Antimicrobial activity of stigmasterol from the stem bark of Neocarya macrophylla

Abstract

Background: Natural products play a significant role in human therapy. They represent a huge reservoir of bioactive chemical diversity and help in understanding the cellular pathways that are essential component of drug discovery process. Objective: This study was aimed at evaluating the antimicrobial activity of stigmasterol isolated from the stem bark of Neocarya macrophylla. Methods: Stigmasterol previously isolated from the stem bark of N. macrophylla was subjected to antimicrobial screening against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), S. aureus, Streptococcus faecalis, Escherichia coli, Salmonella typhimurium, Pseudomonas fluorescens, Klebsiella pneumoniae, Candida albicans and Candida krusei using agar diffusion and broth dilution methods. Results: Susceptibility test results showed that the compound (100 μg/mL) inhibited the growth of all the test organisms with mean zone of inhibition range from 23 mm to 30 mm except the VRE, S. typhi and K. pneumoniae. The activity of stigmasterol was compared with that of ciprofloxacin (5 μg/mL), the standard antibacterial drug, and fluconazole (5 μg/mL), the antifungal agent. The test compound displayed a broad-spectrum of activity, and in many cases exhibited comparable antibacterial activity when compared to ciprofloxacin. Interestingly, the compound also showed antifungal activity against Candida spp., affording comparable inhibitory effect as fluconazole. The minimum inhibitory concentration (MIC) and the minimum bactericidal/fungicidal concentration (MBC/MFC) of stigmasterol range from 6.25 μg/mL to 25 μg/mL and from 12.5 μg/mL to 50 μg/mL, respectively. Conclusion: These properties suggest that the isolated stigmasterol is a potent and broad-spectrum antibacterial and antifungal agent and as such may serve as a lead compound in the development of novel antimicrobial drugs.