Phytochemical analysis and antibacterial activity of leaf and stem bark extracts of Citrus sinensis (sweet orange)

Background and objective: Resistance of microorganisms to chemical agents is a challenge in the treatment of various infections. Therefore, there is a need to find new substances with efficient antimicrobial potential. The aim of this study was to determine phytochemical composition and antimicrobial activity of Citrus sinensis extract obtained from its leaf and bark. Materials and methods: Leaves and stem barks of Citrus sinensis were collected from University of Agriculture, Makurdi, Benue State, Nigeria. Bacterial isolates of Escherichia coli, Salmonella typhi, and Staphylococcus aureus were prepared in the microbiology laboratory. The leaves and stem barks were extracted with ethanol and water using maceration technique. Agar well diffusion method was used to determine antibacterial activity of the extracts. Broth dilution method was used to determine minimum inhibitory concentration (MIC) of the extracts. Minimum bactericidal concentration test was done by culturing the MIC positive broth on nutrient agar plates. Steroids, phenols, flavonoids, saponins, alkaloids, tannins, and glycosides were determined according to standard methods in the laboratory. Results and conclusion: Phytochemical screening showed the presence of phenols, flavonoids, alkaloids, tannins, steroids, and glycosides. Ethanolic leaf extract had the highest antibacterial activity against S. typhi with inhibition diameter of ۲۵ mm, followed by ۲۰ mm for E. coli and ۱۲ mm for S. aureus. In comparison, ethanolic stem bark extract showed the highest inhibition against E. coli with diameter inhibition of ۲۵ mm, while diameter inhibition of ۲۲ mm and ۲۰ mm were determined for S. aureus and S. typhi, respectively. Aqueous extract of leaf showed inhibition zone of ۱۶ mm for S. typhi, and ۱۰ mm for E. coli and S. aureus. Inhibition zone of ۱۶, ۱۱, and ۱۰ mm was observed for S. typhi, E. coli, and S. aureus respectively, after treatment by aqueous extract of stem bark. Minimum inhibitory concentration and minimum bactericidal concentration of both extracts were in the range of ۶.۲۵-۵۰.۰۰ mg/ml. This study revealed that the leaf and stem bark of Citrus sinensis contain several bioactive compounds with antibacterial potential (i.e., steroids, phenols, flavonoids, saponins, alkaloids, tannins, and glycosides) which can be used for treatment of microbial infections.

Keywords:

antibacterial , Citrus sinensis , Minimum bactericidal concentration , Minimum inhibitory concen-tration , Phytochemical