Antibacterial Potential and Safety Level of Euphorbia tirucalli and Vernonia glabra Commonly used by Residents in Iringa, Tanzania

This study was conducted to evaluate the antibacterial potential of Euphorbia tirucalli L. and Vernonia glabra (Steetz) Vatke and their safety level.  The plants were obtained from Kiwere ward in the Iringa district, prepared and extracted in aqueous and ethanol solvents. The E. tirucalli and V. glabra plant extracts were studied for their antimicrobial activities against E. coli isolates and E. coli ATCC ۲۵۹۲۲ using the agar well diffusion method. Minimum inhibitory and bactericidal concentrations (MIC and MBC) were determined. Among the tested plant extracts, the ethanol extracts of V. glabra showed the highest activity against E. coli isolates and E. coli ۲۵۹۲۲ with a mean inhibition zone of ۱۷.۹۰۹±۰.۳۲۹۷ and ۲۲.۵ ± ۰.۵۰۰ respectively. Furthermore, on MIC and MBC, the ethanol extracts of V. glabra had a better activity with the values ranging from ۱.۲۵-۲.۵ mg/ml and ۲.۵-۵ mg/ml respectively compared to other plant extracts. Phytochemical screening revealed the extract’s presence of alkaloids, flavonoids, tannins, saponins, triterpenes and steroids. The brine shrimp lethality test showed that the aqueous extract of E. tirucalli was non-toxic with LC۵۰ of ۱۰۰۷ µg/mL, while ethanol extract of E. tirucalli, aqueous extract of V. glabra and ethanol extract of V. glabra were less toxic with LC۵۰ values of ۵۸۹, ۵۰۷ and ۶۵۸ µg/mL respectively.  These results indicate that the plant extracts have bioactive constituents that could be accounted for their pharmacological properties. Furthermore, these results proved the claim of indigenous people in the study area on the effectiveness and safety of the plants and supported the use of these plant species in traditional medicine.

Keywords:

Antibacterial activity , Euphorbia Tirucalli , Vernonia Glabra , Escherichia coli , Phytochemical screening , Brine Shrimp Lethality Test