Phytochemical analysis, antimicrobial and antioxidant activities of leaf extract of Vernonia tigna Klatt (Asteraceae)

The aim of this study was to determine the phytochemical composition, antimicrobial and antioxidant activities of Vernonia tigna leaf extracts used in folk medicine and to validate its therapeutic claim. Powdered plant material from Vernonia tigna was extracted by microwave-assisted extraction using n-hexane, chloroform, ethyl acetate and methanol and subjected to phytochemical screening using standard methods. The antimicrobial activity was determined by agar diffusion method as outlined by the NCCLS. The Free radical scavenging activity was determined by the DPPH method. The phytochemical screening of the crude extract revealed the presence of tannins, saponins, flavonoids, and alkaloids. The antimicrobial activity was determined by minimum inhibitory concentration (MIC) against four bacterial strains (S. aureus, B. subtilis, E. coli and P. aeruginosa). The result showed moderate inhibition against bacterial strains. The values of the minimum inhibitory concentration (MIC) ranged from 1.25 – 3.125 mg/mL for all the organisms studied. The radical scavenging activity of the extracts showed significant inhibition at different concentrations of 50 – 250 µg/mL. All the microbes were inhibited to varying degrees. The results of this study give credence to the ethno-medicinal use of Vernonia tigna.