High Throughput Screening of Bacteriostatic Activity in Different Polar Parts of Extracts of Leaves of Malus doumeri and Spectrum-Effect Relationship Analysis

OBJECTIVE To realize rapid and efficient screening and evaluation of antibacterial activity of different polar parts of the ethanol extracts of leaves of Malus doumeri, and to study the relationship between HPLC fingerprint and their antimicrobial activity, in order to determine the antibacterial material basis of leaves of Malus doumeri. METHODS HPLC was used to establish the fingerprint of different polar parts of the ethanol extracts of leaves of Malus doumeri. The anti-Staphylococcus aureus activities of different polar parts of the ethanol extracts of leaves of Malus doumeri were evaluated by high-throughput screening method with resazurin assay. Calculated the bacteriostatic rate of different polar parts at different concentrations to screen the antibacterial active parts of the ethanol extracts of leaves of Malus doumeri. Spectrum-effect relationship between the common peaks of each polar part and the antibacterial activity was established by least squares regression, selected the largest contribution of common peaks. Finally, effective peaks were identified by UPLC-Q-TOF/MS². RESULTS A total of 15 common peaks were picked up in the fingerprint of different polar parts of the ethanol extracts of leaves of Malus doumeri. The results showed that the order of antimicrobial activity was ethyl acetate fraction>n-butanol fraction/dichloromethane fraction>petroleum ether fraction>water fraction. Peak 8, peak 9, peak 10 and peak 15 showed high contribution to antibacterial activity, which were identified as quercetin 7-O-β-D-glucopyranoside, isoquercetin, phlorizin and chrysin. CONCLUSION The ethyl acetate fraction is the antibacterial active polar parts of the ethanol extracts of leaves of Malus doumeri. The HPLC spectrum-effect relationship suggests that quercetin 7-O-β-D-glucopyranoside, isoquercetin, phlorizin and chrysin are the antibacterial active components, but it remains to be further explored whether there are other trace antibacterial active ingredients in leaves of Malus doumeri.