In vitro Antibacterial Activity of Plants Used as Herbal Tea in Tanzania

Aim: This study was to evaluate antibacterial activity of Rhus vulgaris, Sphaeranthus bullatus, Osyris lanceolata, Ocimum gratissimum, Cymbopogon citratus, Acacia nilotica and Tylosema fassoglensis plants used as herbal teas in Tanzania and antibacterial synergic effect when combined with Cymbopogon citratus.

Study Design: In vitro antibacterial assay was employed to determine Minimum Inhibitory Concentration (MIC).

Methodology: Pulverized plant materials were sequentially extracted using dichloromethane, ethyl acetate and distilled water. Minimum Inhibitory concentration (MIC) was measured for antibacterial activity against gram negative bacteria using 96-well micro dilution method.

Results: The highest antibacterial activity with MIC value of 0.19 mg/mL was exhibited by Camellia sinensis against Salmonella typhi. About 3.7% of the extract exhibited antibacterial activity with MIC value of 0.3906 mg/mL whilst the remaining extract exhibited antibacterial activity with MIC values ranging from 0.781 to 25 mg/mL against Escherichia coli, Pseudomonas aeruginosa, Salmonella kisarawe, Klebsiella pneumoniae, Salmonella typhi, Proteus mirabilis and Klebsiella oxytoca. Thirty percent of the tested extracts exhibited antibacterial activity with MIC values below 1 mg/mL indicating that they are potential antibacterial drug leads according to Rios and Recio (2005). The antibacterial activity of combined extracts of C. citratus and herbal teas revealed both antibacterial synergic and antagonistic effects.

Conclusion: The current study established that herbal teas can be consumed not only as refreshment but also as a remedy for Gram negative bacterial infections. It is therefore recommended that when herbal tea is consumed as a remedy, incorporation of C. citratus should only be necessary when it induces synergistic effects.