Stigmasterol and β-Sitosterol: Antimicrobial Compounds in the Leaves of Icacina trichantha identified by GC–MS

Abstract

Abstract Background The development of resistance to many antibiotics currently in use has necessitated the search for more effective alternatives. Plants have been used in ethnomedicine in different parts of the world to treat various diseases. Many studies on plants have confirmed their medicinal potentials and have led to the isolation and characterization of several potential drug candidates. This study investigates the leaves of Icacina trichantha for antimicrobial properties and seeks to identify the compounds responsible for the observed activities. The leaves of Icacina trichantha are used in ethnomedicine for the treatment of skin infections. In this study, a solvent-based fractionation of bioactive compounds in the leaves of Icacina trichantha was carried out using hexane, ethyl acetate, and methanol. The resultant extracts were screened for antimicrobial activity against six bacteria and four fungi using standard procedures. GC–MS analysis of the most active fraction was carried out. Results The non-polar fraction (hexane) showed better antimicrobial activity than the ethyl acetate and methanol extracts. At 200 mg/mL, the fraction showed inhibition of 28.0 ± 0.82, 23.7 ± 0.47, and 24.6 ± 0.94 against Staphylococcus aureus, Escherichia coli, and Bacillus subtilis,, respectively. At the same concentration, the extract showed zones of inhibition of 18.0 ± 0.82 against Candida albicans and Penicillium notatum. The lowest Minimum Inhibitory Concentrations (MIC) values of 2.5 mg/mL were obtained against Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. GC–MS analysis of the hexane extract revealed 62 peaks, out of which ten peaks were successfully characterized. Conclusions None of the extracts screened for antibacterial and antifungal activities in this study is as potent as the standard drugs, Gentamicin and Tioconazole. The hexane extract, however, showed some activity against the microorganisms and was analyzed using GC–MS. The hexane extract contained many bioactive compounds, some of which could not be identified. Two of the identified compounds, Stigmasterol and β-Sitosterol, are known to possess antimicrobial properties. However, the unidentified compounds could also have contributed significantly to the antimicrobial activities of the extract.