Isolation, Characterization and Antibacterial Activity of 4-Allylbenzene-1,2-diol from Piper austrosinense .

Isolation for antibacterial compounds from natural plants is a promising approach to develop new pesticides. In this study, two compounds were obtained from the Chinese endemic plant using bioassay-guided fractionation. Based on analyses of H-NMR, C-NMR, and mass spectral data, the isolated compounds were identified as 4-allylbenzene-1,2-diol and (S)-4-allyl-5-(1-(3,4-dihydroxyphenyl)allyl)benzene-1,2-diol. 4-Allylbenzene-1,2-diol was shown to have strong antibacterial activity against four plant pathogens, including pathovar (), pv. (), pv. () and pv. (). Further bioassay results exhibited that 4-allylbenzene-1,2-diol had a broad antibacterial spectrum, including , , , , (), pv. (), subspecies ) and subsp. (), with minimum inhibitory concentration (MIC) values ranging from 333.75 to 1335 μmol/L. The pot experiment showed that 4-allylbenzene-1,2-diol exerted an excellent protective effect against , with a controlled efficacy reaching 72.73% at 4 MIC, which was superior to the positive control kasugamycin (53.03%) at 4 MIC. Further results demonstrated that the 4-allylbenzene-1,2-diol damaged the integrity of the cell membrane and increased cell membrane permeability. In addition, 4-allylbenzene-1,2-diol also prevented the pathogenicity-related biofilm formation in , thus limiting the movement of and reducing the production of extracellular polysaccharides (EPS) in . These findings suggest the value of 4-allylbenzene-1,2-diol and could be as promising resources for developing novel antibacterial agents.