Thesis (Ph.D. (Botany)) -- University of Limpopo, 2023 / The use of medicinal plants as a source of treatment for various ailments including
fungal infections is still practised in South Africa and across the globe. Fungal
infections especially of Cryptococcus, Candida and Aspergillus species are the main
cause of morbidity and mortality worldwide, particularly in developing countries.
Traditional medicine is used as a source of remedies worldwide and has contributed
extensively towards the development of modern medicine. Twelve selected medicinal
plants (Kleinia longiflora DC. Berchemia discolor (Klotzsch) Hemsl., Persea americana
Mill., Sansevieria hyacinthoides (L.) Druce, Dichrostachys cinerea (L.) Wright &Arn,
Withania somnifera Dunal (Ashgandh), Momordica balsamina L., Lonchocarpus
capassa, Pappea capensis, Rhus lancea L. fil, Peltophorum africanum, Maytenus
heterophylla (Eckl. & Zeyh.) Robson) were analysed qualitatively for antifungal
activities against Aspergillus fumigatus, Candida albicans and Cryptococcus
neoformans.
The plant materials were extracted with solvents of various polarities such as acetone,
dichloromethane, methanol, hexane, and water. Methanol extracted the highest
amount of crude extracts from all the plant species as compared to other organic
solvents. Chemical components of the extracts were analysed using aluminum backed Thin Layer Chromatography (TLC) plates and developed using three different
eluent systems: Ethyl acetate: methanol: water [EMW], Chloroform: ethyl acetate:
formic acid [CEF] and Benzene: ethanol: ammonia hydroxide [BEA]. CEF was the best
eluent solvent system since it separated more compounds from plant extracts. This
indicates that the active compounds were relatively non-polar. More chemical
compounds were observed in TLC chromatograms separated with CEF, followed by
BEA and EMW. All plant extracts had shown different chemical components when
separated from the three solvent systems.
The bioautography and serial dilution assays were used to determine the biological
activity of plant extracts against the tested microorganisms, respectively. All the tested
plant extracts revealed some varying degrees of fungal inhibition, with minimum
inhibitory concentrations (MIC) values ranging between 0.02 mg/ml and 2.5 mg/ml.
The aqueous extracts had shown some activity against the tested microorganisms.
Noteworthy, antifungal activity was observed in acetone, DCM, hexane, and methanol
root extracts of D. cinerea against the three tested microorganisms with MIC values
ranging between 0.02 mg/ml and 0.04 mg/ml. Furthermore, acetone extracts of D.
cinerea and P. africanum had excellent activity against three fungal pathogens with
MIC values of 0.02 mg/ml and 0.08 mg/ml. Active compounds were observed in
dichloromethane extracts of W. somnifera with Rf values of 0.40 and 0.64. In TLC
chromatograms separated with BEA, active compounds were observed in acetone,
hexane, and methanol leaf extract of P. americana, this indicates that the fungal
compounds were relatively non-polar. No active compounds were observed in plant
extracts of K. longiflora. Active compounds were visible in all extracts of P. capensis
in TLC chromatograms developed in CEF and EMW.
The antioxidant present in plants prevents the free radicals from causing various
diseases in humans by inhibiting the oxidation of free radicals at the cellular level. The
qualitative and quantitative 1,1-diphenyl-2-picrylhydrazyl (DPPH) methods were used
to determine the antioxidant activities of plant extracts. The presence of antioxidant
compounds was indicated by yellow bands against the purple background on the TLC
plates. More antioxidant compounds were observed in acetone and dichloromethane
extracts of S. hyacinthoides developed in BEA compared to other plant species tested.
Methanol, hexane, and water extracts of L. capassa revealed good antioxidant activity
against DPPH by having a high percentage of inhibition compared to other solvents.
Noticeably, extracts of P. africanum possess strong antioxidant activity as compared
to other plant species.
Solvent-solvent fractionation using column chromatography of the acetone extract led
to the isolation of six compounds. The biological activity of the isolated compounds of
L. capassa was investigated against the tested pathogenic fungi. The isolated
compounds revealed some varying degrees of inhibition to the fungal pathogens. The
largest quantity was isolated from compound 1 (80 mg), compound 4 (39 mg),
compound 3 (27 mg), compounds 2 and 5 (14 mg) and the least was compound 6 (4.8
mg). However only three compounds were successfully identified as Lupeol
(compound 1), Friedelin (compound 3) and 6-(γ,γ-Dimethylallyl)-3’,4’-dimethoxy-6”,6”-
dimethylpyrano-[2”,3”:7,8]-flavanone (compound 4). Compounds 2, 5 and were not
identified due to some impurities.
More importantly, the isolated compounds exhibited good antioxidant activity in
qualitative and quantitative scavenging assays, which indicates that isolated
compounds of L. capassa can scavenge the free radicals causing fungal infections in
humans. The results support the traditional use of the selected plants to combat fungal
infections and related ailments by the local people and traditional health practitioners
in Vhembe District, Limpopo Province.
The (3-(4,5-dimethylthiazol) -2,5-diphenyltetrazoliumbromide) (MTT) assay was used
to determine the toxic effects of the plant crude extract and isolated compounds.
Lupeol and 6-(γ,γ-Dimethylallyl)-3’,4’-dimethoxy-6”,6”-dimethylpyrano-[2”,3”:7,8]-
flavanone revealed the same degree of cytotoxicity against the Vero monkey kidney
cells. All the compounds were not toxic with an LC50 value of ˃ 0.2 mg/ml. / University of Limpopo and
National Research Foundation
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/4291 |
| Date | January 2023 |
| Creators | Machaba, Tambudzani Caroline |
| Contributors | Mahlo, S.M., Eloff, J. N. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xxii, 155 leaves |
| Relation |
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