Chemical composition and antimicrobial activities of Urena lobata L. (Malvaceae)

Abstract

The chemical composition and antimicrobial activity of the leaves of Urena lobata L. were investigated. The proximate analysis showed that the leaves contained moisture (7.21%), crude fibre (6.31%), carbohydrate (47.53%), crude protein (19.79%), fat (10.21%) and ash (8.95%). The mineral analysis in mg/100 g indicated that the leaves contained calcium (42.09), copper (0.31), iron (9.35), magnesium (35.38), manganese (0.81), phosphorus (24.91), potassium (35.38), sodium (29.48) and zinc (51.55). The phytochemicals detected in the leaves of U. lobata L. were alkaloids, cardiac glycoside, tannins, terpenoid and saponin;while flaonoid, phlobatanin and steroid were not detected. Antibacterial activities of the leaf extract showed that Escherichia coli was sensitive to the methanolic extract of the plant and had a zone of inhibition that varied from 1 - 4 mm with concentration that varied from 6.25 - 50 mg/ml. Staphylococcus aureus had zone of inhibition that varied from 1.0 - 3.0 mm,Enterococcus spp. had zone of inhibition that varied form 1.0 - 2.0 mm with concentration that varied between 25 - 50 mg/ml respectively. Klebsiella spp. had a zone of inhibition of 2.0 mm at 50 mg/ml concentration, while Pseudomonas aeruginosa was resistant to the extract at all the concentrations tested. The effect of methanolic extract of U. lobata L on radial mycelial growth of the test fungi revealed that Botryodiplodia theobromae had a percentage inhibition which varied from 20 - 50% with concentration of 6.25 - 50 mg/ml, however, B.theobromae was not sensitive at 3.13 mg/ml. However, Rhizopus spp. had a percentage inhibition that varied from 20 - 50% with concentration that varied from 12.5 - 50 mg/ml. Key words: Chemical composition, phytochemical analysis, antimicrobial activities, Urena lobata L.