Extraction, Bacteriostatic Effect and Synergistic Mechanism of Bacteriostatic Effect of Taxifolin in Larch in Combination with Leucocyanidin

Using larch as raw material, taxifolin was extracted by ultrasonic-assisted ethanol hot leaching. Escherichia coli and Staphylococcus aureus were used as typical test bacteria respectively, and the bacterial inhibitory effects of taxifolin was analyzed by observing the morphological structure of bacteria and measuring the changes in bacterial growth, cell membrane leakage and antioxidant enzyme system activities. The final product was obtained with 90% purity and 0.35% extraction rate of taxifolin. The minimum inhibitory concentration of taxifolin was 1.2 mg/mL for both strains, and the inhibition rate was 81.12% and 83.95%, respectively. After the electron microscopy analysis, the surface of the bacteria cells was disrupted and the contents inside the cells were leaked. In E. coli, the OD₂₆₀ test values of 1/2 MIC, 1 MIC and 2 MIC were 1.18, 1.52 and 1.88 times higher than those of the control group after 24 h incubation. The relative activities of extracellular β-galactosidase were 79.15% and 70.1%, respectively, and the growth rate calculated by the the Bliss independent model was 0.0142. S. aureus showed a synergistic inhibition effect. Under the conditions of drug combination, the bacterial cell membrane disruption extent was significantly enhanced by the low concentration and the inhibition effect was more significant. The β-galactosidase activity in the culture supernatant was 87.01% higher than that of 2 MIC group alone for S. aureus by 16.91%, and the 24 h CAT, SOD and POD enzyme activities were higher than that of 1 MIC group alone for S. aureus, which were 1.28, 1.25 and 1.11 times higher, respectively. The study could lay the theoretical foundation for the development and application of taxifolin as a food preservation and preservative.