Exploring Plumbagin as a Potential Phytochemical to Combat Multidrug Resistance in Bacterial Strains

The clinical efficacy of existing antibiotics is threatened by the emergence of multidrug-resistant pathogens. In India, traditional herbal medicine has attracted much of the scientific interest and increasing continuously. This study evaluates the antimicrobial activity of crude plumbagin extract (CRPB) from Plumbago auriculata and standard plumbagin (PB) (which is a 98% pure compound from Sigma Aldrich, USA) against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae, Citrobactor, and their MDR strains with disc diffusion assay and minimum inhibitory concentration (MIC). PB was extracted from leaves of P. auriculata and verified by spectrophotometric and high-performance liquid chromatography (HPLC) analysis. Standard PB showed the lowest MIC against S. aureus ATCC and its MDR strains B48 and F204 at 64 µg/mL. Although E. coli ATCC had an MIC at 128 µg/mL, and it's MDR U1815, P1189 at 256 µg/mL. K. pneumoniae ATCC and its MDR showed a higher MIC at 128 µg/mL. CRPB showed MIC against S. aureus ATCC (256 µg/mL), B48 (256 µg/mL), and F204 (512 µg/mL). P. aeruginosa ATCC, E. coli ATCC and their MDR strains, and K. pneumoniae ATCC and its MDR P290 were resistant at all the concentrations for CRPB. CRPB showed relatively specific antimicrobial activity, and naphthoquinone compound PB could be mainly responsible for its activity. In the disc diffusion assay, compared to standard streptomycin, CRPB exhibited good activity against S. aureus ATCC (31 mm) and MDR B48 (37 mm), E. coli MDR P1189 (18 mm), and Citrobactor MDR F182 (22 mm). Growth of S. aureus was completely inhibited. PB can be developed as a potential drug candidate after further purification.