SCREENING ETHANOLIC AND AQUEOUS LEAF EXTRACTS OF TARAXACUM OFFINALE FOR IN VITRO BACTERIA GROWTH INHIBITION

Abstract

The increased incidence of bacteria resistance to many antibacterial drugs is of great concern and medicinal plants have proven as an alternative source of antibacterial agents. Taraxacum officinale is a stemless herb used as food vegetable and medicine. The plant is found chiefly as a persistent weed in many temperate regions. Previous reports show that the leaves of T. officinale contain bioactive components. In the current research, the ethanolic and aqueous leaf extracts of T. officinale were screened for phytochemicals and in vitro antibacterial activity. Escherichia coli, Klebsiella pneumoneae, Pseudomonas auregenosa and Staphylococcus aureus were used as test organisms. Data was analyzed using Mann-Whitney U-test and P values less than 0.05 were considered significant. Preliminary phytochemical screening of aqueous and ethanolic leaf extract of T. officinale revealed the presence of saponins, phenolics, triterpenes tannins, phytosteroids and reducing sugar some of which have been reported to be bioactive. The bacterial growth inhibition activity of the extracts was evaluated using agar well diffusion method at concentrations ranging from 50mg/ml to 200mg/ml. At concentration 200mg/ml, the ethanolic leaf extract showed inhibition against only E. coli and S. aureus with mean diameter of zone of inhibition of 23.50±1.00 mm and 10.75±1.50 mm respectively. At concentration 100mg/ml, the mean diameter zone of inhibition for the ethanolic extract were 16.00±2.83 mm and 9.00±0.82 mm against E. coli and S. aureus respectively. At concentration 50mg/ml, the ethanolic leaf extract showed inhibition against only E. coli with mean diameter of the zone of inhibition of 10.50±1.00 mm. The aqueous extract on the other hand showed inhibition against E. coli only at 200mg/ml and 100mg/ml. The result reveals that antibacterial activities of aqueous and ethanolic leaf extract of T. officinale were concentration dependent. The result further suggests that the ethanolic extract of T. officinale was the most active compared with the aqueous extract. Of the bacteria tested, E. coli was the most susceptible to the extracts. In conclusion, both aqueous and ethanolic extract of T. officinale possess significant (P < 0.05) antibacterial activity and may be very useful in the discovery of novel antibacterial agents.