An Investigation on the Antimicrobial Activity of Andrographis paniculata Extracts and Andrographolide in vitro

An aqueous and two ethanolic extracts of Andrographis paniculata, used in traditional Chinese, Thai and Indian medicine and andrographolide, an active principle of Andrographis paniculata, were investigated for their antimicrobial activity against nine bacterial species including Salmonella typhimurium, Escherichia coli, Shigella sonnei, Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae, Streptococcus pyogenes, Legionella pneumophila and Bordetella pertussis, using the disc diffusion method. Of all tested concentrations, direct antimicrobial activity of the two ethanolic Andrographis paniculata extracts was observed for only two human pathogens, Legionella pneumophila and Bordetella pertussis. However, no antibacterial activity of andrographolide against any of the pathogens tested in this investigation was observed. Given that the TLC of Andrographis paniculata extracts showed that andrographolide was present in all the three Andrographis paniculata extracts, it was concluded that the observed antimicrobial activity was due to other active principle(s) present in the extracts used in this investigation.