Phytochemical screening and antibacterial activity of methanolic leaf extract of Coleus aromaticus benth

Abstract

In the present study, the aqueous extracts of seven plants such as Cassia auriculata L., Coleus aromaticus Benth, Lawsonia inermis L., Mimosa pudica L., Phyllanthus niruri L., Tinospora cordifolia Miers., and Tribulus terrestris L., were screened for their antibacterial activity against human pathogenic bacteria like Escherichia coli, Haemophilus influenzae, Klebsiella pnuemoniae, Proteus mirabilis, Salmonella typhi, Shigella flexneri and Staphylococcus aureus. The antibacterial assay was performed by the agar-well diffusion method. Coleus aromaticus, whose aqueous extract recorded antibacterial activity at 10 mg/ml, was subjected to methanol extraction and tested for the presence of phytochemical compounds and also for antibacterial activity at different concentrations viz., 0.25 mg/ml, 0.5 mg/ml, 1.0 mg/ml, 2 mg/ml, 4 mg/ml, 6 mg/ml, 8 mg/ml, and 10 mg/ml. Preliminary phytochemical analysis of the leaves extract revealed the presence of reducing sugar, protein, phenolic compounds, alkaloids, flavonoids, tannins, cardiac glycosides, steroids, and terpenoids. Methanolic leaf extract of C. aromaticus showed moderate to high activity against all the investigated bacterial pathogens. The results indicated that the methanolic leaf extract of C. aromaticus is pharmacologically active and is a good antibacterial agent. Further investigations are required on isolation and characterization of the bioactive principle responsible for antibacterial activity.