The predominant pathogen found in the lungs of cystic fibrosis (CF) patients is Pseudomonas aeruginosa. The success of the infection is partially due to virulence factor production, which is regulated by quorum sensing (QS) signaling. Currently, antibiotics are used to treat the infection, but resistant forms of P. aeruginosa have evolved, necessitating alternative treatments. Previous animal studies showed that treatment with extracts from the Chinese herb Panax ginseng C.A. Meyer reduced bacterial load resulting in a favorable immune response. It is hypothesized that ginsenosides, the major bioactive compounds in ginseng, is responsible for this effect. This study explores the role of ginseng extracts in attenuating P. aeruginosa virulence. A sequential extraction was performed using hexane, methylene chloride, methanol, and water. High performance liquid chromatography (HPLC) analysis showed the methanol and water ginseng extracts contained the known ginsenosides Rb1, Rb2, Rc, Rd, Re, and Rg1• All extracts were tested on biomonitor strains of Agrobacterium tumefaciens,Chromobacterium violaceum, and P. aeruginosa. Antibacterial and anti-QS activity were assessed using a disc diffusion assay. This was then followed by thin layer chromatography (TLC) bioautographic assay to further separate active compounds. The hexane and dichloromethane extracts, that lacked ginsenosides, displayed antibacterial activity against C. violaceum, whereas methanol and water extracts had anti-QS activity. The results of the bioassay with the pure ginsenoside standards showed that they lack antibacterial or anti-QS activity. Our results indicate that there are bioactive compounds, other than ginsenosides, that are the cause of antibacterial effects and anti-QS in the ginseng extracts.
