Investigation of Total Phenolic and Flavonoid Contents, and Evaluation of Antimicrobial and Antioxidant Activities from Baeckea frutescens Extracts

Baeckea frutescens L. is a medicinal plant endemic to the tropical area and it has been used by locals for topical and oral ailments. This study investigated total phenolic and flavonoid contents and also evaluated in vitro antimicrobial and antioxidant activities of of Baeckea frutescens crude extracts. These extracts were assessed for their antibacterial activities against strains of Escherichia coli, Staphylococcus aureus, Salmonella thypii, and Pseudomonas aureginosa by the broth micro-dilution methods using a modified tetrazolium-based colorimetric assay (3-(4, 5-dimethylthiazol)-2, 5-diphenyl tetrazolium bromide (MTT) assay). Baeckea frutescens crude extracts were also tested against the stable DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free-radical. The results indicated that Baeckea frutescens water and ethanol extracts possesed remarkable antibacterial activity with the minimum inhibitory concentration less than 100 mu g/ml against Escherichia coli and Salmonella thypi. On the evaluation of the antioxidant activity via DPPH assay, Baeckea frutescens ethanol extracts exhibited a good antioxidant activity with IC50 less than 50 mu g/ml and Baeckea frutescens water extracts showed a moderate antioxidant activity with IC50 less than 100 mu g/ml.