Antibacterial properties and GC-MS analysis of ethyl acetate extracts of Xerophyta spekei (Baker) and Grewia tembensis (Fresen)

Conventional antibiotics are associated with various side-effects. Therefore, there is need of using plant-derived antibiotics with fewer side-effects. Grewia tembensis and Xerophyta spekei, which have been extensively utilized in the Mbeere community, were studied to support their folkloric use and demonstrate their antibacterial capabilities. Salmonella Typhi ATCC 1408, Bacillus subtilis ATCC 21332, Staphylococcus aureus ATCC 25923, and Escherichia coli ATCC 25922 were all used in this study. As a standard reference, Ciprofloxacin (100 μg/ml) was employed, and 5% DMSO was used as a negative reference. Tests for antibacterial activities included disc diffusion, minimum inhibitory concentrations, and bactericidal concentrations. G. tembensis exhibited effects on S. aureus only with Mean Zone Inhibition (MZI) of 07.07 ± 0.07 to 12.33 ± 0.33 mm and 08.33 ± 0.33 to 11.67 ± 0.33 mm for stem bark and leaf extracts respectively. While X. spekei extract had effects on S. aureus with MZI of 07.67 ± 0.33 to 14.67 ± 0.33 mm and B. subtilis with MZI of 09.67 ± 0.33 to 14.33 ± 0.33 mm. Ciprofloxacin demonstrated significantly higher activities as compared to the plant extracts in all the concentrations (p < 0.05), while 5% DMSO had no activity. GC-MS analysis demonstrated the availability of compounds with known antibacterial effects. Therefore, the current study recommends ethnomedicinal and therapeutic use of G. tembensis and X. spekei as antibacterial agents.