Phytochemical and antibacterial studies of Indigofera secundiflora

The genus Indigofera comprises about 700 species that are distributed geographically in tropical regions including Nigeria, Burkina Faso and India [1]. Various species of Indigofera have been used in folkloric medicine, which include antibacterial, antifungal, antisnake venom properties and for tumors in particular the decoction of the aerial parts of Indigofera secundiflora is used against bacterial infections, diarrhea and as a cough remedy [2]. In continuation of our phytochemical work into Indigofera species of Nigeria flora, the aerial parts of Indigofera secundiflora were investigated. The acetone extract was screened for anti-bacterial activity against E. coli, B. subtilis, P. aeruginosa and S. aureus at concentrations of 5 and 10mg/ml. The extract inhibits all the test organisms with zones of inhibition ranging from 13 to 23mm comparable to standard antibiotics gentamycin 10µg/ml and ciprofloxacin 10µg/ml. Fractionation of this extract over silica gel open column chromatography, gel filtration over Sephadex LH-20 and preparative TLC gave quercetin, quercetin3-methyl ether, quercetin 3,4-dimethyl ether and kaempferol-3-methyl ether. The structures were elucidated using NMR techniques and compared with those reported in literature [3,4]. The anti-bacterial activity of the isolated flavonoids is discussed.

References: [1] Dalziel, J.M. (1965) The useful plants of West tropical Africa. A Crown agent for oversea publication.

[2] Bakasso, S. et al. (2008) Pakistan J. Biol. Sci. 11:1429–1435.

[3] Mabry, T.J., Markham, K.R. (1968) Systematic Identification of Flavonoids. Springer Verlag, Berlin.

[4] Agrawal, P.K (1989) Carbon-13NMR of Flavonoids. Elsevier science, Amsterdam.