Synthesis of Thiazolium-Labeled 1,3,4-Oxadiazole Thioethers as Prospective Antimicrobials: In Vitro and in Vivo Bioactivity and Mechanism of Action

In
this study, a type of thiazolium-labeled 1,3,4-oxadiazole thioether
bridged by diverse alkyl chain lengths was constructed. The antimicrobial
activity of the fabricated thioether toward plant pathogenic bacteria
and fungi was then screened. Antibacterial evaluation indicated that
title compounds possess specific characteristics that enable them
to severely attack three phytopathogens, namely, Xanthomonas
oryzae pv. oryzae, Ralstonia solanacearum, and Xanthomonas
axonopodis pv. citri with minimal
EC50 values of 0.10, 3.27, and 3.50 μg/mL, respectively.
Three-dimensional quantitative structure–activity relationship
models were established to direct the following excogitation for exploring
higher active drugs. The in vivo study against plant bacterial diseases
further identified the prospective application of title compounds
as alternative antibacterial agents. The proteomic technique, scanning
electron microscopy patterns, and fluorescence spectrometry were exploited
to investigate the antibacterial mechanism. Additionally, some target
compounds performed superior inhibitory actions against three tested
fungal strains. In view of their simple molecular architecture and
highly efficient bioactivity, these substrates could be further explored
as promising surrogates for fighting against plant microbial infections.