Sequential extraction using a cold maceration method and column chromatographic separation of the roots Kniphofia insignis headed to the isolation of three anthraquinones: one monomeric anthraquinone (1) and two dimeric anthraquinones (2 and 3). It was further purified by Sephadex LH-20 and recrystallized. The structures of these compounds were established based on the spectroscopic analyses including NMR (1H-NMR and 13C-NMR and infrared) and comparison with reported literatures. In an in vitro antimicrobial assay of the crude extracts, the isolated compounds were made against four bacterial strains (S. aureus ATCC 25923, B. subtilis ATCC 6633, E. coli ATCC 35218, and P. aeruginosa ATCC 27853) and Fusarium spp. fungal strain. In the crude extracts of chloroform, substantial antimicrobial activity was seen with the highest activity against B. subtilis (16 mm) and E. coli (22 mm). Meanwhile, compound 1 has a better zone of inhibition with 14 mm against P. aeruginosa, whereas compound 2 showed better activity (13 mm) against Fusarium spp. fungal strain.

Sequential extraction of the roots of Kniphofia insignis using cold maceration techniques and column chromatographic separation leads to the isolation of one monomeric anthraquinone, chrysophanol (1). The structure of the compound was established using spectroscopic analyses including NMR (1H and 13C-NMR, infrared) and comparison with reported literature. The in vitro antibacterial activities of the crude extracts and the isolated compounds were evaluated against four bacterial strains (S. aureus ATCC 25923, B. subtilis ATCC 6633, E. coli ATCC 35218, and P. aeruginosa ATCC 27853). Among them, the crude extract, acetone extract, has shown substantial antibacterial activity with the highest activity against E. coli (22.3 mm). However, compound 1 has a better zone of inhibition with 19.3 mm against P. aeruginosa.