Models to predict the total antioxidant capacity (TAC) of rooibos tea infusions from their chromatographic fingerprints and peak table data (content of individual phenolic compounds), obtained using HPLC with diode array detection, were... more
Models to predict the total antioxidant capacity (TAC) of rooibos tea infusions from their chromatographic fingerprints and peak table data (content of individual phenolic compounds), obtained using HPLC with diode array detection, were developed in order to identify potential antioxidant markers. Peak table data included the content of 12 compounds, namely phenylpyruvic acid-2-O-glucoside, aspalathin, nothofagin, isoorientin, orientin, ferulic acid, quercetin-3-O-robinobioside, vitexin, hyperoside, rutin, isovitexin and isoquercitrin. The TAC values, measured using the oxygen radical absorbance capacity (ORAC) and DPPH radical scavenging assays, could be predicted from the peak table data or the chromatographic fingerprints (prediction errors 9-12%) using partial least squares (PLS) regression. Prediction models created from samples of only two production years could additionally be used to predict the TAC of samples from another production year (prediction errors<13%) indicating the robustness of the models in a quality control environment. Furthermore, the uninformative variable elimination (UVE)-PLS method was used to identify potential antioxidant markers for rooibos infusions. All individual phenolic compounds that were quantified were selected as informative variables, except vitexin, while UVE-PLS models developed from chromatographic fingerprints indicated additional antioxidant markers, namely (S)-eriodictyol-6-C-glucoside, (R)-eriodictyol-6-C-glucoside, aspalalinin and two unidentified compounds. The potential antioxidant markers should be validated prior to use in quality control of rooibos tea.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Biochemical detection (BCD) methods are commonly used to screen plant extracts for specific biological activities in batch assays. Traditionally, bioactives in the most active extracts were identified through time-consuming bio-assay... more
Biochemical detection (BCD) methods are commonly used to screen plant extracts for specific biological activities in batch assays. Traditionally, bioactives in the most active extracts were identified through time-consuming bio-assay guided fractionation until single active compounds could be isolated. Not only are isolation procedures often tedious, but they could also lead to artifact formation. On-line coupling of BCD assays to high performance liquid chromatography (HPLC) is gaining ground as a high resolution screening technique to overcome problems associated with pre-isolation by measuring the effects of compounds post-column directly after separation. To date, several on-line HPLC-BCD assays, applied to whole plant extracts and mixtures, have been published. In this review the focus will fall on enzyme-based, receptor-based and antioxidant assays.
Research Interests: Engineering, Genetics, Technology, Drug Discovery, Enzyme Inhibitors, and 23 morePharmacognosy, Screening, Antioxidants, Humans, HPLC, Natural Product, Methanol, Oxidoreductases, Line Detection, High Performance Liquid Chromatography, Online Systems, High Pressure Liquid Chromatography, CHEMICAL SCIENCES, Molecular sciences, Plant extracts, Phytochemicals, Kava, Biological activity, Equipment Design, Ligands, Phytoestrogens, Metabolome, and Ocimum basilicum L.
Research Interests: Engineering, Technology, Natural Products Chemistry, NMR Spectroscopy, Flavonoids, and 16 moreAntioxidants, Polyphenols, HPLC, Iron, Asteraceae, South African, CHEMICAL SCIENCES, Antioxidant Activity, High Resolution, Phenolic compound, Plant extracts, Flavonoid and Phenolic Content, Chlorogenic Acid, Chemical Structure, Linoleic Acid, and Countercurrent chromatography
Aspalathin (2′, 3, 4, 4′, 6′-pentahydroxy-3′-C-β-d-glucopyranosyldihydrochalcone) is the major flavonoid present in the South African herbal tea rooibos. In vitro metabolism of aspalathin and a structural analogue nothofagin, lacking the... more
Aspalathin (2′, 3, 4, 4′, 6′-pentahydroxy-3′-C-β-d-glucopyranosyldihydrochalcone) is the major flavonoid present in the South African herbal tea rooibos. In vitro metabolism of aspalathin and a structural analogue nothofagin, lacking the A ring catechol group, was ...