Abstract:

The study aimed to reveal the antibacterial activity of dandelion polyphenols （DP） against common skin pathogens and anti-inflammatory activity. In this study, six common skin pathogens were treated with different concentrations of dandelion polyphenols for 24 hours, and the minimum inhibitory concentration （MIC） and the diameter of bacteriostatic zone were measured. CCK-8 kit was used to detect the toxicity of dandelion polyphenols to RAW264.7 cells. RAW264.7 cells were divided into Blank group, LPS group, LPS+10 DP group, LPS+50 DP group, LPS+100 DP group, LPS+200 DP group, LPS+400 DP group, LPS+800 DP group and LPS+1 600 DP group. The cells were treated with saline, LPS （1 μg/mL） and different concentrations of dandelion polyphenols for 24 hours. The content of NO was measured by visible spectrophotometry. The mRNA levels of inducible nitric oxide synthase （iNOS）, cyclooxygenase-2 （COX-2）, tumor necrosis factor-α （TNF-α）, interleukin （IL）-1β and IL-6 were detected by RT-qPCR. The phosphorylation levels of NF-kappa B （NF-κB） p65 and p38 mitogen activated protein kinase （MAPK） were detected by Western blotting. The nuclear translocation of NF-κB p65 was observed by immunofluorescence staining. The results show that the MIC of dandelion polyphenols against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris and Cutibacterium acnes are 400, 400, 400, 800, 800 and 400 μg/mL, respectively. When the concentration of dandelion polyphenols is over 800 μg/mL, all the six pathogens have obvious bacteriostatic circles （P<0.001）. The concentration of dandelion polyphenols in the range of 10 to 1 600 μg/mL is non-toxic to RAW264.7 cells （P>0.05）. Compared with LPS group, NO content and relative levels of iNOS, COX-2, TNF-α, IL-1β and IL-6 mRNA in RAW264.7 cells in LPS+100 DP group, LPS+200 DP group, LPS+400 DP group, LPS+800 DP group and LPS+1 600 DP group decrease （P<0.05）, the relative phosphorylation levels of NF-κB p65 and p38 MAPK decrease （P<0.05）, and the nuclear translocation of NF-κB p65 decreases. The above results indicate that dandelion polyphenols have antibacterial activity against common skin pathogens, and can inhibit LPS-induced RAW264.7 cell inflammation and the activation of NF-κB p65 and p38 MAPK signaling pathways.

Key words: dandelion polyphenols, common skin pathogens, bacteriostasis, anti-inflammation, nuclear factor-κB, p38 mitogen-activated protein kinase