Abstract
Triumfetta welwitschii has been used as a traditional medicine in Africa. It is documented as a rich source of phytochemicals with antibacterial activities. To further explore the antibacterial potential of these phytochemical components, the phytochemical profile of the dichloromethane: methanol leaf extract from T. welwitschii was investigated using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Compounds were isolated from the extract using column chromatography and thin-layer chromatography. Compound B1 was isolated from the fraction eluted by 90 hexane:10 ethyl acetate using column chromatography. The antibacterial activity of B1 against Pseudomonas aeruginosa was evaluated in vitro using the broth microdilution method and the iodonitrotetrazolium (INT) colorimetric assay. The antibiofilm activities of the extract and B1 against P. aeruginosa were determined by quantifying the biofilms using crystal violet. The effect of the extract and B1 on capsular polysaccharide and extracellular DNA content of biofilm formed by P. aeruginosa was determined using phenol-sulphuric acid and propidium iodide, respectively. A total of 28 peaks were detected and identified using UPLC-MS/MS. The three most abundant phytochemicals identified were catechin, umbelliferone, and a luteolin derivative. B1 showed antibacterial activity against P. aeruginosa with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) value of 25 μg/ml. Only 38% and 6% of the biofilms were formed in the presence of the extract and B1, respectively. The extract and B1 reduced the capsular polysaccharide content in biofilms formed in P. aeruginosa by 40% and 65%, respectively. The extract and B1 significantly reduced the extracellular DNA content of biofilms by 29% and 72%, respectively. The results of this study provide evidence of the antibacterial and antibiofilm activities of B1 and leaf extracts from T. welwitschii. Future work should identify the chemical structure of B1 using nuclear magnetic resonance and mass spectrometry.
Highlights
Antimicrobial agents play a vital role in reducing the global burden of infectious diseases
Leaves of T. welwitschii were collected from the centenary (16.8°S, 31.1167°E, and 1156 m above sea level). e plant’s identity was authenticated by a botanist and a voucher specimen was deposited under the reference number C16 E7. e leaves were dried under shade for 14 days and powdered to yield a sample with a mass of 2350 g. e powder was macerated with a mixture of DCM: methanol (1 : 1 v/v) for 48 hrs at room temperature. e extract was concentrated under an RII rotary evaporator (BUCHI, LabortechnikAG, Switzerland) and dried under a stream of air to create a residue (147 g) that constituted the crude extract
A Ultra-performance liquid chromatography (UPLC)-mass spectrometry (MS)/MS chromatogram of the DCM: methanol leaf extract from T. welwitschii showing a total of 28 peaks with varying relative abundances was depicted in Figure 1. ree dominant peaks of 161, 191, and 359 m/z were detected
Summary
Antimicrobial agents play a vital role in reducing the global burden of infectious diseases. E rapid global spread of resistant bacterial isolates necessitates the discovery of novel antimicrobial agents that control infections. E EPSs enhance a biofilm community’s ability to forage for both water and nutrients from the environment. This forage mechanism of EPS is not deterred in adverse environments, a phenomenon that enables biofilm-producing bacteria to persist in atypical conditions. Biochemistry Research International faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. ese pathogens can “evade” the effects of antimicrobial treatment due to the acquisition of resistance genes and the formation of biofilms facilitated by EPSs. Targeting of the EPSs could disrupt biofilm physiology because a reduction in EPSs diminishes the hydrated barrier between cells and their external environment
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