South Africa is a country of great diversity. Different climate zones and a host of
different habitats make South Africa the perfect platform for rich floral diversity. This
floral diversity lends itself to the study of natural products by discovering new natural
drugs that can be used in the treatment of many illnesses.
Studies into the antioxidant properties of plants that are used in traditional medicine
are an important aspect of research to determine the rationale of the use of plants by
traditional healers.
Many neurodegenerative diseases, like epilepsy, Parkinson s and Alzheimer s
diseases, are linked to oxidative stress. Antioxidants could play a major role as
neuroprotective agents and could alter the progression of these diseases.
Epilepsy is one of the world s most prevalent central nervous system disorders and
affects more than seventy per one thousand children in South Africa. Most of these
cases are people in rural areas of South Africa where communities rely on the use of
traditional medicine.
Cotyledon orbiculata L. var orbiculata (Haw.) DC. is widely used in traditional
medicine to treat epilepsy and other central nervous system disorders. The need to
screen these plants for activity and toxicity is very important to understand the
complex mechanism of action in the treatment of patients.
In this study the methanol extract and three different fractions of the methanol extract
of Cotyledon orbiculata were used to test for antioxidant activity and toxicity towards
neuroblastoma cells.
The freeze dried leaves of Cotyledon orbiculata were extracted with methanol using
a Soxhlet apparatus. The concentrated extracts were analysed using HPLC (high
pressure liquid chromatography) and three major peaks were selected for isolation.
Three assays were performed to assess the antioxidant activity and toxicity of the
isolated compounds.
The thiobarbituric acid assay (TBA) quantifies the extent of the inhibition of lipid
peroxidation in rat brain homogenates by the isolated fractions.
All of the samples were able to attenuate lipid peroxidation as seen from the results
obtained from the TBA assay. The methanol extract showed the best attenuation of
lipid peroxidation in the rat brain homogenate with fraction 1 and 2 showing greater
attenuation of lipid peroxidation than fraction 3.
The nitroblue tetrazolium assay (NBT) quantifies the ability of the fractions to
scavenge superoxide radicals in a rat brain homogenate.
All samples were able to scavenge superoxide radicals as indicated by the NBT
assay. The methanol extract showed the best superoxide scavenging abilities in the
assay whereas fraction 1 showed better scavenging abilities than fraction 2 and 3.
The 3–(4,5–dimethylthiazol–2–yl)–2,5–diphenyltetrazolium bromide assay (MTT)
indicates the toxicity of the fractions towards neuroblastoma cells.
The methanol extract and fraction 2 in the highest concentration of 10 mg/ml were
the only samples that showed toxicity towards neuroblastoma cells.
The molecular structure of a compound from fraction 2 was determined by using
nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), and
mass spectroscopy (MS). This compound was identified as diethyl malate. Diethyl
malate is an artefact that is generated in HPLC procedures in the presence of malic
acid (which naturally occurs in the leaves of Cotyledon orbiculata) and ethanol.
The methanol extract of Cotyledon orbiculata has high antioxidant activity and could
be due to the presence of malic acid in the leaves of the plant. The rationale in the
use of Cotyledon orbiculata in the treatment of epilepsy could not be determined due
to the isolation of an artefact, diethyl malate, obtained from the fraction.
Further research should include methods to prevent artefact formation and
purification of the samples that are obtained. / Thesis (MSc (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2012.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/8063 |
| Date | January 1900 |
| Creators | Roux, Wessel Cornelius |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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