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Search Results: 1 - 10 of 36906 matches for " Johannes Van Staden "
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In Vitro Antioxidant Properties, HIV-1 Reverse Transcriptase and Acetylcholinesterase Inhibitory Effects of Traditional Herbal Preparations Sold in South Africa
Ashwell R. Ndhlala,Jeffrey F. Finnie,Johannes Van Staden
Molecules , 2010, DOI: 10.3390/molecules15106888
Abstract: The antioxidant potentials for fourteen multipurpose traditional herbal preparations sold in South Africa were determined using the DPPH radical scavenging, ferric reducing power and β-carotene-linoleic acid model system, the anti-HIV-1 reverse transcriptase (RT) enzyme inhibitory effects using an ELISA kit and acetylcholinesterase (AChE) enzyme inhibition using the microtitre plate assay. Nine of the herbal mixtures (Umzimba omubi, Umuthi wekukhwehlela ne zilonda, Mvusa ukunzi, Umpatisa inkosi, Imbiza ephuzwato, Vusa umzimba, Supreme one hundred, Sejeso herbal mixture Ingwe? and Ingwe? special muti) exhibited higher antioxidant potentials, while only four (Imbiza ephuzwato, Ingwe? muthi mixture, Sejeso herbal mixture Ingwe? and African potato extractTM) showed potent activity against the RT enzyme. Nine mixtures (Imbiza ephuzwato, Umpatisa inkosi, African potato extractTM, Sejeso herbal mixture Ingwe?, Vusa umzimba; Ingwe? muthi mixture, Ibhubezi?, Lion izifozonke Ingwe? and Ingwe? special muti) showed AChE enzyme inhibitory activity greater than 50%. The observed activity exhibited by some of the herbal mixtures gives some credence to the manufacturers’ claims and goes part of the way towards validating their use against certain conditions such as oxidative stress, HIV/AIDS proliferation and some mental conditions. It is however, desirable to carry out further studies to determine the effects of mixing plant species/parts in one mixture on the antioxidant potency as well as isolating active constituents from the herbal mixtures.
Natural Antioxidants: Fascinating or Mythical Biomolecules?
Ashwell R. Ndhlala,Mack Moyo,Johannes Van Staden
Molecules , 2010, DOI: 10.3390/molecules15106905
Abstract: Research on the use, properties, characteristics and sources of antioxidants especially phenolic compounds, flavonoids, vitamins, synthetic chemicals and some micronutrients began in the late 18th century. Since then antioxidant research has received considerable attention and over a hundred thousand papers have been published on the subject. This has led to a rampant use of antioxidants in order to try to obtain and preserve optimal health. A number of nutraceuticals and food supplements are frequently fortified with synthetic or natural antioxidants. However, some research outcomes have led to the belief that antioxidants exist as mythical biomolecules. This review provides a critical evaluation of some common in vitro antioxidant capacity methods, and a discussion on the role and controversies surrounding non-enzymatic biomolecules, in particular phenolic compounds and non-phenolic compounds, in oxidative processes in an attempt of stemming the tidal wave that is threatening to swamp the concept of natural antioxidants.
Antioxidant and acetylcholinesterase-inhibitory properties of long-term stored medicinal plants
Stephen O Amoo, Adeyemi O Aremu, Mack Moyo, Johannes van Staden
BMC Complementary and Alternative Medicine , 2012, DOI: 10.1186/1472-6882-12-87
Abstract: The phytochemical, antioxidant and acetylcholinesterase-inhibitory properties of 21 medicinal plants were evaluated after long-term storage of 12 or 16 years using standard in vitro methods in comparison to freshly harvested materials.The total phenolic content of Artemisia afra, Clausena anisata, Cussonia spicata, Leonotis intermedia and Spirostachys africana were significantly higher in stored compared to fresh materials. The flavonoid content were also significantly higher in stored A. afra, C. anisata, C. spicata, L. intermedia, Olea europea and Tetradenia riparia materials. With the exception of Ekebergia capensis and L. intermedia, there were no significant differences between the antioxidant activities of stored and fresh plant materials as measured in the β-carotene-linoleic acid model system. Similarly, the EC50 values based on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay were generally lower for stored than fresh material. Percentage inhibition of acetylcholinesterase was generally similar for both stored and fresh plant material. Stored plant material of Tetradenia riparia and Trichilia dregeana exhibited significantly higher AChE inhibition than the fresh material.The current study presents evidence that medicinal plants can retain their biological activity after prolonged storage under dark conditions at room temperature. The high antioxidant activities of stable bioactive compounds in these medicinal plants offer interesting prospects for the identification of novel principles for application in food and pharmaceutical formulations.
Anti-Oxidative and Cholinesterase Inhibitory Effects of Leaf Extracts and Their Isolated Compounds from Two Closely Related Croton Species
Ashwell R. Ndhlala,Mutalib A. Aderogba,Bhekumthetho Ncube,Johannes Van Staden
Molecules , 2013, DOI: 10.3390/molecules18021916
Abstract: A comparative evaluation of the antioxidant and acetylcholinesterase inhibitory activity of the leaf extracts of Croton gratissimus and Croton zambesicus ( subgratissimus) and compounds isolated from the extracts was carried out to determine their potential and suitability or otherwise as a substitute for each other in the management of oxidative and neurodegenerative conditions. Different antioxidant assays (DPPH, FRAP, β-carotene-linoleic and the lipid peroxidation models) and the microplate assay for acetylcholinesterase (AChE) inhibition were carried out separately to study the activities of the crude leaf extracts and four solvent fractions from each of the two Croton species. Bioassay guided fractionation was used to target antioxidant constituents of the crude extracts and ethyl acetate fractions of 20% aqueous methanol extract of C. gratissimus on silica gel and Sephadex LH-20 columns resulted in the isolation of kaempferol-3- O-β-6''(p-coumaroyl) glucopyranoside (tiliroside, 2), apigenin-6- C-glucoside (isovitexin, 3) and kampferol ( 4). The extract of C. zambesicus yielded quercetin-3- O-β-6''(p-coumaroyl) glucopyranoside-3'-methyl ether (helichrysoside- 3'-methyl ether, 1), kaempferol-3- O-β-6''(p-coumaroyl) glucopyranoside (tiliroside, 2) and apigenin-6- C-glucoside (isovitexin, 3). Three of the isolated compounds and their different combinations were also included in the bioassays. In all the assays performed, the antioxidant capacity and AChE inhibitory effects of C. zambesicus extracts were weaker than those of C. gratissimus. This suggests that C. gratissimus may not be substituted by C. zambesicus, despite the similarity in some of their constituents. Generally, the combinations made from the isolated compounds showed better activities in most of the assays compared to the individual isolated compounds. This suggests mechanisms such as synergism and/or additive effects to be taking place. This study established low, moderate and high antioxidant activities as well as AChE inhibitory effects by the crude extracts, fractions, compounds and compound combinations. This means some of the extracts, isolated compounds and compound combinations could be useful in the management of neurodegenerative conditions and serve as sources of natural neurodegenerative agents.
In Vitro Antimicrobial Activity of Extracts from Plants Used Traditionally in South Africa to Treat Tuberculosis and Related Symptoms
Balungile Madikizela,Ashwell Rungano Ndhlala,Jeffrey Franklin Finnie,Johannes Van Staden
Evidence-Based Complementary and Alternative Medicine , 2013, DOI: 10.1155/2013/840719
Antimicrobial and Selected In Vitro Enzyme Inhibitory Effects of Leaf Extracts, Flavonols and Indole Alkaloids Isolated from Croton menyharthii
Mutalib A. Aderogba,Ashwell R. Ndhlala,Kannan R. R. Rengasamy,Johannes Van Staden
Molecules , 2013, DOI: 10.3390/molecules181012633
Abstract: Croton species are used in folk medicine in the management of infections, inflammation and oxidative stress-related diseases. In order to isolate, characterize and evaluate the bioactive constituents of Croton menyharthii Pax leaf extracts, repeated column fractionation of the ethyl acetate fraction from a 20% aqueous methanol crude extract afforded three flavonols identified by NMR (1D and 2D) spectroscopic methods as myricetrin-3- O-rhamnoside (myricetrin, 1), quercetin-3- O-rhamnoside ( 2) and quercetin ( 3) along with an indole alkaloid, (E)- N-(4-hydroxycinnamoyl)-5-hydroxytryptamine, [ trans-N-( p-coumaroyl) serotonin, 4]. All the compounds are reported from the leaf extract of this plant for the first time. The crude extracts, four solvent fractions (hexane, DCM, ethyl acetate and butanol) and isolated compounds obtained from the leaves were evaluated for their inhibitory effects on selected bacteria, a fungus ( Candida albicans), cyclooxygenase (COX-2), α-glucosidase and acetylcholinesterase (AChE). Amongst the compounds, quercetin ( 3) was the most active against Bacillus subtilis and Candida albicans while myricetrin-3- O-rhamnoside ( 1) and trans-N-( p-coumaroyl) serotonin ( 4) were the most active compounds against Escherichia coli, Klebsiella pneumonia and Staphylococcus aureus. The inhibitory activity of myricetrin-3- O-rhamnoside ( 1) against COX-2 was insignificant while that of the other three compounds 2– 4 was low. The AChE inhibitory activity of the alkaloid, trans- N-( p-coumaroyl) serotonin was high, with a percentage inhibitory activity of 72.6% and an IC 50 value of 15.0 μg/mL. The rest of the compounds only had moderate activity. Croton menyharthii leaf extracts and isolated compounds inhibit α-glucosidase at very low IC 50 values compared to the synthetic drug acarbose. Structure activity relationship of the isolated flavonols 1– 3 is briefly outlined. Compounds 1– 4 and the leaf extracts exhibited a broad spectrum of activities. This validates the ethnomedicinal use of the plant in folk medicine.
Amides from Piper capense with CNS Activity – A Preliminary SAR Analysis
Mikael E. Pedersen,Bj?rn Metzler,Gary I. Stafford,Johannes Van Staden,Anna K. J?ger,Hasse B. Rasmussen
Molecules , 2009, DOI: 10.3390/molecules14093833
Abstract: Piper capense L.f. (Piperaceae) is used traditionally in South Africa as a sleep inducing remedy. Bioassay-guided fractionation of the roots of P. capense led to the isolation of piperine (1) and 4,5-dihydropiperine (2), which showed moderate affinity for the benzodiazepine site on the GABAA receptor (IC50 values of 1.2 mM and 1.0 mM, respectively). The present study suggests that strict structural properties of the amides are essential for affinity. Taken together, these observations suggest that the carbon chain must contain not less than four carbons, and that a conjugated double bond, adjacent to the amide group, is necessary for binding to the receptor and that the amine part should be bulky.
Transcriptome analysis of germinating maize kernels exposed to smoke-water and the active compound KAR1
Vilmos Soós, Endre Sebestyén, Angéla Juhász, Marnie E Light, Ladislav Kohout, Gabriella Szalai, Júlia Tandori, Johannes Van Staden, Ervin Balázs
BMC Plant Biology , 2010, DOI: 10.1186/1471-2229-10-236
Abstract: In this paper we demonstrate that although smoke-water and KAR1 treatment of maize kernels result in a similar physiological response, the gene expression and the protein ubiquitination patterns are quite different. Treatment with smoke-water enhanced the ubiquitination of proteins and activated protein-degradation-related genes. This effect was completely absent from KAR1-treated kernels, in which a specific aquaporin gene was distinctly upregulated.Our findings indicate that the array of bioactive compounds present in smoke-water form an environmental signal that may act together in germination stimulation. It is highly possible that the smoke/KAR1 'signal' is perceived by a receptor that is shared with the signal transduction system implied in perceiving environmental cues (especially stresses and light), or some kind of specialized receptor exists in fire-prone plant species which diverged from a more general one present in a common ancestor, and also found in non fire-prone plants allowing for a somewhat weaker but still significant response. Besides their obvious use in agricultural practices, smoke and KAR1 can be used in studies to gain further insight into the transcriptional changes during germination.Smoke released by natural fires is a major environmental cue in fire-prone habitats and a wide range of species show enhanced germination responses after exposure to aerosol smoke or smoke-water. In addition, several species from non-fire prone regions, and some major crops respond to various smoke treatments. Smoke can also positively affect the post-germination stage resulting in increased seedling vigour [1]. Efforts to identify the active compound from smoke-water resulted in the characterization of 3-methyl-2H-furo[2,3-c]pyran-2-one using achenes of Lactuca sativa cv. Grand Rapids [2] or the seeds of Conostylis aculeata and Stylidium affine [3] as germination test systems. This butenolide-type compound promotes germination over a very wide range of conce
Can involuntarily admitted patients give informed consent to participation in research?
CW van Staden
South African Journal of Psychiatry , 2007,
Improving the spelling ability of Grade 3 learners through visual imaging teaching strategies
Annalene van Staden
Per Linguam : A Journal of Language Learning , 2011, DOI: 10.5785/26-1-11
Abstract: This paper discusses two key cognitive theories underlying spelling acquisition, i.e. the developmental stage theory and the overlapping waves theory. Within the developmental stage framework, learning to spell is viewed as a process of moving from spelling that represents sound to spelling that represents meaning, following a sequence of qualitatively distinct stages in a linear fashion. In contrast, proponents of the overlapping waves theory emphasise the use of different instructional approaches at any given time. This model is process-orientated and stresses the adaptation of strategies to meet the needs of the task. Other researchers maintain that spelling is a natural process and emphasise the importance of invented spelling practices and creative writing embedded in whole-language programmes. There is, however, a lack of research validating the efficacy of an exclusively naturalistic approach to spelling. In general, research findings support a combination of incidental learning and direct instruction as most beneficial for learners with spelling problems. Thus, this study was undertaken to develop a visual imagery programme for Grade 3 learners by compromising between direct instruction in specific spelling skills (i.e. visual imaging strategies) whilst also immersing learners in meaningful authentic reading activities. It was hypothesised that the spelling abilities of Afrikaans-speaking Grade 3 learners can be improved significantly by exposing them to a spelling programme that focuses on visual imaging, immediate feedback and self-correcting strategies. Researchers opposed to visual teaching methods for spelling moreover postulate, among other things, that learners with auditory preferences will not benefit from a visual approach to the teaching of spelling. In this empirical study the possible relation between preferential learning styles and spelling performance was also investigated.
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