Antibacterial mode of action of 1,8-dihydroxy-anthraquinone from Porphyra haitanensis against Staphylococcus aureus.

As one kind of anthraquinone dihydroxy derivatives, 1,8-dihydroxy-anthraquinone (Dan) with strong antibacterial activity against Staphylococcus aureus was first isolated from Porphyra haitanensis. Here, we report on the investigation of the antibacterial mode of action of Dan on the Gram-positive bacterium S. aureus. The results show that Dan strongly inhibited cell growth at logarithmic phase. In this study, the antibacterial activity of Dan was analysed by using phosphorus standard solution, p-nitrophenyl phosphate, o-nitrophenyl-β-D-galactopyanoside, scanning electron microscopy and transmission electron microscopy. The results suggested that the antibacterial activity of Dan is due to its interaction with the cell wall and cell membrane, by which it increases the permeability of the cell envelope and leads to the leakage of cytoplasm and the deconstruction of cell. This study indicates that Dan as a natural product in seaweeds deserves further investigation for applications as an antibacterial bioactive substance in food safety control and drugs.