Preparation of gallic acid-hydroxypropyl-β-cyclodextrin inclusion compound and study on its effect mechanism on Escherichia coli in vitro

The purpose of this paper is to optimize the preparation process of gallic acid-hydroxypropyl-β-cyclodextrin inclusion compound and to study its antibacterial effect in vitro. Orthogonal test was used to screen the preparation method of the compound. The microscopic appearance of the compound was observed by microscope, and the solubility of the compound was detected by the dissolution method. The antibacterial activity of the compound was measured by the Oxford cup method. Under the transmission electron microscope, the microstructure of the cells and the intracellular ultrastructure changes were observed. The results showed that when the molar ratio of gallic acid and hydroxypropyl-β-cyclodextrin inclusion was 1:1, the ethanol concentration was 80%, the inclusion temperature was 30 °C, and the inclusion time was 0.5 h, the inclusion effect was the best with an inclusion rate of 99.45%; the solubility of gallic acid before the inclusion was (6.515 ±0.55) mg/mL, while after the inclusion, the solubility increased by more than 100 times to (710.048 ±1.08) mg/mL; gallic acid-hydroxypropyl-β-cyclodextrin inclusion compound could dissolve and destroy the cell membrane of Escherichia coli. The preparation process of gallic acid-hydroxypropyl-β-cyclodextrin inclusion compound was stable and feasible, and there was a good inclusion effect. After the inclusion, the solubility of gallic acid increased significantly; the prepared inclusion compound could inhibit the gram-negative bacteria Escherichia coli by destroying the integrity of the bacterial cell membrane, which could provide data support for the application and development of gallic acid.