Antibacterial activity of the leaves of Phyllanthus discoideus

The lyophilized aqueous extract (LWE) from the leaves of Phyllanthus discoideus was found to show an antibacterial activity. The alkaloid fraction obtained from LWE inhibited the growth of Escherichia coli and Enterococcus faecium (MIC = 1.6 mg/ml), Pseudomonas aeruginosa (MIC = 0.78 mg/ml), Staphylococcus aureus and Mycobacterium smegmatis (MIC = 0.2 mg/ml). Among the alkaloids identified, viroallosecurinine and securinine showed a high activity. Viroallosecurinine exhibited a MIC of 0.48 micrograms/ml for Ps. aeruginosa and Staph. aureus. This alkaloid is bactericidal since the yields of MIC/MBC were less than 1. The MIC of securinine was 0.500 mg/ml for E. coli, Staph. aureus and Myc. smegmatis. These effects of Phyllanthus discoideus leaf extracts support some of the local uses of the plant in traditional therapy.