Type 2 diabetes mellitus (T2DM) is an increasing global health concern, currently affecting an estimated 382 million individuals. There is no cure for T2DM and the search for new and improved treatments is ongoing. Presently, various pharmacological regimens are available to treat T2DM, but with varied success. Thousands of traditional herbs are also used to treat T2DM, but mainly without scientific validation. The aim of this study was to assess the polyphenolic content, antioxidant capacity, as well as in vitro toxicity and hypoglycaemic activity of a commercial ‘antidiabetic’ tea mixture (Diabetea) and its individual constituents: Achillea millefolium L. (Yarrow), Agathosma betulina Bartl. & Wendl. (Buchu), Salvia officinalis L. (Sage), Taraxacum officinalis L. (Dandelion), Thymus vulgaris L. (Thyme), Trigonella foenum-graecum L. (Fenugreek) and Urtica urens L. (Nettle). All herbs were tested as crude extracts, prepared using hot water (HW) and dichloromethane (DCM). The total polyphenolic content of each extract was determined using the Folin-Ciocalteau and aluminium trichloride methods. The non-cellular antioxidant activity was assessed using 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) methods. The cell-based antioxidant activity was measured against p-chloranil-induced generation of reactive oxygen species (ROS) in Ea.hy926 cells, using the fluorescent dye, 2',7'-dichlorfluorescein-diacetate (DCFH-DA). The effect of each extract on the viability of C2C12 myotubes, Ea.hy926 endothelial cells and human lymphocytes (HL) was determined using sulforhodamine B (SRB). The in vitro hypoglycaemic activity was assessed against α-amylase and α-glucosidase activity using 3,5-dinitrosalicylic acid (DNSA) and p-nitrophenyl-α-D-glucopyranoside (p-NPG), respectively. The type of inhibition exerted on these enzymes was determined using the Michaelis-Menten enzyme kinetics model, expressed as mixed, competitive, non-competitive and uncompetitive. Glucose uptake activity was measured using the 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-D-glucose (2-NBDG) fluorescent analogue. T. vulgaris and S. officinalis had the highest amount of polyphenols of all extracts tested. The HW extracts of T. vulgaris and S. officinalis showed significant (p < 0.05) cell-free antioxidant activity and cell-based radical scavenging activity. In addition, U. urens (HW) also limited cell-based ROS generation (p < 0.05). The Diabetea extracts presented with poor antioxidant activities, of which some had a pro-oxidant effect on Ea.hy926 cells. The positive linear relationship between antioxidant activity and polyphenolic content was shown to be dependent on the solvent type used. All of the DCM extracts had low antioxidant activity and polyphenolic content. None of the extracts produced < 50% cell density at the concentrations tested (1.3 - 20 μg/mℓ). In general, the DCM extracts showed a greater decrease in cell density than the HW extracts. The Ea.hy926 cells were the least affected by the extracts in terms of decreased cell density. The DCM extract of U. urens inhibited α-amylase activity in a mixed manner, which was comparable to the percentage inhibition exerted by the commercial drug, acarbose. Both the HW and DCM extracts of U. urens caused a significant (p < 0.05) increase in glucose uptake into C2C12 myotubes. The HW extract of T. vulgaris had a significant (p < 0.05) inhibitory activity against α-glucosidase (mixed). It also caused the uptake of glucose into C2C12 myotubes, which was significantly (p <0.05) more active than insulin. S. officinalis (DCM extract) also inhibited α-glucosidase activity (p < 0.05) in a mixed manner. Its HW extract displayed potent hypoglycaemic potential by causing glucose uptake into C2C12 myotubes, which was more significant (p < 0.05) than the activity of the positive control, insulin. The DCM extract of A. betulina was active against α-glucosidase (non-competitive), which was comparable to the activity of acarbose. Its HW extract also showed a significant (p < 0.05) glucose uptake activity. Furthermore, the DCM extracts of T. officinalis, A. millefolium, Diabetea and HW extracts of T. foenum-graecum and T. officinalis also caused a significant (p < 0.05) increase in glucose uptake into C2C12 myotubes. This study provides evidence for the antidiabetic potential of T. vulgaris and S. officianlis, in terms of antioxidant capacity and potential to prevent of post-prandial hyperglycaemia and alleviate hyperglycaemia by mimicking the action of insulin. In addition, the organic preparation of U. urens is also a potent α-amylase inhibitor. All herbs tested in this study exerted some form of in vitro antidiabetic activity. The Diabetea mixture, as a traditional preparation, did not have a significant antidiabetic capacity. In vitro observations from this study do not support the use of Diabetea as an antidiabetic preparation and reveal that some of the individual extracts prove more efficacious than the herb mixture. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Pharmacology / MSc / Unrestricted

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2016-09-26T14:16:09Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_Simone_Pacheco_Frutos da família Myrtaceae_Caracterização físico-química e potencial .pdf: 1364587 bytes, checksum: 6df19769efc9216d28d9614070c8e6af (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2016-09-26T18:34:47Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_Simone_Pacheco_Frutos da família Myrtaceae_Caracterização físico-química e potencial .pdf: 1364587 bytes, checksum: 6df19769efc9216d28d9614070c8e6af (MD5) / Made available in DSpace on 2016-09-26T18:34:47Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação_Simone_Pacheco_Frutos da família Myrtaceae_Caracterização físico-química e potencial .pdf: 1364587 bytes, checksum: 6df19769efc9216d28d9614070c8e6af (MD5) Previous issue date: 2015-03-27 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / As espécies vegetais Campomanesia xanthocarpa (guabiroba), Eugenia uniflora (pitanga), Eugenia pyriformis (uvaia), Psidium cattleianum (araçá) e Syzygium cumini (jambolão) estão presentes na Floresta Atlântica e são utilizadas pela população, para tratar diversas patologias, especialmente o diabetes melito tipo 2. Entretanto, a eficácia destes tratamentos e o mecanismo envolvido ainda não foram totalmente elucidados. Neste contexto, o presente estudo teve como objetivo principal avaliar o potencial dos compostos naturais destes frutos em inibir as enzimas α-amilase e α- glicosidase que estão envolvidas no metabolismo de carboidratos. Estes frutos também foram avaliados físico-quimicamente, realizando-se dentre outras análises a quantificação dos compostos fenólicos totais e a determinação da atividade antioxidante (métodos ABTS e DPPH). Os extratos metanólicos de P. cattleianum (acesso 44), S. cumini e E. pyriformis (acessos 11 e 15) inibiram de forma significativa a atividade da α-amilase. Os extratos metanólicos de P. cattleianum (acessos 44 e 87) também inibiram a atividade da α-glicosidase, utilizando-se os substratos maltose e sacarose. Em virtude da atividade antioxidante, da elevada quantidade de compostos fenólicos e da capacidade de inibição das enzimas digestivas do metabolismo de carboidratos, os frutos de P. cattleianum (acessos 44 e 87), S. cumini e E. pyriformis (acessos 11 e 15) podem apresentar potencial uso no manejo da hiperglicemia pós-prandial. / Campomanesia xanthocarpa (guabiroba), Eugenia uniflora (pitanga), Eugenia pyriformis (uvaia), Psidium cattleianum (araçá) and Syzygium cumini (jambolão) grow in the Brazilian Atlantic Forest and their fruits are commonly used as medicine to treat diseases related to carbohydrate metabolism, such as diabetes. The effectiveness of these treatments has not been demonstrated neither the biochemical mechanism involved. Therefore this study was devised to evaluate the potential of natural compounds of these fruits to inhibit key enzymes α-amylase and α- glucosidase involved in the carbohydrate metabolism. The fruits were also subjected to physicochemical characterization, quantification of phenolics compounds and antioxidant activity (ABTS and DPPH methods). The methanolic extracts of P. cattleianum (access 44), S. cumini, E. pyriformis (accesses 11 and 15) distinctively inhibited α-amylase activity. The methanolic extracts of P. cattleianum. (accesses 44 and 87) also inhibited α-glycosidase activity, with either maltose or sucrose as substrate. By having antioxidant activities, a fairly content of phenolic compounds, and capacity to inhibit carbohydrate digestive enzymes, P. cattleianum (access 44 and 87), S. cumini and E. pyriformis (accesses 11 and 15) could be good candidates to be used in the management of postprandial hyperglycemia.

Masters of Science / The aim of this study was therefore to evaluate the antioxidant and anti-diabesity potential of a hot water extract of C. maculata in non-cell based assays and correlate the activities with phenolic composition. Total antioxidant capacity (TAC) was assessed in terms of free radical scavenging and iron reducing ability. The DPPH, ABTS, ORAC and FRAP assays were employed. Anti-diabesity potential was assessed in terms of the inhibition of the digestive enzymes, α-glucosidase and pancreatic lipase