Phytochemical screening and antimicrobial activity of Picrorrhiza kurroa, an Indian traditional plant used to treat chronic diarrhea

Phytochemical screening of the rhizomes of Picrorrhiza kurroa Benth revealed the presence of some bioactive components, which have been linked to antimicrobial properties. Various chemical tests and TLC studies showed the presence of glycosides, sterols and phenolic compounds when tested on different extracts of P. kurroa rhizomes. The major chemical constituents found in this plant were iridoid glycosides and cucurbitacins (triterpenoids) present in the methanolic extract. The effects of methanolic and aqueous extracts on some pathogenic bacterial and fungal strains viz.: Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Escherichia coli and Candida albicans, Aspergillus niger, respectively, showed that the plant part can be used to treat infections caused by these bacteria and fungi. The aqueous and methanolic extracts showed antibacterial activity but the significant antimicrobial activity was shown by methanolic extract only, against P. aeruginosa and S. aureus; while moderate activity against E. coli, B. subtilis and M. luteus. The effectiveness of the crude extract confirmed its use in traditional medicine to treat skin, urinary tract, diarrheal infections and gastrointestinal infections. The aqueous extract was less effective against the microbial strains and no activity against fungal strains. The MICs of the methanolic extract against the test bacteria were high and correlate with sensitivity test results. The effectiveness of the extracts was less than the conventional antibiotic, ciprofloxacin. Further the HPTLC studies were performed to estimate the content of iridoids and it was found to be 3.66 ± 0.11 and 4.44 ± 0.02 for picroside I and kutkoside, respectively.