Antibiofilm activity against Staphylococcus aureus and content analysis of Taraxacum Officinale phenolic extract

Taraxacum Officinale, commonly called dandelion, is herbaceous perennial belonging to the family of Asteraceae, having good antibacterial effects which are related to its phenolic substances. In this study, the effect of phenolic contents as well as the antibiofilm activity against Staphylo- coccus aureus of phenolic extract from T. Officinale were evaluated in vitro. With 70% metha- nol-water (v/v) as a solvent, the dandelion was extracted by ultrasonic assisted extraction method. Subsequent identification and quantification of phenol in extract was carried out using High Performance Liquid Chromatography (HPLC). The minimum inhibitory concentration and anti- bacterial kinetic curve of dandelion phenolic extract were analyzed by spectrophotometry. Changes in extracellular alkaline phosphatase (AKP) contents, electrical conductivity, intracellular protein contents, and DNA of S. aureus after the action of dandelion phenolic extract were determined to study its effect on the permeability of S. aureus cell wall and cell membrane. The results showed that chlorogenic acid (1.34 mg/g) was present in higher concentration, followed by lute- olin (1.08 mg/g), ferulic acid (0.22 mg/g), caffeic acid (0.21 mg/g), and rutin (0.19 mg/g) in the dandelion phenolic extract. The minimum inhibitory concentration (MIC) of dandelion phenolic extract against S. aureus was 12.5 mg/mL. The antibacterial kinetic curve analysis showed that the inhibitory effect of dandelion phenolic extract on S. aureus was mainly in the exponential growth phase. After applying the dandelion phenolic extract, the growth of S. aureus was signifi- cantly inhibited entering into the decay phase early. Furthermore, after the action of dandelion, the extracellular AKP contents of S. aureus, the electrical conductivity and the extracellular protein contents were all increased. The phenolic extract also affected the normal reproduction of S. aureus. These results suggest that dandelion has an inhibitory effect on S. aureus, and the mechanism of its action was to destroy the integrity of the cell walls and cell membranes.