Abstract
A large number of Chinese herbal drugs (CHDs) exhibit antibacterial activities both in vivo and in vitro, but until now little is known regarding their inhibitory mechanisms. Bacterial DNA gyrase is a proven target for antibacterial agents. Aim of this study was to investigate the in-vitro inhibitory effect of methanol extracts of CHDs against supercoiling activity of bacterial DNA gyrase. Fifteen CHDs were selected and extracted with methanol, respectively. Inhibitory effect of the extracts on DNA gyrase was tested using gel-based DNA supercoiling assay. Among fifteen CHDs tested, methanol extracts of Lonicerae Japonicae Flos (S2), Taraxaci Herba (S7), Glycyrrhizae Radix et Rhizoma Praeparata cum Melle (S8) demonstrated an obvious inhibitory effect against supercoiling activity of DNA gyrase, and the others were either less active or could not be determined with the present method. Moreover, it was likely that S7 and S8 inhibit gyrase in a concentration-dependent manner. In conclusion, DNA supercoiling assay is a promising method to study the inhibitory activity of CHDs on bacterial DNA gyrase. Some CHDs do have gyrase-inhibitory activity as proposed. Further investigations are needed to elucidate the inhibition mechanism of these CHDs on supercoiling activity of gyrase.
Highlights
DNA supercoiling assay is a promising method to study the inhibitory activity of Chinese herbal drugs (CHDs) on bacterial DNA gyrase
Chinese herbal drugs (CHDs) and formulas have been used for thousands of years in China to treat a wide variety of diseases and nowadays receive more and more recognitions worldwide
At the concentration of 0.4 g/ml, methanol extracts of S2, S7, and S8 were most effective against supercoiling activity of gyrase, while those of S5 and S10 were less effective, and those of S3, S4, S9, S13 and S15 showed no obvious inhibitory effect on supercoiling activity of gyrase comparing with controls
Summary
Chinese herbal drugs (CHDs) and formulas have been used for thousands of years in China to treat a wide variety of diseases and nowadays receive more and more recognitions worldwide. Lonicerae Japonicae Flos had in vitro obvious antibacterial activity against Staphylococcus aureus, Escherichia coli, Shigella flexneri and Branhamella catarrhlissuch [3]. YINHUANG injection, which is prepared of Lonicerae Japonicae Flos and Scutellariae Radix and used for the treatment of tonsillitis, pharyngitis and upper respiratory tract infection in clinic, has been proven to has a good antibacterial effect on Staphylococcus, Pneu-. The clinically useful quinolone antibacterial drugs target DNA gyrase by trapping gyrase in an enzymedrug-DNA ternary complex and inhibiting its supercoiling activity, eventually inhibiting the growth of bacteria and killing them [10,11]. Are there any CHDs that possess anti-bacterial activities targeting bacterial DNA gyrases, either? We set out to conduct a comprehensive analysis of the inhibitory activity of methanol extracts of CHDs against bacterial DNA gyrase. The results, on one hand, will contribute to understanding of the antibacterial mechanism of CHDs; On the other hand, they may lead to development of novel therapeutic agents
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