Browsing by Subject "ohutlevykromatografia"

The increasing microbial resistance against conventionally used antibiotics has become a worldwide problem. Plant derived compounds may have different mechanisms of action, which might reduce the resistance problem. The aim of this study was to investigate the antimicrobial activity of three African medicinal plants, Terminalia kaiserana, Terminalia sambesiaca and Combretum psidioides, belonging to the family Combretaceae. All three plant species are used for treatment of bacterial and fungal infections in African traditional medicine, but there is limited, or in the case of Terminalia kaiserana, no research on the chemical composition of these plants. Dried plant material was extracted with methanol and solvent-partition extraction was performed using chloroform, butanol and water. Chemical compositions of the fractions was examined using RP-18 thin layer chromatography. The fractions were screened for antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa using an agar diffusion method. The most effective fraction against both bacteria was the water soluble fraction of the root bark of T. sambesiaca. A microdilution method was used to determine minimum inhibitory concentration (MIC). This method was used for S. aureus, P. aeruginosa and in addition for Mycobacterium smegmatis. The method was modified for M. smegmatis to contain a smaller inoculum size in the beginning of the experiment than for the two other bacteria. The lowest MIC-values against S. aureus were given by the crude extract and water soluble fraction of the stem bark of C. psidioides and by the butanol fraction of the same plant against P. aeruginosa. The results on the antibacterial effects of the screened extracts were notable and significant. The antimicrobial activity against M. smegmatis was not as obvious as for the other tested bacteria but the choloroform fraction of the root bark of T. kaiserana and the butanol fraction of the stem bark of C. psidioides showed promising preliminary results. Separation of fractions and compounds of the root bark of T. kaiserana was performed using Lobar RP-18 column cromatography in order to investigate which fractions or compounds are responsible for the antimicrobial activity. The antimicrobial activity of the fractions was examined using the microdilution method. The most effective fraction against both S. aureus and P. aeruginosa was the fraction 2F8, which containsthe same compounds as the crude extract, but a higher concentration of polar ellagitannins which are probably responsible for the antimicrobial activity of this fraction. Also fraction 2F9 showed antimicrobial activity against P. aeruginosa. This fractions contains ellagic acid derivatives which are probably responsible for the antimicrobial activity. The crude extract of the root bark of T. kaiserana was also fractionated using RP-18 thin layer chromatography, because this method gave better separation compared to column chromatography. Due to limited time the antimicrobial activity of the TLC-fractions will be investigated in the future.