Browsing by Subject "Combretum"

Antimicrobial resistance is a growing problem worldwide. It has been shown that more than 70% of the bacteria that cause nosocomial infections are resistant to at least one antibiotic commonly used to treat them. Two concomitant phenomena that aggravate the diarrheal disease situation, especially in developing countries, are general contamination (spread of pathogens due to unclean water, poor sanitation, and malnutrition) and resistant bacterial strains (the adverse consequences of infections increase as infections prolong). According to the WHO, foodborne diseases (FBDs) were estimated to have caused approximately 91 million people to become ill and 137,000 deaths in Africa in 2010. The number is about a third of the deaths caused by FBD worldwide. Diarrhea caused about 70% of the FBD burden. Bacteria that cause food poisoning include Bacillus cereus, Campylobacter jejuni, Clostridium botulinum, Clostridium perfringens, Cronobacter sakazakii, Esherichia coli, Listeria monocytogenes, Salmonella spp., Shigella spp., Staphylococccus aureus and Yersinia enterocolitica, some of which are discussed in more detail in this master’s thesis; antibiotics against which resistance has developed, how bacteria resist antibiotics, and the emergence of resistance in Africa. The antibiotic resistance of bacteria and the mechanisms of resistance against antimicrobial drugs are also discussed shortly. In addition to food poisoning, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus can cause difficult-to-treat infections such as wounds. In addition, this work has first dealt with antimicrobial plant derived compounds in general and their modes of action, and then focused on compounds, fractions and extracts of species of the genera Combretum, Terminalia, Pteleopsis and Anogeissus, as well as their antibacterial effects and uses in traditional medicine. In addition, the antibacterial mechanisms of action of different groups of compounds have been discussed in more detail. This work also deals with the combination studies of some plant extracts, fractions and compounds with antibiotics. Combination studies with antibiotics have generally been studied less than the antibacterial effects alone or the effects of combinations of many plant extracts, as used in African traditional medicine. The experimental part covers, among other things, the preparation and yield determination of crude extracts (water and methanol) as well as the agar diffusion method, the microdilution method, the Time kill tests and the checkerboard method in interaction tests to determine MIC, MBC and FIC values. Due to the Covid 19 pandemic, study results were obtained only by the agar diffusion method against Bacillus cereus. The most antimicrobial extracts were extracts of species of the genus Terminalia.

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.