Preparation of oligomeric dehydrogenation polymer and characterization of its antibacterial properties

To investigate the relationship between the chemical structural characteristics of lignin and its antibacterial activity, a low molecular weight dehydrogenation polymer (DHP) was synthesized in vitro with isoeugenol as a precursor and catalyzed by laccase. The DHP was fractionated to obtain a petroleum ether-soluble fraction (F1), diethyl ether-soluble fraction (F2), ethanol-soluble fraction (F3), and acetone-soluble fraction (F4). The results of antibacterial experiments showed that only F1 and F2 could effectively inhibit the growth of Escherichia coli and Staphylococcus aureus. Furthermore, nine compounds (Z1 to Z9) were obtained via the column chromatographic separation from F1 and F2. Mass spectrum analysis results showed that all of these compounds contained a β-5 structure. Antibacterial experiments showed that dimers (Z1 and Z2) could inhibit both S. aureus and E. coli. The trimers, tetramers, and pentamers (Z3 to Z9) could inhibit S. aureus but had no inhibitory effect on E. coli. The aldehyde groups and the condensed 5-5 structure, decreased the antibacterial properties of DHP, whereas the presence of the β-5 structure may be related to the antimicrobial ability of DHP.