Browsing by Author "Weitz, Frans"

Now showing 1 - 7 of 7
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    Effect of Cissampelos capensis rhizome extract on human spermatozoa in vitro
    (Wiley, 2014) Shalaweh, Salem; Henkel, Ralf; Erasmus, N.; Weitz, Frans
    Cissampelos capensis is commonly known by the Afrikaans name ‘dawidjies’ or ‘dawidjieswortel’. C. capensis is the most important and best-known medicinal plant of the family Menispermaceae used by the Khoisan and other rural people in the western regions of South Africa. Among numerous other ailments, it is traditionally taken to treat male fertility problems. Yet, no studies have investigated the effects of this plant or its extracts on human spermatozoa. The aim of study was to investigate the effects of C. capensis extracts on sperm function. A total of 77 semen samples were collected. Spermatozoa were washed with HTF-BSA medium and incubated with different concentrations of C. capensis (0, 0.05, 0.5, 5, 50, 200 μg ml−1) for 1 h at 37 °C. Sperm motility, vitality, acrosome reaction, reactive oxygen species (ROS), capacitation, Annexin V binding, DNA fragmentation and mitochondrial membrane potential (Δψm) were determined. While viability, Annexin V positivity and Δψm were not affected, the percentages of ROS-positive, TUNEL-positive, capacitated and hyperactivated spermatozoa increased significantly and dose-dependently. It is concluded that the alkaloids present in the extract of C. capansis rhizomes triggered sperm intrinsic superoxide production leading to sperm capacitation and DNA fragmentation.
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    An evaluation of the biopesticidal characteristics of Helichrysum marifolium and Helichrysum patulum and their effects on animal metabolism
    (University of the Western Cape, 2002) Speelman, Abigail; Weitz, Frans
    There ate a number of pesticides that are suspected to be endocrine disrupters' Many of these pesticides are man-made. Endocrine disrupters are chemicals that can lead to an increase in birth defects, sexual abnormalities, and reproductive failure. Marine animals seem to be the most vulnerable to the effects of pesticides since the ocean is the final sink for many pollutants. Endocrine disrupters can exert their effects in many ways. They can either bind to the hormone's receptor and mimic the hormone, or block the action of the hormone' An experiment done of newborn female rats injected with 1mg DDT/day on days 2-4 after birth had early onset of puberty and accelerated loss of fertility. ln another experiment, vinclozolin (also a pesticide) at dosage levels of 3mg/kg/day resulted in feminised male rats in the womb and an abnormal number of nipples were observed (11). Pesticides can be absorbed through the skin, by inhalation or oral ingestion. There are, however, important quantitative differences between the various derivatives. The skin poorly absorbs DDT in solution, whereas dieldrin absorption by the skin is very efficient. The major effects of insecticides in humans are qualitatively similar and cause effects on the central nervous system (9).
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    A global revision of the nongeniculate coralling algal genere Porolithon Foslie (defunct) and Hydrolithon Foslie (Corallinales, Rhodophyta)
    (University of the Western Cape, 2005) Maneveldt, Gavin W.; Keats, Derek; Weitz, Frans; Faculty of Science
    The purpose of this thesis was to provide a revision and characterization of the species of nongeniculate coralline algae previously ascribed to the now defunct genus Porolithon; to provide a modern account of selected taxa from the genus Hydrolithon and descriptions of taxa found to conform the generic delimitation of Hydrolithon and to use a phenetic cluster analysis to determine the taxonomic relationships between the various taxa ascribed to the genera Polorithon and Hydrolithon.
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    Phytochemical screening and biological activity studies of five South African indigenous medicinal plants
    (Academic Journals, 2010) Babajide, Jelili Olalekan; Mabusela, Wilfred T.; Green, Ivan; Ameer, Farouk; Weitz, Frans; Iwuoha, Emmanuel I.
    Different extracts and fractions of five selected indigenous South African medicinal plants, namely, Cissampelos capensis, Geranium incanum and three Gethyllis species, were subjected to phytochemical screening and testing for cytotoxicity using the brine shrimp lethality bioassay, and antimicrobial activity assays against nine microbes, which included three fungal species, three Gram negative and three Gram positive bacteria.The majority of the extracts tested positive for the presence of tannins, phenolics and flavonoids, while in selected cases, phytochemical tests suggested the presence of essential oils, glycosides or alkaloids. The methanol extract of Gethyllis gregoriana displayed the highest cytotoxicity levels. Generally, the highest levels of biological activity were shown to reside in the methanolic extracts, while hexane extracts revealed very low to zero activity. The total tertiary alkaloid (TTA) of C. capensis was mostly active against Bacillus subtilis, a Gram +ve bacteria. The trends observed for the cytotoxicity assay were in agreement with those observed for the antimicrobial assay.
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    The scientific merit of Carpobrotus mellei L. based on antimicrobial activity and chemical profiling
    (Academic Journals, 2006) Springfield, E. P.; Weitz, Frans
    Species of the genus Carpobrotus are similar in appearance and have been used for medicinal purposes over many generations. Carpobrotus mellei is endemic to the south-Western Cape of South Africa, and also used for various ailments. To date no scientific validation and information has been reported on C. mellei. This study investigated the antimicrobial potential of C. mellei against Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and Mycobacterium smegmatis, and determined the minimum inhibitory concentrations (MIC) by two-fold serial dilution. C. mellei showed antimicrobial activity against S. aureus and M. smegmatis in the disc diffusion method. Eight chemical compounds showed clear zones of inhibition in the bioautograms, seven against S. aureus and three compounds were active against M. smegmatis. The ethyl acetate extracts have MIC values of 7.5 mg/ml and 15 mg/ml against S. aureus and M. smegmatis, respectively. Phytochemical tests indicated the presence of flavonoids, hydrolysable tannins, phytosterols and aromatic acids. High performance liquid chromatography (HPLC) showed a species-specific spectrum at a wavelength of 280 nm. The results confirm that C. mellei has scientific merit, and can substitute one of the other Carpobrotus species for antimicrobial usage within the south-Western Cape of South Africa.
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    Specias delimitation and assessment of genetic variability in Carpobrotus (Alzoaceae): evidence from amplified fragment length polymorphisms
    (University of the Western Cape, 2004) Khunou, Angeline; Reeves, Gail; Weitz, Frans
    Species of Carpobrotus (Aizoaceae: Ruschioideae) are widely spread throughout South Africa and are commonly used for their medicinal properties. The genus consists of 13 species of which seven occur in South Africa, five in Australia and one in Chile. A number of investigations on South African species have demonstrated that some taxa exhibit anti-microbial activity. Using AFLPs (amplified fragment length polymorphisms) this study was undertaken with the primary aim of resolving relationships between Carpobrotus species in South Africa, and determining species limits by assessing their genetic distinctness. In addition, levels of genetic variability among populations of two South African species, C. acinaciformis and C. edulis werc assessed in more detail. AFLPs were not able to resolve conflict surrounding species boundaries, perhaps due to extensive hybridization. However, major groupings within South African species were identified, although no geographical structuring of these populations was evident. From a bio-prospecting perspective caution needs to be taken when sampling Carpobrotus due to difficulty in identifying species possibly as a result of hybridization.
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    Species-level phylogenetic reconstruction of the African cycad genus Encephalartos (Zamiaceae)
    (University of the Western Cape, 2007) Mabunda, Makhegu Amelia; Weitz, Frans; Reeves, Gail; Donaldson, John; Faculty of Science
    This thesis explores species-level phylogenetic relationships of the African cycad genus Encephalartos, which is one of the eleven genera of cycads. The genus is confined to Africa and comprises approximately 65 species, 38 of which are found naturally in South Africa. The phylogenetic studies on Encephalartos to date still result in many unresolved polytomies so it is not possible to fully understand the relationships between different taxa. In this study, AFLPs were used together with DNA sequencing to reconstruct the phylogenetic relationships of the genus. This study is the first to be presented with aims of resolving the relationships of Encephalartos using AFLPs together with DNA sequences. Total DNA was extracted from accessions sampled from the Kirstenbosch Botanical Garden and the Montgomery Collection, representing the majority of Encephalartos species listed in the most recent world list of cycads. Sequences of the trnL intron, rpoC1, ITS 1, ITS 2, and AFLP profiles from two sets of selective primers were used to reconstruct the phylogenetic relationships within the genus using maximum parsimony methods. As in earlier studies, unresolved polytomies were recovered from the sequencing data. The AFLP trees have some resolution but CI and RI indices were low indicating high levels of homoplasy in the data. The relationships resolved by this study for all the data sets separately and combined were different to those previously suggested for the genus. The biogeography of Encephalartos is also investigated by habitat optimization of the genus to estimate the origin of the genus with respect to its current distribution.