Extract from Maize (Zea mays L.): Antibacterial Activity of DIMBOA and Its Derivatives against Ralstonia solanacearum

Many cereals accumulate hydroxamic acids involved in defense of plant against various fungi, bacteria, and insects. 2,4-dihydroxy-7-methoxy-1,4-benzoxazine-3-one, commonly known as DIMBOA, is one of the principal cyclic hydroxamic acids in aqueous extracts of maize. The aim of this study was to evaluate the antibacterial activity of the isolated DIMBOA and its derivatives 2-benzoxazolinone (BOA), 6-chloro-2-benzoxazolinone (CDHB), and 2-mercaptobenzothiazole (MBT) against Ralstonia solanacearum. MBT showed the strongest antibacterial activity, followed by CDHB and DIMBOA, with minimum inhibitory concentrations (MICs) of 50, 100 and 200 mg/L, respectively, better than the BOA with 300 mg/L. These compounds also significantly affect bacterial growth, reduce biofilm formation, and inhibit swarming motility within 24 h. This paper is the first to report the anti-R. solanacearum activity of DIMBOA from Z. mays. The bioassay and pot experiment results suggested that DIMBOA and its derivatives exhibit potential as a new matrix structure of designing target bactericide or elicitor for controlling tobacco bacterial wilt. Further studies must evaluate the efficacy of DIMBOA and its derivatives in controlling bacterial wilt under natural field conditions where low inoculum concentrations exist.