In vitro Antimicrobial Activity of Agents from Spilanthes filicaulis and Laportea ovalifolia against Some Drug Resistant Bacteria

Abstract

Aims: In a search for natural substances with potential for the treatment of typhoid fevers and urinary tract infections (UTI), extracts and compounds obtained from S. filicaulis and L. ovalifolia were tested for antibacterial activity. Study Design: Extraction, fractionation, isolation and identification of compounds, antibacterial evaluation. Place and Duration of Study: University of Buea and University of Dschang, Cameroon, between February 2012 and December 2013. Methodology: The most active extracts were fractionated by column and thin layer chromatographic (TLC) techniques, and tested for antibacterial activity, using agar diffusion and broth dilution methods. The structures of pure compounds obtained were elucidated by NMR spectroscopy, physical data and by comparing these values with published data. Results: Methylene chloride extract of S. filicaulis was the most active (diameters of 12-15 mm). Methylene chloride (12-16 mm) and methanol (13-16 mm) extracts of L. ovalifolia were active against all isolates. MIC values ranged from 0.08-1.25 mg/ml for the fractions of S. filicaulis and 0.16-1.25 mg/mL for L. ovalifolia fractions. Streptococcus sp. was the most sensitive microbial agent (MIC=0.08 mg/mL) for fraction IS of S. filicaulis. Staphylococcus aureus and Streptococcus sp. recorded the lowest MIC for fraction ML of L. ovalifolia. Two compounds isolated from S. filicaulis were identified as beta -stigmasterol (1) and hexadecanoic acid (2) while one from L. ovalifolia was identified as beta -sitosterol (3). These three compounds and two other secondary metabolites not yet identified (GL2 and GL3) showed antibacterial activity. The in vitro activity of beta -stigmasterol against Klebsiella pneumoniae and Salmonella Typhimurium is reported herein for the first time. Conclusion: These plants may contain lead molecules for the formulation of drugs useful for the management of UTI and typhoid fevers caused by resistant pathogens.