Membrane-damage antibacterial mechanism of phenanthrene compounds from Arundina graminifolia (D.Don) Hochr

Arundina graminifolia (D. Don) Hochr. is an ethnic medicine that has been used as an antidote for food poisoning and urinary tract infection by Dai minorities for centuries. However, its pharmacological mechanism of antibacterial activity and efficacy components are not clearly defined. Thirteen compounds were isolated from the whole plant of A. graminifolia and their structures were identified by spectroscopic analysis, and their antibacterial effects against Escherichia coli and Staphylococcus aureus were tested by micro-broth dilution method. Four compounds (6, 11, 12 and 13) possessed excellent antibacterial activities. Among them, blestiarene A (11) and densiflorol B (13) triggered significant bacteriostatic efficacy with the minimum inhibitory concentration between 25-50 μg/mL (positive drug amoxicillin 0.3-0.6 μg/mL). Mechanism research showed that compound 11 and 13 increased the level of reactive oxygen species and altered the bacterial membrane structure, leading to leakage of alkaline phosphatase and DNA, which consequently caused the death of bacteria. In addition, density functional theory calculation showed that the electron affinity of the antibacterial agent was positively correlated with antibacterial activity. Our work highlighted the antibacterial potential of natural phenanthrenes with membrane disrupt mechanism, and the tested phenanthrene derivatives could serve as lead compounds for the novel bactericides.