The antibacterial mechanism of pterostilbene derived from xinjiang wine grape: A novel apoptosis inducer in Staphyloccocus aureus and Escherichia coli

Antibiotic overuse has caused concerns owing to the emergence of antibiotic resistant microorganisms and the accompanying decreased bacteria-inhibiting effectiveness of proffered treatments. Pterostilbene, derived from XinJiang wine grape, is a natural polyphenol, and has attracted considerable attention for its promising anti fungal effects. However, its inhibitory activities and mechanisms of action against bacteria are still unknown. In this study, pterostilbene inhibited the growth of Gram-positive Staphyloccocus aureus and Gram-negative Escherichia call effectively. Electron microscope observations showed that the morphological structures of S. aureus and E. coil were significantly damaged by pterostilbene. Cells became irregular, shriveled, and lysed, while nucleic acids and proteins leaked, and DNA content decreased. Furthermore, confocal laser scanning microscopy experiments revealed that bacteria treated with pterostilbene produced reactive oxygen species, and the cytomembrane potential increased. To further clarify the molecular mechanism, changes in the expression levels of four genes in two bacteria were confirmed by qRT-PCR. Pterostilbene cause the up-regulation of DinF (an oxidative stress gene). An associated down-regulation of PaL, MtgA, and NagA (genes involved in cell wall synthesis) is also attributed to pterostilbene treatment. This is the first time that the mechanism of pterostilbene against S. aureus and E. coil is presented in literature.