Isolation of antimicrobial compaunds from Andrographis paniculata (Burms F.) Nees (Hempedu bumi) /by Abubakar Sule

Abstract

In this study, non-polar (dichloromethane (DCM)) and polar (MeOH & aqueous) extracts of Andrographis paniculata Burms f.Nees (Hempedu bumi) whole plant were evaluated for in vitro antimicrobial activity against eight skin disease causing microbial strains (three Gram positive strains: Staphylococcus aureus (IMR S-277), Streptococcus pyogenes (IMR S-526) and Micrococcus luteus (IMR B-7); two gram negative strains: Proteus mirabilis (IMR P-74) and Pseudomonas aeruginosa (IMR P- 84) and three fungal strains: Trichophyton mentagrophytes (IMR T-44), Candida albicans (ATCC 90028) and Candida tropicalis (IMR C-353)) using the disc diffusion method at three different concentrations, viz., 1000, 500, and 250μg/ml, respectively. The extracts showed significant antimicrobial activities against both the Grampositive and Gram-negative bacteria as well as fungi strains tested. The antimicrobial activities ranged from 7.00 ± 0.50-19.67 ± 0.76mm on the tested microbial strains whereas MIC and MBC/MFC values ranged from 100-250μg /ml and 250-400μg /ml, respectively. Time-kill experiments indicated that A. paniculata extracts were bactericidal against Gram positive bacteria whereas bacteriostatic and fungistatic against Gram negative bacterial and fungal strains. Bioassay guided isolation of the DCM and MeOH extracts of A. paniculata afforded three antimicrobial compounds viz., 3-O-β-glycosyl-14-deoxyandrographolide, 14-deoxyandrographolide and 14- deoxy-11, 12-didehydroandrographolide. Their structures were established through 1H-MNR, 13C-MNR, UV, IR spectra and direct comparison with previously reported data of similar compounds. Our findings support its traditional claims and form a strong basis for the exploration of A. paniculata’s antimicrobial potential to treat skin frailties efficaciously.