12 results on '"Viljoen AM"'
Search Results
2. Cyclooxygenase inhibitory activity of Aloe species
- Author
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Lindsey, KL, Jäger, Anna, Viljoen, AM, Lindsey, KL, Jäger, Anna, and Viljoen, AM
- Published
- 2002
3. Investigating the Antituberculosis Activity of Selected Commercial Essential Oils and Identification of Active Constituents Using a Biochemometrics Approach and In Silico Modeling.
- Author
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Boussamba-Digombou KJ, Sandasi M, Kamatou GP, van Vuuren S, Sawicki R, Fakhar Z, and Viljoen AM
- Abstract
Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis which has become prevalent due to the emergence of resistant M. tuberculosis strains. The use of essential oils (EOs) as potential anti-infective agents to treat microbial infections, including TB, offers promise due to their long historical use and low adverse effects. The current study aimed to investigate the in vitro anti-TB activity of 85 commercial EOs, and identify compounds responsible for the activity, using a biochemometrics approach. A microdilution assay was used to determine the antimycobacterial activity of the EOs towards some non-pathogenic Mycobacterium strains. In parallel, an Alamar blue assay was used to investigate antimycobacterial activity towards the pathogenic M. tuberculosis strain. Chemical profiling of the EOs was performed using gas chromatography-mass spectrometry (GC-MS) analysis. Biochemometrics filtered out putative biomarkers using orthogonal projections to latent structures discriminant analysis (OPLS-DA). In silico modeling was performed to identify potential therapeutic targets of the active biomarkers. Broad-spectrum antimycobacterial activity was observed for Cinnamomum zeylanicum (bark) (MICs = 1.00, 0.50, 0.25 and 0.008 mg/mL) and Levisticum officinale (MICs = 0.50, 0.5, 0.5 and 0.004 mg/mL) towards M. smegmatis , M. fortuitum , M. gordonae and M. tuberculosis , respectively. Biochemometrics predicted cinnamaldehyde, thymol and eugenol as putative biomarkers. Molecular docking demonstrated that cinnamaldehyde could serve as a scaffold for developing a novel class of antimicrobial compounds by targeting FtsZ and PknB from M. tuberculosis .
- Published
- 2022
- Full Text
- View/download PDF
4. Optimization of Antioxidant Synergy in a Polyherbal Combination by Experimental Design.
- Author
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Mapeka TM, Sandasi M, Viljoen AM, and van Vuuren SF
- Subjects
- Methanol, Plant Extracts pharmacology, Research Design, Antioxidants pharmacology, Oils, Volatile pharmacology
- Abstract
Culinary herbs and spices are known to be good sources of natural antioxidants. Although the antioxidant effects of individual culinary herbs and spices are widely reported, little is known about their effects when used in combination. The current study was therefore undertaken to compare the antioxidant effects of crude extracts and essential oils of some common culinary herbs and spices in various combinations. The antioxidant interactions of 1:1 combinations of the most active individual extracts and essential oils were investigated as well as the optimization of various ratios using the design of experiments (DoE) approach. The 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays were used to determine the antioxidant activity, and MODDE 9.1
® software (Umetrics AB, Umea, Sweden) was used to determine the DoE. The results revealed synergism for the following combinations: Mentha piperita with Thymus vulgaris methanol extract (ΣFIC = 0.32 and ΣFIC = 0.15 using the DPPH and FRAP assays, respectively); Rosmarinus officinalis with Syzygium aromaticum methanol extract (ΣFIC = 0.47 using the FRAP assay); T. vulgaris with Zingiber officinalis methanol extracts (ΣFIC = 0.19 using the ABTS assay); and R. officinalis with Z. officinalis dichloromethane extract (ΣFIC = 0.22 using the ABTS assay). The DoE produced a statistically significant (R2 = 0.905 and Q2 = 0.710) model that was able to predict extract combinations with high antioxidant activities, as validated experimentally. The antioxidant activities of the crude extracts from a selection of culinary herbs and spices were improved when in combination, hence creating an innovative opportunity for the future development of supplements for optimum health.- Published
- 2022
- Full Text
- View/download PDF
5. Phytochemical Profiling and Quality Control of Terminalia sericea Burch. ex DC. Using HPTLC Metabolomics.
- Author
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Mulaudzi N, Anokwuru CP, Tankeu SY, Combrinck S, Chen W, Vermaak I, and Viljoen AM
- Subjects
- Chromatography, High Pressure Liquid methods, Chromatography, Thin Layer methods, Metabolome, Phytochemicals isolation & purification, Plant Extracts chemistry, Plant Extracts isolation & purification, Plant Extracts metabolism, Quality Control, South Africa, Terminalia classification, Phytochemicals analysis, Phytochemicals metabolism, Terminalia chemistry, Terminalia metabolism
- Abstract
Terminalia sericea is used throughout Africa for the treatment of a variety of conditions and has been identified as a potential commercial plant. The study was aimed at establishing a high-performance thin layer chromatography (HPTLC) chemical fingerprint for T. sericea root bark as a reference for quality control and exploring chemical variation within the species using HPTLC metabo3lomics. Forty-two root bark samples were collected from ten populations in South Africa and extracted with dichloromethane: methanol (1:1). An HPTLC method was optimized to resolve the major compounds from other sample components. Dichloromethane: ethyl acetate: methanol: formic acid (90:10:30:1) was used as the developing solvent and the plates were visualized using 10% sulfuric acid in methanol as derivatizing agent. The concentrations of three major bioactive compounds, sericic acid, sericoside and resveratrol-3- O - β -rutinoside, in the extracts were determined using a validated ultra-performance liquid chromatography-photodiode array (UPLC-PDA) detection method. The rTLC software (written in the R-programming language) was used to select the most informative retardation factor (R f ) ranges from the images of the analysed sample extracts. Further chemometric models, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), were constructed using the web-based high throughput metabolomic software. The rTLC chemometric models were compared with the models previously obtained from ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). A characteristic fingerprint containing clear bands for the three bioactive compounds was established. All three bioactive compounds were present in all the samples, although their corresponding band intensities varied. The intensities correlated with the UPLC-PDA results, in that samples containing a high concentration of a particular compound, displayed a more intense band. Chemometric analysis using HCA revealed two chemotypes, and the subsequent construction of a loadings plot indicated that sericic acid and sericoside were responsible for the chemotypic variation; with sericoside concentrated in Chemotype 1, while sericic acid was more abundant in Chemotype 2. A characteristic chemical fingerprint with clearly distinguishable features was established for T. sericea root bark that can be used for species authentication, and to select samples with high concentrations of a particular marker compound(s). Different chemotypes, potentially differing in their therapeutic potency towards a particular target, could be distinguished. The models revealed the three analytes as biomarkers, corresponding to results reported for UPLC-MS profiling and thereby indicating that HPTLC is a suitable technique for the quality control of T. sericea root bark.
- Published
- 2021
- Full Text
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6. The Influence of Carrier Oils on the Antimicrobial Activity and Cytotoxicity of Essential Oils.
- Author
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Orchard A, Kamatou G, Viljoen AM, Patel N, Mawela P, and van Vuuren SF
- Abstract
The topical use of essential oils requires dilution into a carrier oil; however, scientific evidence regarding the antimicrobial efficacy and cytotoxicity when a carrier oil is combined with an essential oil is lacking. This study sets out to determine the antimicrobial activity and cytotoxicity of 23 essential oils combined with six known carrier oils. Gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID) was used to characterize the methyl esters of the carrier oils. The antimicrobial activity of the carrier oils alone and in combination with the essential oils was investigated using the broth microdilution assay against 11 skin pathogens and the cytotoxicity was determined using the brine shrimp lethality assay. The interactive profiles of the combinations for both antimicrobial activity and the cytotoxicity were analysed and calculated using the fractional inhibitory concentration index (ΣFIC). The carrier oils demonstrated no antimicrobial antagonism when combined with the essential oils and the overall cytotoxicity of the majority of the combinations was decreased. The carrier oils that could be identified as enhancing the antimicrobial activity and decreasing the cytotoxicity were Aloe vera Mill. and Simmondsia chinensis C.K.Schneid (Jojoba oil), with an overall reduction in essential oil cytotoxicity of 87.5% at 24 hrs and 85% at 48 hrs by A. vera . Five of the essential oils (when diluted in A. vera and S. chinensis carrier oils) demonstrated enhanced antimicrobial activity against pathogens such as Brevibacterium epidermidis , B. linens, and P. aeruginosa with MIC values ranging from 0.09 to 0.50 mg/mL (and ΣFIC 0.14-0.39). The study could conclude that the carrier oils are complementary to essential oil formulations, mostly reducing cytotoxicity and in some cases enhancing the antimicrobial activity.
- Published
- 2019
- Full Text
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7. Hyperspectral imaging and chemometric modeling of echinacea - a novel approach in the quality control of herbal medicines.
- Author
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Sandasi M, Vermaak I, Chen W, and Viljoen AM
- Subjects
- Chromatography, Liquid, Mass Spectrometry, Principal Component Analysis, Spectroscopy, Near-Infrared, Echinacea chemistry, Herbal Medicine, Models, Chemical, Quality Control
- Abstract
Echinacea species are popularly included in various formulations to treat upper respiratory tract infections. These products are of commercial importance, with a collective sales figure of $132 million in 2009. Due to their close taxonomic alliance it is difficult to distinguish between the three Echinacea species and incidences of incorrectly labeled commercial products have been reported. The potential of hyperspectral imaging as a rapid quality control method for raw material and products containing Echinacea species was investigated. Hyperspectral images of root and leaf material of authentic Echinacea species (E. angustifolia, E. pallida and E. purpurea) were acquired using a sisuChema shortwave infrared (SWIR) hyperspectral pushbroom imaging system with a spectral range of 920-2514 nm. Principal component analysis (PCA) plots showed a clear distinction between the root and leaf samples of the three Echinacea species and further differentiated the roots of different species. A classification model with a high coefficient of determination was constructed to predict the identity of the species included in commercial products. The majority of products (12 out of 20) were convincingly predicted as containing E. purpurea, E. angustifolia or both. The use of ultra performance liquid chromatography-mass spectrometry (UPLC-MS) in the differentiation of the species presented a challenge due to chemical similarities between the solvent extracts. The results show that hyperspectral imaging is an objective and non-destructive quality control method for authenticating raw material.
- Published
- 2014
- Full Text
- View/download PDF
8. Eugenol--from the remote Maluku Islands to the international market place: a review of a remarkable and versatile molecule.
- Author
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Kamatou GP, Vermaak I, and Viljoen AM
- Subjects
- Agrochemicals chemistry, Agrochemicals pharmacology, Analgesics chemistry, Analgesics pharmacology, Anti-Infective Agents chemistry, Anti-Infective Agents pharmacology, Anti-Inflammatory Agents chemistry, Anti-Inflammatory Agents pharmacology, Antimutagenic Agents chemistry, Antimutagenic Agents pharmacology, Antineoplastic Agents chemistry, Antineoplastic Agents pharmacology, Antioxidants chemistry, Antioxidants pharmacology, Eugenol chemistry, Eugenol immunology, Eugenol toxicity, Immunologic Factors chemistry, Immunologic Factors pharmacology, Eugenol pharmacology
- Abstract
Eugenol is a major volatile constituent of clove essential oil obtained through hydrodistillation of mainly Eugenia caryophyllata (=Syzygium aromaticum) buds and leaves. It is a remarkably versatile molecule incorporated as a functional ingredient in numerous products and has found application in the pharmaceutical, agricultural, fragrance, flavour, cosmetic and various other industries. Its vast range of pharmacological activities has been well-researched and includes antimicrobial, anti-inflammatory, analgesic, anti-oxidant and anticancer activities, amongst others. In addition, it is widely used in agricultural applications to protect foods from micro-organisms during storage, which might have an effect on human health, and as a pesticide and fumigant. As a functional ingredient, it is included in many dental preparations and it has also been shown to enhance skin permeation of various drugs. Eugenol is considered safe as a food additive but due to the wide range of different applications, extensive use and availability of clove oil, it is pertinent to discuss the general toxicity with special reference to contact dermatitis. This review summarises the pharmacological, agricultural and other applications of eugenol with specific emphasis on mechanism of action as well as toxicity data.
- Published
- 2012
- Full Text
- View/download PDF
9. In vitro transport of the steroidal glycoside P57 from Hoodia gordonii across excised porcine intestinal and buccal tissue.
- Author
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Vermaak I, Viljoen AM, Chen W, and Hamman JH
- Subjects
- Animals, Biological Transport, Carbohydrate Sequence, Cell Membrane Permeability, Molecular Sequence Data, Mouth Mucosa drug effects, Plants, Medicinal chemistry, Swine, Apocynaceae chemistry, Glycosides pharmacokinetics, Intestinal Mucosa metabolism, Plant Extracts pharmacokinetics
- Abstract
Hoodia gordonii was traditionally used by the Khoisan people as a thirst and appetite suppressant and is currently commercially available as a popular weight-loss supplement. The perceived active ingredient isolated from this plant is a steroidal glycoside named P57. This study aimed at investigating the in vitro transport of P57 across excised porcine intestinal and buccal mucosa in a Sweetana-Grass diffusion apparatus. For both the intestinal and buccal experiments, the transport of pure P57 was compared to that obtained from a crude plant extract. Bi-directional transport experiments were conducted across the intestinal tissue in two different media namely Krebs-Ringer bicarbonate buffer and simulated intestinal fluid. Apical-to-basolateral transport experiments were conducted across the buccal tissue in two different media namely Krebs-Ringer bicarbonate buffer and artificial saliva. Apparent permeability coefficient (P(app)) and flux values were calculated and analysed by means of a one-way repeated analysis of variance (ANOVA) to determine if differences were significant (p≤0.05). The transport of pure P57 across intestinal tissue was significantly higher in the secretory direction than in the absorptive direction indicating efflux by membrane transporters. Much higher intestinal transport was obtained for P57 in both directions when applied in the form of a crude extract, possibly due to inhibition of efflux as indicated by lower secretory transport compared to absorptive transport. For the buccal tissue, no transport was obtained for the pure P57, while relatively high transport was obtained when applied in the form of a crude extract. Furthermore, the intestinal transport of P57 was significantly decreased when the crude extract was prepared in simulated intestinal fluid compared to when it was prepared in buffer. On the other hand, buccal transport was higher in artificial saliva than in buffer. It is therefore evident that the transport of P57 across mucosal tissues is significantly affected on exposure to conditions simulating the in vivo situation., (Copyright © 2011 Elsevier GmbH. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
10. Polymeric plant-derived excipients in drug delivery.
- Author
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Beneke CE, Viljoen AM, and Hamman JH
- Subjects
- Polymers isolation & purification, Drug Delivery Systems, Plants chemistry, Polymers chemistry
- Abstract
Drug dosage forms contain many components in addition to the active pharmaceutical ingredient(s) to assist in the manufacturing process as well as to optimise drug delivery. Due to advances in drug delivery technology, excipients are currently included in novel dosage forms to fulfil specific functions and in some cases they directly or indirectly influence the extent and/or rate of drug release and absorption. Since plant polysaccharides comply with many requirements expected of pharmaceutical excipients such as non-toxicity, stability, availability and renewability they are extensively investigated for use in the development of solid oral dosage forms. Furthermore, polysaccharides with varying physicochemical properties can be extracted from plants at relatively low cost and can be chemically modified to suit specific needs. As an example, many polysaccharide-rich plant materials are successfully used as matrix formers in modified release dosage forms. Some natural polysaccharides have even shown environmental-responsive gelation characteristics with the potential to control drug release according to specific therapeutic needs. This review discusses some of the most important plant-derived polymeric compounds that are used or investigated as excipients in drug delivery systems.
- Published
- 2009
- Full Text
- View/download PDF
11. Interconvertions between delta-lactam and delta-lactone derivatives initiated by unique transannular interactions of the rigid cyclohexane boat structure in pentacycloundecane.
- Author
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Kruger HG, Martins FJ, and Viljoen AM
- Subjects
- Catalysis, Molecular Conformation, Molecular Structure, Stereoisomerism, Cyclohexanes chemistry, Lactams chemistry, Lactones chemistry
- Abstract
The pentacycloundecane (PCU) cage structure resembles a perfect boat conformation, and for the first time unique lactam/lactone interconversions on the flagpole carbons of a cyclohexane boat structure are reported. The syntheses of a novel dihydroxy-PCU-delta-lactone and two novel N-substituted PCU-delta-lactams are reported. Hydrolysis of some of the PCU-delta-lactam compounds produced delta-lactones, and reaction of the lactones with ammonia or primary amines again produced delta-lactams. Reaction mechanisms to account for the unusual interconversion reactions induced by transannular interactions are proposed.
- Published
- 2004
- Full Text
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12. Experimental design for the formulation and optimization of novel cross-linked oilispheres developed for in vitro site-specific release of Mentha piperita oil.
- Author
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Sibanda W, Pillay V, Danckwerts MP, Viljoen AM, van Vuuren S, and Khan RA
- Subjects
- Drug Carriers, Microspheres, Chemistry, Pharmaceutical, Drug Delivery Systems, Mentha piperita chemistry, Oils administration & dosage
- Abstract
A Plackett-Burman design was employed to develop and optimize a novel crosslinked calcium-aluminum-alginate-pectinate oilisphere complex as a potential system for the in vitro site-specific release of Mentha piperita, an essential oil used for the treatment of irritable bowel syndrome. The physicochemical and textural properties (dependent variables) of this complex were found to be highly sensitive to changes in the concentration of the polymers (0%-1.5% wt/vol), crosslinkers (0%-4% wt/vol), and crosslinking reaction times (0.5-6 hours) (independent variables). Particle size analysis indicated both unimodal and bimodal populations with the highest frequency of 2 mm oilispheres. Oil encapsulation ranged from 6 to 35 mg/100 mg oilispheres. Gravimetric changes of the crosslinked matrix indicated significant ion sequestration and loss in an exponential manner, while matrix erosion followed Higuchi's cube root law. Among the various measured responses, the total fracture energy was the most suitable optimization objective (R2 = 0.88, Durbin-Watson Index = 1.21%, Coefficient of Variation (CV) = 33.21%). The Lagrangian technique produced no significant differences (P > .05) between the experimental and predicted total fracture energy values (0.0150 vs 0.0107 J). Artificial Neural Networks, as an alternative predictive tool of the total fracture energy, was highly accurate (final mean square error of optimal network epoch approximately 0.02). Fused-coated optimized oilispheres produced a 4-hour lag phase followed by zero-order kinetics (n > 0.99), whereby analysis of release data indicated that diffusion (Fickian constant k1 = 0.74 vs relaxation constant k2 = 0.02) was the predominant release mechanism.
- Published
- 2004
- Full Text
- View/download PDF
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