Anti-bacterial activity and characterization of compounds from the leaf extract of Solenostemon Latifolius Hochst.ex benth.

Abstract

Infectious diseases have continuously been reported among the leading causes of death in the world. These include bacterial infections like tuberculosis and pneumonia. Several antibiotics have been used against these infections. However, bacteria are becoming resistant to a number of antibiotics, leading to increased mortality, morbidity and treatment costs. Therefore, there is need to discover more effective antibacterial drugs and plants have been sought as sources of antibiotics. The aim of this study was to isolate and identify antibacterial compounds from Solenostemon latifolius, a plant that is locally used to treat bacterial infections in Uganda. The plant sample was collected, dried and ground into a fine powder. The powder was extracted using distilled water and 1:1 DCM -methanol mixture. Phytochemical screening was done and both extracts and isolated compounds were subjected to antibacterial test using the agar well diffusion method. The organic extract was then partitioned and subjected to isolation using a column packed with silica gel. Structural elucidation of the isolated compounds was done using NMR, MS and UV spectroscopy. Phytochemical screening revealed presence of flavonoids, terpenoids and steroids among others. The zone of inhibition (ZOI) for the organic extract was 14 mm and 18 mm against Staphylococcus aureus and Escherichia coli. The aqueous extract had ZOI as 13 mm for E. coli. S. aureus was not susceptible to the aqueous extract. Isolated compounds were identified as Coleone U, β-sitosterol, stigmasterol and 3,4-dihydroxyphenyl caffeate. Coleone U (ZOI between 10-12 mm at a concentration of 40 mg/ml) had activity comparable to that of gentamicin standard used. Therefore, Solenostemon latifolius is a medicinal plant with several classes of phytochemicals responsible for its antibacterial activity. This supports its use as a medicinal plant against bacterial infections