Phytochemical investigation of roots of kniphofia insignis and evaluation of its antimicrobial activities

Abstract

Kniphofia is a medicinal plant that is commonly used for treatment of different ailments including menstrual pains, infertility, abdominal cramps, wounds, malaria, chest complaint, gonorrhea and hepatitis B. in Ethiopia. Therefore, the aim of this study was to isolate, characterize and evaluate antimicrobial activities of the crude extract and compounds from the root of Kniphofia insignis. Meanwhile the root part of the plant was air dried, grinded and subjected to sequential extraction using n-hexane, chloroform, acetone and methanol by cold maceration method resulted 10.0(1%), 27.5(2.75%), 17.0(1.7%) and 45.0 (4.5%) g crude extract of each. The concentrated crude extracts were evaluated for their antibacterial and antifungal activities against four bacterial strains (Escherichia coli, Staphylococcus auraus, Bacillus subtilus and Pseudomonas aeruginosa) and one fungus strain (Fusarium spp) and the extract with the better activity was then subjected to further purification by column chromatography on silica gel. It results three compounds; a monomeric anthraquinone (1) and two dimeric anthraquinones (2 & 3). The structures of these isolated compounds were characterized by NMR and IR spectroscopy techniques. The isolated compounds were also evaluated for their in vitro antimicrobial activity as described above. The compounds exhibited marginal activity against the bacterial strains with the highest activity observed for compound 1 with diameter of inhibition (14 mm) against P. aeruginosa. Whereas compound 2 showed better activity (13 mm) against fusarium spp fungal strain which supports the validity of the plant used traditionally as a medicine.