Antidiabetic activity and mechanism of action of extracts of Brachylaena elliptica (Thurb.) DC. and Brachylaena ilicifolia (Lam) Phill & Schweick
- Authors: Sagbo, Idowu Jonas
- Date: 2017
- Subjects: Herbs -- Therapeutic use Pharmacognosy Diabetes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8154 , vital:31624
- Description: International Diabetes Federation (IDF) estimated that there are 415 million people globally that are suffering from diabetes and this figure is likely to double by 2040. In South Africa, the number of people suffering from diabetes is believed to be rising steadily and the current antidiabetic therapies include the use of expensive pharmaceutical drugs which after display numerous adverse side effects. Herbal medicine is an alternative treatment strategy used by many rural populations for the management of diabetes, which is cost-effective and with minimal reported side effects. The aim of this study was to validate the antidiabetic activity and to elucidate the possible mechanisms of action of the aqueous leaf extracts prepared from two plants, Brachylaena elliptica and Brachylaena ilicifolia, used by traditional healers in the Eastern Cape, South Africa for the treatment of diabetes. The current pharmaceutical drugs target site, including carbohydrate digestion, regulation of blood glucose levels through insulin levels or activating glucose uptake in liver and muscle. The plants extracts were therefore evaluated for their potential to mimic or replace these drugs. The inhibibitory effects on alpha amylase, alpha glucosidase, DPP-IV activity and pancreatic lipase were evaluated at various concentrations of the plant extracts. To evaluate the suitability of these extracts for cell based in vitro assay as well as to determine the safety of the plant extracts for human consumption, cytotoxicity towards HepG2 cells was assessed using the MTT assay. The effect of both plant extracts on glucose uptake in HepG2 and L6 cells, lipid accumulation in 3T3-L1 preadipocytes and NO production in RAW macrophages were investigated. Both plant extracts were also tested for INS-1 proliferation using the imageXpress®Micro XLS analysis. The MTT reduction assay was also used to investigate the effect of extracts on INS-1 glucose metabolism and as a reflection of insulin secretion. The inhibitory activity of the crude extracts of both plants on protein glycation, collagenase activity and CYP3A4 interaction were also evaluated The crude extracts of both plants displayed no significant inhibition on alpha amylase, alpha glucosidase, dipeptidyl peptidase-IV, lipase, protein glycation and collagenase compared to relevant standard inhibitors, acarbose, EGCG, Diprotin A, Orlistart and aminoguanidine. The mild inhibition of B. elliptica on alpha glucosidase activity at the highest concentration of the extract tested, was considered as not physiologically relevant. The aqueous extracts of bothplants showed < 40 percent cell death in HepG2 cells even at high concentration and hence support the use of the plants by traditional healers. The extracts of B. ellipticaat 25 µg/ml, displayed a proliferative effect on INS-1 cells when compared to the negative control and B. ilicifolia at 25 μg/ml. The treatment of HepG2 cells with 100 µg/mlB. elliptica and B. ilicifolia extracts revealed a higher glucose uptake of 121 percent and 123 percent respectively when compared to the pharmaceutical drug berberine. However, both plants extracts displayed weak significant glucose uptake in L6 muscle cell line at all the tested concentrations when compared to insulin at 6 μg/ml. The crude extracts of both plants demonstrated no significant effect on 3T3-L1 lipid accumulation and INS-1 glucose metabolism. The extracts of both plants strongly reduced NO production in RAW macrophages at the highest concentration (100 μg/ml) tested in this study, which at least in part, may be explained by the flavanoids and phenols content of these plants. In addition, the crude extracts of both plants displayed weak significant inhibition on the CYP3A4 activity indicating that both plant extracts do not interfere with the cytochrome P450 activation or metabolism of anti-diabetic drugs, that may be taken together with the plant extracts. In conclusion, the results obtained from this study revealed that both plants could possibly exert their hypoglycemic effect via interactions with insulin receptor, thereby enhancing glucose metabolism as well as maintaining and repairing the health state and function of the pancreatic beta cells. The findings in this study, therefore provide evidence that B. elliptica and B. ilicifolia possess antidiabetic properties, and support their folkloric use for the management of diabetes. However, due to the potential toxicity of both plant extracts, they must be prescribed with caution.
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- Date Issued: 2017
Fixed points of single-valued and multi-valued mappings with applications
- Authors: Stofile, Simfumene
- Date: 2013
- Subjects: Fixed point theory Mappings (Mathematics) Coincidence theory (Mathematics) Metric spaces Uniform spaces Set-valued maps
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5397 , http://hdl.handle.net/10962/d1002960
- Description: The relationship between the convergence of a sequence of self mappings of a metric space and their fixed points, known as the stability (or continuity) of fixed points has been of continuing interest and widely studied in fixed point theory. In this thesis we study the stability of common fixed points in a Hausdorff uniform space whose uniformity is generated by a family of pseudometrics, by using some general notations of convergence. These results are then extended to 2-metric spaces due to S. Gähler. In addition, a well-known theorem of T. Suzuki that generalized the Banach Contraction Principle is also extended to 2-metric spaces and applied to obtain a coincidence theorem for a pair of mappings on an arbitrary set with values in a 2-metric space. Further, we prove the existence of coincidence and fixed points of Ćirić type weakly generalized contractions in metric spaces. Subsequently, the above result is utilized to discuss applications to the convergence of modified Mann and Ishikawa iterations in a convex metric space. Finally, we obtain coincidence, fixed and stationary point results for multi-valued and hybrid pairs of mappings on a metric space.
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- Date Issued: 2013
Tangentially symplectic foliations
- Authors: Remsing, Claudiu Cristian
- Date: 1994
- Subjects: Geometry Problems, exercises, etc Geometry, Differential Symplectic manifolds Poisson manifolds Foliations (Mathematics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5419 , http://hdl.handle.net/10962/d1005233
- Description: This thesis is concerned principally with tangential geometry and the applications of these concepts to tangentially symplectic foliations. The subject of tangential geometry is still at an elementary stage. The author here systematises current concepts and results and extends them, leading to the definition of vertical connections and vertical G-structures. Tangentially symplectic foliations are then characterised in terms of vertical symplectic forms. Some significant particular cases are discussed.
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- Date Issued: 1994