Synthesis and activity evaluation of new benzofuran-1,3,4-oxadiazole hybrids against wood-degrading fungi

Abstract

A series of novel benzofuran-1,3,4-oxadiazole hybrids were synthesized and evaluated as antifungal agents. The synthetic pathway was started from salicylaldehyde, which afforded 5-(substituted benzylthio)-1,3,4-oxadiazole derivatives in moderate to good yields. The compounds were investigated for their antifungal potential against white-rot, Trametes versicolor and brown-rot, Poria placenta and Coniophora puteana fungi at different concentrations (500, 1000 ppm). The obtaining results demonstrated that most of the compounds at 500 ppm concentration did not exhibit acceptable antifungal effects but they had better antifungal activity at 1000 ppm concentration. Compounds 5a, 5c, and 5i showed inhibition percentages of 14.6%, 23.0%, and 14.7%, against the growth of P. placenta and C. puteana, respectively. Among the compounds, the 2-(benzofuran-2-yl)-5-((2,6-difluorobenzyl)thio)-1,3,4-oxadiazole (5h) hybrid was the most active one.

Design and synthesis of new benzofuran-1,2,3-triazole hybrid preservatives and the evaluation of their antifungal potential against white and brown-rot fungi

“…The presence of a methyl group provided similar activity to ketoconazole against T. versicolor and P. placenta at 1000 ppm (Hosseinihashemi et al 2020). A strong electron-donating group (methoxy group) with a meta position resulted in better activity against P. placenta than a para position at 1000 ppm.…”

“…Ketoconazole, as the representative synthetic fungicide (at 500 ppm and 1000 ppm concentrations), was used as the positive control due to its inhibitory effects against radial growth of three wood-degrading fungi, i.e., T. versicolor, P. placenta, and C. puteana. Methanol was selected as the negative control to confirm that there was no inhibitory effect (Teoh et al 2015;Hosseinihashemi et al 2020).…”

“…The percentage of fungal mycelial growth was plotted against the compound concentration, and the toxicity level was determined by the compound concentration. In other words, the fungal growth was monitored daily by measuring the percentage of area that was covered by fungus in the test plates until one day prior to complete coverage of Petri plate, similar to reported methods (Hosseinihashemi et al 2016a(Hosseinihashemi et al , 2016bHosseinihashemi et al 2020).…”

“…A strong electron-donating group (methoxy group) with a meta position resulted in better activity against P. placenta than a para position at 1000 ppm. When the authors changed the position of the -F substitution (strong electron-donating group) in the new benzofuran-1,2,3-triazole hybride synthetic fungicide from the previous benzofuran-1,3,4-oxadiazole hybrid synthetic fungicide 5h (meta to para position) led to more a potent compound 8f at 500 ppm against C. puteana and specially G. trabeum (Hosseinihashemi et al 2020). However, this effect was not observed at 1000 ppm, which could be related to the low solubility of the compound at this concentration in the MEA medium.…”

“…Reports by Hosseinihashemi et al (2020), in regards to the effects of new benzofuran-1,3,4-oxadiazole hybrids on the inhibition of mycelial growth in wooddegrading fungi, showed that most of the compounds at 500 ppm concentration did not exhibit acceptable antifungal effects, but they had better antifungal activity at 1000 ppm concentration. Compounds 5a, 5c, and 5i at a concentration of 1000 ppm showed inhibition percentages of 14.6%, 23.0%, and 14.7%, respectively, against the growth of P. placenta and C. puteana.…”