Studies on the antimicrobial, antioxidant and antiproliferative potential of the ethyl acetate extract and compounds of Peltophorum africanum
- Authors: Okeleye, Benjamin Ifeoluwa
- Date: 2014
- Language: English
- Type: Thesis , Masters , MSc (Microbiology)
- Identifier: vital:11282 , http://hdl.handle.net/10353/d1016165
- Description: Cells are constantly exposed to a variety of oxidizing agents, some of which are necessary for life. Oxidants produced in excess can cause an imbalance, leading to oxidative stress, especially in chronic bacterial, viral, and parasitic infections. This can result to damage of biomolecules such as lipids, proteins, and DNA, hence, an increased risk for cancer. Plants have a long history of use in the treatment of cancer. Plant secondary metabolites have proved to be an excellent reservoir of new medical compounds. Fruits, vegetables, and whole grains contain a wide variety of antioxidant phytochemicals, such as phenolics and carotenoids, and may help protect cellular systems from oxidative damage and also may lower the risk of chronic diseases. Peltophorum africanum, a member of the family Fabaceae (Sond) is also known as the African weeping wattle and is used in traditional medicine in South Africa. This study investigated the antimicrobial, antioxidant and antiproliferative potential of the ethyl acetate extract and compounds of Peltophorum africanum in order to validate its pharmacological use. The study assessed the in vitro antimicrobial activity of ethyl acetate extract (EAE) of Peltophorum africanum stem bark and its fractions by the agar well and macrodilution methods. The toxicity on a normal human liver cell (Chang liver cell) and antiproliferation of human breast (MCF-7), colon (HT-29) and cervical (HeLa) cancer cell lines were determined using the CellTiter-Blue cell viability assay and the mechanism of action delineated using the Nucleic Acid and Protein Purification Nucleospin® Tissue Kit, Scanning Electron Microscopy (SEM), Propidium iodide (PI) and Acridine orange (AO) double-staining techniques, the Cleaved Caspase 3 (Asp 175) Alexa Fluor® 488 Antibody and the Coulter® DNA PrepTM Reagents Kit. Purification and identification of the compounds from EAE and fractions as well as the morphological alteration of bacteria, yeast and cancer cells were determined using thin layer chromatography, infrared spectra fingerprint and GC-MS analysis, micro-dilution and scanning electron microscopy with energy-dispersive X-ray analysis. In vitro antioxidant activity of EAE was determined by means of radical scavenging and ferric reducing power analysis using 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2`-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) kit, hydrogen peroxide (H2O2), iron (iii) chloride (Fe3+) and nitric oxide (NO). To assess the likely effects of secondary metabolites on the activities observed; total proanthocyanidins, phenolics, flavonols, and flavonoids were determined using standard phytochemical methods. Data were analyzed by one way analysis of variance (ANOVA; SPSS Version 17.0, 2011), regression analysis (MINITAB, version 12 for windows), probit analysis test (software NCSS, 2007) and GraphPad Prism4 software package. The p-values < 0.05 were considered significant. Marked activity of the extract was observed against Plesiomonas shigelloides ATCC 51903, with MIC and MLC values of 0.15625 and 0.3125mg/mL, respectively. The extract was both bactericidal (MICindex ≤ 2) and bacteriostatic/fungistatic (MICindex > 2) in activity. Lethal dose at 50 (LD50) showed 82.64 ± 1.40 degree of toxicity at 24 hrs, and 95 percentile of cell death dose activity ranged from log 3.12 ± 0.01 to 4.59 ± 0.03. The activity of the eight fractions tested ranged from 1.0 ± 0.5 to 3.7 ± 1.6 mg/mL (IC50) and from 2.1 ± 0.8 to 6.25 ± 0 mg/mL (IC90) (Chapter 3). Due to the effect of compounds present in the crude extract and fractions, the P. aeruginosa treated with EAE had a reduction of sodium from 5.55 % (untreated) - 1.50 %. For C. albicans, pottasium was reduced from 4.16 % (untreated) - 0.76 % (T1). Remarkable morphological alterations were observed including deformation of the germ tubes and perforation of the cell wall (Chapter 4). Extract scavenging activity of 88.73± 6.69 % (25 μg mL-1), 53.93±1.09 % (25 μg mL-1) were recorded for H2O2 and NO respectively with proanthocyanidins (92.18±4.68 mg/g) occurring more (p < 0.05) in the extract compared to all other phenolics compounds (Chapter 5). Significant reduction in cell viability of the cells was noted as the MCF-7 cells were reduced from 100 - 54.33±1.84 % after 72 hrs of treatment with 5 μg/mL of EAE (P. value < 0.05). TEt10 was cytotoxic against human normal cells (chang liver cell) at EC50 of 37 μg/mL and 74 μg/mL after 24 and 48 h of treatment respectively. Marked antiproliferative activity of 13.2 μg/mL (EC50) was observed when HeLa cells were treated for 48 h. Internucleosomal DNA of MCF-7, HT-29 and HeLa cells randomly fragmented into an uninterrupted spectrum of sizes, complemented by the intercalation of nucleic acid-specific fluorochromes by PI and AO spotting two phases of apoptosis; early (EA) and late (LA) apoptosis. Distinctive ultramorphological changes observed include; cell shrinkage, membrane blebbing, and typical cell induced death. The study also recorded 705.102 ± 28.56 % TEt10 caspase-3 activity compared to curcumin 592.857 ± 165.76 % (positive control) and untreated (negative control; 100 ± 15.81 %) cells. Percentage HeLa cell with Sub-G1 DNA phase increased from 0.13 ± 0.06 % (negative control) to 13.8 ± 3.04 % compared to curcumin (8.17 ± 2.20 %) after treatment with TEt10. The compounds identified in the fractions including Colchicine, N-(trifluoroacetyl)methyl-N-deacetyl-, Lupeol and .gamma.-Sitosterol may be responsible for the induction of apoptosis observed and could be further studied in vivo as a potential template for new anticancer treatment (Chapter 6 & 7).
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- Date Issued: 2014
In vitro activity of bioactive compounds of selected South African medicinal plants on clinical isolates of Helicobacter pylori
- Authors: Okeleye, Benjamin Ifeoluwa
- Date: 2011
- Subjects: Helicobacter pylori , Microbial sensitivity tests , Traditional medicine -- South Africa , Gram-negative bacterial infections
- Language: English
- Type: Thesis , Masters , MSc (Microbiology)
- Identifier: vital:11255 , http://hdl.handle.net/10353/310 , Helicobacter pylori , Microbial sensitivity tests , Traditional medicine -- South Africa , Gram-negative bacterial infections
- Description: The stem bark of Peltophorum africanum and Bridelia micrantha are used in South Africa traditional medicine for treatment of intestinal parasites, relieve problems and human immunodeficiency virus/ acquired immune deficiency syndrome (HIV/AIDS). The growing problem of antibiotic resistance by Helicobacter pylori the major etiological agent in gastritis, gastric cancer, peptic and gastric ulcer demands the search for novel compounds from plant based sources. This study was aimed to determine the antimicrobial activity of five solvent (ethylacetate, acetone, ethanol, methanol and water) extracts of the stem bark of P. africanum and B. micrantha on clinical strains of H. pylori in a bid to identify potential sources of cheap starting materials for the synthesis of new drugs. H. pylori strains were isolated from patients presenting with gastric related morbidities at the Livingstone Hospital, Port Elizabeth for endoscopy and confirmed following standard microbiology procedures. The plant extracts including clarithromycin were tested against 31 clinical strains of H. pylori by the agar well diffusion method. The most potent extract was evaluated by the microdilution method to determine the Minimum Inhibitory Concentration (MIC50&90), followed by the rate of kill. Preliminary phytochemical analysis was carried out. The one way ANOVA test was used to statistically analyse the results. All the extracts demonstrated anti-H. pylori activity with zone diameters of inhibition that ranged from 0 to 23 mm for the extracts and 0 to 35 mm for clarithromycin. Marked susceptibility (100%) was recorded for the ethyl acetate extract of P. africanum (P. afr. EA) and the acetone extract of B. micrantha (B. mic. A), which were statistically significant (P < 0.05) compared to all other extracts and clarithromycin. For B. micrantha ethyl acetate extract, 93.5 percent susceptibility was observed while for the control iv antibiotic, clarithromycin it was 58.1 percent. The MIC50 ranged from 0.0048 to 0.313 mg/mL for P. afr. EA, and from 0.0048 to 0.156 mg/mL for B. mic. EA; MIC90 ranged from 0.156 mg/mL to 0.625 mg/mL and 0.0048 to 2.5 mg/mL for P. afr. EA and B. mic. EA respectively. There was a significant statistical difference observed in potency of both P. afr. EA and B. mic. A compared to the two antibiotics (P < 0.05). One hundred percent killing by P. afr EA was observed at 0.05 mg/mL (½ x MIC) and 0.2 mg/mL (2 x MIC) in 66 h for strain PE466C and PE252C respectively. For B. mic. EA, 100 percent killing effect of both strains (PE430C and PE369C) was observed at 0.1 mg/mL (2 x MIC) in 66 h. Qualitative phytochemical analysis confirmed the presence of alkaloids, flavonoids, steroids, tannins and saponins in the ethyl acetate extracts of both plants, which could be a potential template of lead molecule for the design of new anti- Helicobacter pylori therapies.
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- Date Issued: 2011