Research on the Antibacterial Effects of Extracts from Magnolia officinalis Bark on the Pathogen of Potato Bacterial Wilt

[Objective] The research aimed to develop the bioactive substance in Magnolia officinalis into biological bactericide. [Method] The extraction experiment was conducted by ASE300 accelerated solvent extraction machine and the contents of phenolic compounds were determined by HPLC. The sizes of bacteriostatic circles were measured by paper disc method and the minimum inhibition concn. (MIC) was determined by poison media technique. [Result] The extracts from 100 g dry M. officinalis bark contained 2.86 g total phenolic compounds, in which honokiol was 1.76 g and magnolol was 1.10 g. When the concn. of total phenolic compounds in the extracts from M. officinalis bark was 0.6, 0.3, 0.2 and 0.1 mg/ml, the extracts showed stronger bacteriosatic activity on the tested pathogen of potato bacterial wilt with sizes of bacteriostatic circles being 23.1, 22.9, 18.1 and 13.7 mm resp. The MIC of extracts from M. officinalis bark on the tested pathogen of potato bacterial wilt was 0.1 mg/ml. [Conclusion] The total phenolic compounds in most M. officinalis barks could be extracted by the extraction used in the experiment and the extracts showed stronger bacteriosatic activity.