Apigenin promotes antibacterial activity via regulation of nitric oxide and superoxide anion production

Apigenin is a naturally occurring flavone isolated from the medicinal herb, Aster yomena. The present study was designed to elucidate the apoptosis-like antibacterial mechanism of apigenin in Escherichia coli. Administration of apigenin resulted in a rapid increase in intracellular calcium accompanied by an increase in reactive nitrogen species (RNS) and nitric oxide (NO) levels. Furthermore, apigenin increases reactive oxygen species (ROS), superoxide anion (O₂ ^- ) which left E. coli with no ability to activate superoxide dismutase. Finally, we found that perturbance of the membrane lipid bilayer leading to glutathione oxidation and formation 8-hydroxy-2'-deoxyguanosine occurred during the process and apoptosis-like death hallmarks were further observed. Furthermore, we applied the NO synthase inhibitor ( l-NAME) and the O₂ ^- scavenger (Tiron) and observed attenuation in apoptotic markers under their presence. Taken together, these results suggest that apigenin induces bacterial apoptosis via activation of cellular oxidative pathways dependent on the production and accumulation of RNS/ROS.

Keywords: Escherichia coli; apigenin; apoptosis-like death; nitric oxide; phytochemical; superoxide anion.