Antibacterial Activity of the Bioactive Fractions of Cyathula uncinulata (Amaranthaceae)
M. A. Bisi-Johnson *
Department of Medical Microbiology, Walter Sisulu University, Mthatha 5117, South Africa and Department of Microbiology, Obafemi Awolowo University, Ile-Ife, Nigeria
C. L. Obi
Directorates of Academic Affairs, University of Fort Hare, Alice 5700, South Africa
T. Hattori
Department of Emerging Infectious Diseases, School of Medicine, Postgraduate Division, Tohoku University, Sendai, Japan
Y. Oshima
Department of Natural Products Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
B. B. Samuel
Department of Paraclinical Science, Phytomedicine Programme, Faculty of Veterinary Medicine, University of Pretoria, Onderstepoort 0110, South Africa
J. N. Eloff
Department of Paraclinical Science, Phytomedicine Programme, Faculty of Veterinary Medicine, University of Pretoria, Onderstepoort 0110, South Africa
*Author to whom correspondence should be addressed.
Abstract
Cyathula uncinulata (Schrad.) Schinz is used in ethnomedicine in various parts of the world. This study isolated and characterized a bioactive compound from C. uncinulata based on its antibacterial activities. Separation of the bioactive compound from the ethyl acetate fractions of the plant was by solvent-solvent fractionation followed by repeated column chromatography. The structure of the compound was elucidated by nuclear magnetic resonance and mass spectroscopic methods. The NMR spectra of the isolated compound showed that the compound with formula C22H38O7 and molecular weight 414.5329 has a long aliphatic chain made up of sugar and fatty acyl moiety. The minimum inhibitory concentration (MIC) of fractions of extracts ranges from 0.39 to 2.5 mg/ml. The MIC of the final purified compound was 0.34 mg/ml compared to the MIC of 0.19 of kanamycin indicating a reasonable bioactivity. This study thus supports the traditional use of C. uncinulata in the treatment of bacterial infections.
Keywords: Cyathula uncinulata, bioactive compound, spectroscopy, minimum inhibitory concentration