Novel piperazine-tailored ursolic acid hybrids as significant antibacterial agents targeting phytopathogens Xanthomonas oryzae pv. oryzae and X. axonopodis pv. citri probably directed by activation of apoptosis.

Background: Induced apoptosis is an effective technique that can reprogram cellular physiological and pathological processes to eradicate undesirable cells using their innate systems. Inspired by this, numerous apoptosis inducers have been developed to treat animal diseases, especially in the anticancer field. However, few studies have reported on the development of inductive agents that attack plant pathogens by activation of apoptosis. With the aim of exploring and discovering apoptosis inducers that target phytopathogens, a cluster of piperazine-tailored ursolic acid (UA) hybrids was systematically fabricated.

Results: In vitro testing showed that the title molecules could inhibit the growth of two intractable bacterial strains, defined as Xanthomonas oryzae pv. oryzae and X. axonopodis pv. citri. The corresponding lowest EC values were 0.37 and 1.08 μg mL , which exceed those of UA (>400 μg mL ) and positive controls. Moreover, compounds 5u and 5v could manage bacterial blight in vivo using pot experiments. Flow cytometer analysis indicted that the title compounds could induce distinct apoptotic behaviors on tested bacteria. In-depth study revealed that the introduction of designed compounds could reduce the enzyme activities of catalase and superoxide dismutase, subsequently leading to the accumulation of reactive oxygen species.

Conclusion: This study promoted the development of apoptosis initiators for managing bacterial infections in agriculture by an innovative mode of action. © 2020 Society of Chemical Industry.