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Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress
Dissertation (MSc)--University of Pretoria, 2013.
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University of Pretoria
2013
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| _version_ | 1867613519782871040 |
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| access_status_str | Open Access |
| author2 | Gulumian, Mary |
| author_browse | Gulumian, Mary |
| author_facet | Gulumian, Mary |
| collection | Thesis |
| dc_rights_str_mv | © 2012, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria |
| description | Dissertation (MSc)--University of Pretoria, 2013. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/29733 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:37:26.754Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/29733 Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress Gulumian, Mary Steenkamp, Vanessa Cromarty, Allan Duncan wcordier@gmail.com Cordier, Werner Syzygium cordatum Reactive oxygen species Polyphenols Oxidative stress Lipid peroxidation Glutathione Aaph Antioxidant Apoptosis Burkea africana UCTD Dissertation (MSc)--University of Pretoria, 2013. Free radicals have been implicated in the progression of various diseases, such as cancers and cardiomyopathies. When the body is overburdened with free radicals and endogenous antioxidants become depleted, oxidative stress ensues with resultant damage to biomolecules. During oxidative stress high levels of reactive oxygen species are generated, cellular viability decreases, and apoptosis and lipid peroxidation are induced. Supplementation with exogenous supplements rich in antioxidants, such as herbal remedies containing polyphenols, could result in increased protection against oxidative stress. The aim of the study was to assess the effect of Burkea africana and Syzygium cordatum in a cellular oxidative stress model for the potential development of an antioxidant supplement. Crude aqueous and methanolic extracts were prepared by solvent maceration, while a polyphenolic-rich extract was created through liquid-liquid extraction. Polyphenolic content and antioxidant activity was assessed in cell-free systems. Polyphenolic content was determined through the Folin-Ciocalteau and aluminium trichloride methods, while antioxidant activity was assessed by the Trolox Equivalence Antioxidant Capacity and 1,1-diphenyl-2-picrylhydrazyl radical assays. Identification of phytochemical classes was done through thin layer chromatography and biochemical reactions. Inherent cytotoxicity of samples was determined in four cell cultures (3T3-L1 pre-adipocytes, C2C12 myoblasts, normal human dermal fibroblasts and U937 macrophage-like cells) using the neutral red uptake assay. The effect on oxidative stress was assessed in 2,2`-azobis-(2-methylpropionamidine) dihydrochloride-exposed U937 macrophage-like cells with regards to reactive oxygen species generation, cytotoxicity, apoptosis, lipid peroxidation and GSH depletion. Both B. africana and S. cordatum showed enrichment of polyphenols from the aqueous extract, to methanolic extract, to polyphenolic-rich extract. Antioxidant activity showed the same trend, which correlated well with the increased concentration of polyphenols, such as catechin, gallic acid and myricetin. Samples indicated toxicity in the 3T3-L1 and C2C12 cell lines, though no toxicity was noted in the U937 cell line and normal human dermal fibroblast cultures. Free radical-induced generation of reactive oxygen species, cytotoxicity, lipid peroxidation and apoptosis was successfully reduced by crude extracts of B. africana and the polyphenolic-rich extracts of both plants between concentrations of 10 and 20 ìg/ml. The crude extracts of S. cordatum were mostly ineffective in reducing these parameters, even though cell viability was increased. B. africana pre-treatment decreased reduced glutathione concentrations significantly in a dose-dependent manner, while the methanolic and polyphenolic-rich extract of S. cordatum increased concentrations moderately. Polyphenolic-rich extracts of B. africana and S. cordatum had the most potent decrease in oxidative stress-related parameters in the present study, which could be attributed to the polyphenolic content and antioxidant activity. Limited cytotoxicity was apparent in two of the four cell lines tested; further isolation and purification needs to be carried out to assess the bioactive constituents which do not elicit a toxic response. Further investigation through the use of quantitative structure–activity relationship modeling could give more insight on conformational and chemical changes that need to be brought about to modify the bioactive phytochemicals for reduced cytotoxicity, but increased antioxidant activity. Copyright Pharmacology unrestricted 2013-09-07T16:26:03Z 2013-01-07 2013-09-07T16:26:03Z 2012-09-07 2013-01-07 2012-11-23 Dissertation Cordier, W 2012, Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/29733 > E12/9/195/gm http://hdl.handle.net/2263/29733 http://upetd.up.ac.za/thesis/available/etd-11232012-163955/ © 2012, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria application/pdf University of Pretoria |
| spellingShingle | Syzygium cordatum Reactive oxygen species Polyphenols Oxidative stress Lipid peroxidation Glutathione Aaph Antioxidant Apoptosis Burkea africana UCTD Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress |
| title | Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress |
| title_full | Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress |
| title_fullStr | Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress |
| title_full_unstemmed | Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress |
| title_short | Effects of polyphenolic-rich bark extracts of Burkea africana and Syzygium cordatum on oxidative stress |
| title_sort | effects of polyphenolic rich bark extracts of burkea africana and syzygium cordatum on oxidative stress |
| topic | Syzygium cordatum Reactive oxygen species Polyphenols Oxidative stress Lipid peroxidation Glutathione Aaph Antioxidant Apoptosis Burkea africana UCTD |
| url | http://hdl.handle.net/2263/29733 http://upetd.up.ac.za/thesis/available/etd-11232012-163955/ |