Abstract:Our previous studies have shown that the chloroform extracts from Ziziphus jujuba Mill. var. spinosa fruits has a broad-spectrum antimicrobial synergism. And we further extracted the low-polarity active ingredient Fr.2a from the chloroform extracts, and found that Fr.2a showed a wide range of synergistic antimicrobial effects when used in combination with a variety of antibiotics. However, since the activity of Fr.2a is inferior to that of chloroform extracts, we speculate that there were substances in the other polar range of chloroform extracts from Ziziphus jujuba Mill. var. spinosa fruits that might also have antimicrobial synergistic activities. For this reason, this study further analyzed and studied the antimicrobial synergists in other polar range of the chloroform extracts from Ziziphus jujuba Mill. var. spinosa fruits. On the basis of Fr.2a, the active components in other polar range of the chloroform extracts from Ziziphus jujuba Mill. var. spinosa fruits were separated and purified by silica gel column chromatography, and the refined product Fr.B was obtained. Then, we analyzed Fr.B by GC-MS, hydrogen nuclear magnetic resonance spectroscopy (1H-NMR), infrared spectroscopy (IR), determination of antimicrobial synergistic spectrum and study of antimicrobial synergistic mechanism, and prepared Fr.B into ointment, and evaluated the synergistic effect of the ointment on antibiotics in vivo and in vitro. The results were as follows: (1) The Fr.B component obtained by further refining the chloroform extracts of Ziziphus jujuba Mill. var. spinosa fruits, after GC-MS, 1H-NMR, and IR analysis showed that it mainly contains fatty acid compounds such as elaidic acid, oleic acid, cis-10-hexadecenol, palmitic acid and so on. (2) Fr.B showed a wide range of synergistic antimicrobial effects when combined with a variety of antibiotics. (3) The antimicrobial synergistic mechanism of Fr.B may be to enhance the antimicrobial effect of antibiotics on resistant organism by changing the permeability of cells. (4) Fr.B could significantly enhance the bactericidal effect of erythromycin on methicillin-resistant Staphylococcus aureus (MRSA) in vivo and in vitro, thereby improving the therapeutic effect of erythromycin on wound infections caused by MRSA strains. In conclusion, Fr.B obtained in this study has a broad spectrum of antimicrobial synergistic activity, which can enhance the efficacy of erythromycin in the treatment of wound drug-resistant bacteria infection. This provides new ideas and solutions for overcoming microbial resistance to antibiotics.