Taraxacum mongolicum extract exhibits antimicrobial activity against respiratory tract bacterial strains in vitro and in neonatal rats by enhancing systemic Th1 immunity

Purpose: To study the antimicrobial activity of the Taraxacum mongolicum extract against respiratory infection-causing bacterial strains in vitro and in neonatal rats. Methods: The in vitro antibacterial activity was assessed by micro-dilution method. Antioxidant activity was determined by ferric reducing antioxidant power (FRAP), nitro blue tetrazolium (NBT) and 2, 2diphenyl-1-picrylhydrazyl (DPPH) assays. In vivo antimicrobial activity was evaluated in neonatal rat model. Interleukin (IL)-2 (IL-2) and gamma interferon (IFN-gamma) were estimated using enzyme-linked immunosorbent assay (ELISA). Results: The hydro-methanol extract of T. mongolicum contained high levels of phenolics and flavonoids, and exhibited strong antimicrobial activity against respiratory infection-causing bacterial species with MICs of 25 -100 mu g/ml, and MBCs of 55 -215 mu g/ml. The highest and lowest antimicrobial activities were observed against Streptococcus pneumonia and Haemophilus influenza, respectively. The extract at doses of 25 and 50 mg/kg exerted protective effects against Streptococcus pneumonia-infected neonatal rats by boosting their Th1 immunity. It enhanced the production of interleukin (IL)-2, concomitant with decreased production of interferon (IFN)-gamma in neonatal rats. The extract contained isoetin, hesperidin, naringenin, kaempferol, sinapinic and gallic acid. Conclusion: These results suggest that the hydro-methanolic extract of Taraxacum mongolicum and its constituents can be potentially developed for use in the management of respiratory bacterial infections.