthesised compounds 6d, 6f ,6g, 6h and 6j exhibited promising antifungal activity as fungi static agents.
Highlights
In the category of microorganism, fungi are considered as the special class of microbes responsible for opportunistic pathogenic infections in plant, animals and humans species
Available broad-spectrum antifungal drugs includes fluconazole, itraconazole, miconazole and voriconazole in which the mechanism of action is on target CYP51 which get inhibited and in turn switch off the biosynthesis of ergo sterols[1] .But the frequent use of these antifungal drugs in immune compromised patients who are undergoing the long term treatment of broad-spectrum antibiotics may be in cases of HIV infection, grafting surgery or anticancer therapy [2], has led to the development of resistance fungal strains
It can be considered as important tool for conservation of energy and minimization of waste as compared to the conventional techniques [26].we introduced ultrasound- promoted Mannich reaction of the 5-substituted 1,3,4-oxadiazole-2-thiones with primary and secondary amines and its antifungal screening because of the structural resemblance with established antifungal molecule triazoles
Summary
In the category of microorganism, fungi are considered as the special class of microbes responsible for opportunistic pathogenic infections in plant, animals and humans species. The physical characterization and spectral data of synthesized derivatives is as follows: 5-(4-(benzyloxy) phenyl)-3-(((4-chlorophenyl)amino)methyl)-1,3,4-oxadiazole-2(3H)-thione: Recrystallization from methanol; yield: 81%; m p: 1800C; IR (KBr), mmax/cm_1: 3235 (NH), 1621 (C=N), 1596 (C-C), 1425 (C=S), 1258 and 1093 (C–O–C), 820, 744; 1H NMR (CDCl3), δ ppm: 4.0 ( S,1H, -NH), 4.42( S,2H, N-CH2-N- ) 5.16 (S,2H, -OCH2), 6.54–8.02 (m, 13H, aromatic rings). IR (KBr), mmax/cm_1: 3550–3235 (NH), 1615 (C=N), 1593 (C-C), 1425 (C=S), 1250 and 1152 (C–O–C), 761, 739, 705; 1H NMR (CDCl3 + DMSO-d6), δ ppm: 4.0 ( S,1H, -NH), 4.42( S,2H, N-CH2-N- ) 5.16 (S,2H, -OCH2), 6.77–8.02 (m, 14H, aromatic rings) 4-(((5-(4-(benzyloxy)phenyl)-2-thioxo-1,3,4-oxadiazol-3(2H)-yl)methyl)amino)benzoic acid: Recrystallization from methanol; yield: 79%; mp: 1400C;. Whereas Minimum Inhibitory Concentration MIC90 was the concentration causing>90% inhibition of the growth as compared to the growth of control
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