Search Results (6)

Herbal teas are used in South Africa as digestives to lower glycaemia and for other indications. However, the chemical composition of the infusions and their effect on enzymes related to metabolic syndrome is poorly known. The composition of infusions and methanol extracts of B. saligna (Scrophulariaceae), Lippia javanica, L. scaberrima, and Phyla dulcis (Verbenaceae) was assessed and the effect of the infusions and extract was determined towards α-glucosidase, α-amylase, and pancreatic lipase. The commercial herbal products were extracted separately with MeOH or hot water to obtain the extract/infusion for comparative studies. Total phenolic, total flavonoid and antioxidant capacity were assessed. The fingerprints of the MeOH extracts and infusions were compared by HPLD-DAD. The extract constituents were tentatively identified by HPLC-MS/MS and NMR analyses. From the extracts/infusions, 57 compounds were identified, including iridoids, phenylpropanoid glycosides, flavonoids, and caffeic acid derivatives, among others. The MeOH extracts and infusions showed strong inhibition towards α-glucosidase with IC₅₀ in the range of 0.13–0.84 µg/mL for the phenolic-enriched infusion extract (PEI) and 0.47–0.50 µg/mL for the MeOH extracts, respectively. The P. dulcis PEI showed higher inhibition towards α-glucosidase, and the MeOH extract of L. scaberrima was better than the PEI. At 100 µg/mL, the PEI from the four herbal teas reduces the activity of α-amylase by 23.03–28.61%, with L. javanica as the most active tea. Three of the species are high in phenylpropanoid glycosides, while P. dulcis contains rosmarinic acid. Some 26 compounds were identified in the infusion from B. saligna, 28 from L. scaberrima, and 21 from P. dulcis. Four of them are common in all the teas, namely decaffeoylverbascoside, verbascoside, isoverbascoside, and tuberonic acid hexoside. Ten compounds occur in two of the teas and seventeen, fifteen, and eleven compounds were detected only in B. saligna, L. scaberrima, and P. dulcis, respectively. Most of the compounds are reported for the first time from the crude drug infusions. The results give some support for the traditional use of herbal teas as digestives and/or indications for diabetes. The chemical fingerprints set the basis for quality control of the crude drugs, based on the main constituents and differential compounds occurring in the samples. Full article

South Africa is home to a variety of herbal teas, such as bush tea (Athrixia phylicoides DC.), honeybush tea (Cyclopia intermedia E. Mey and C. subternata Vogel), special tea (Monsonia burkeana Planch. ex Harv.), and rooibos tea (Aspalathus linearis (Burm.f.) R. Dahlgren) that are known to possess anti-oxidant, anti-inflammatory and anti-diabetic properties. The objective of this study was to determine the in vitro anti-oxidant activity of selected tea blends using 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays, as well as to assess their anti-inflammatory properties using the 15-lipoxygenase inhibitory assay. Furthermore, the study measured glucose utilisation in C2C12 myotubes. Lastly, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was used to test the safety of the tea extracts on Vero cells (African green monkey kidney cell line). Special tea and its blend with bush tea exhibited potent anti-oxidant and anti-inflammatory activity. The blending of bush tea with special tea at different ratios resulted in increased anti-oxidant activity. Although special tea had a level of cell toxicity, its toxicity was lowered during blending. All of the tea samples showed anti-diabetic effects, although with less potency as compared to insulin. The current investigation supports the use of blended herbal teas, and the positive anti-inflammatory effect of special tea warrants further research. Full article

Aspalathus linearis (Burm.f.) R. Dahlgren, commonly known as rooibos tea, was consumed traditionally by the indigenous South African inhabitants as an herbal remedy. Beside antioxidant properties, it displays antiallergic, antispasmodic, and hypoglycemic activities. An ultra-high-performance liquid chromatography method coupled with photodiode array and mass spectrometry detectors were developed for the determination of 14 phenolic constituents from leaves and stems of A. linearis. The efficient separation was performed within 30 min at a temperature of 30 °C by using C-18 column as the stationary phase and water/acetonitrile with 0.05% formic acid as the mobile phase. Method validation for linearity, repeatability, limits of detection, and limits of quantification was achieved. The limits of detection from 0.2–1 μg/mL were reported for the standard compounds. Their total content varied substantially (1.50–9.85 mg/100 mg sample) in 21 dietary supplements. The presence of regioisomers and diastereomers which co-elute on a variety of stationary phases make separation for quantification purposes challenging. This method was found to be efficient in providing low retention times and excellent resolution for this type of phytochemicals. The established method is suitable for chemical fingerprint analysis of A. linearis and cost-effective for quality control of rooibos tea products. Full article

Rooibos (Aspalathus linearis), widely known as a herbal tea, is endemic to the Cape Floristic Region of South Africa (SA). It produces a wide range of phenolic compounds that have been associated with diverse health promoting properties of the plant. The species comprises several growth forms that differ in their morphology and biochemical composition, only one of which is cultivated and used commercially. Here, we established methodologies for non-invasive transcriptome research of wild-growing South African plant species, including (1) harvesting and transport of plant material suitable for RNA sequencing; (2) inexpensive, high-throughput biochemical sample screening; (3) extraction of high-quality RNA from recalcitrant, polysaccharide- and polyphenol rich plant material; and (4) biocomputational analysis of Illumina sequencing data, together with the evaluation of programs for transcriptome assembly (Trinity, IDBA-Trans, SOAPdenovo-Trans, CLC), protein prediction, as well as functional and taxonomic transcript annotation. In the process, we established a biochemically characterized sample pool from 44 distinct rooibos ecotypes (1–5 harvests) and generated four in-depth annotated transcriptomes (each comprising on average ≈86,000 transcripts) from rooibos plants that represent distinct growth forms and differ in their biochemical profiles. These resources will serve future rooibos research and plant breeding endeavours. Full article

Bush tea (Athrixia phylicoides DC.) is a South African indigenous herbal tea rich in secondary metabolites with medicinal significance. However, studies on the effects of seasonal changes on bush tea and quantification of its metabolites using untargeted approach have not been explored. Therefore, this study’s objective was to investigate the effects of seasonal variation on the metabolites of bush tea using LC-MS/MS (Liquid Chromatography with Tandem Mass Spectrometry) and ¹H NMR (High-Resolution Proton Nuclear Magnetic Resonance) techniques. Bush tea leaves were plucked once in each season namely, autumn (March to May), winter (June to August), spring (September to November), and summer (December to February). The primary metabolites including non-essential amino acids, organic acids, and vitamins in bush tea were predominantly elevated during summer and spring. The ¹H NMR-based metabolomic analysis revealed that bush tea metabolome was strongly affected by seasonal variations, using the partial least squares-discriminant analysis (PLS-DA) which demonstrated four distinct groups of seasons. Similarly, the ¹H NMR based metabolic profiling of bush tea subjected to different seasons resulted in putative annotation of six phenolic compounds which included rutin, 4-(hydroxyphenyl) propyl coumarate, caffeic acid, hymenoxin, quercetin, and kaempferol. The phenolics and primary metabolites differed remarkably per season with enhanced accumulation observed in the summer and spring harvested bush tea. The LC-MS and ¹H NMR metabolomics analysis suggests that summer and spring can be recommended as preferred plucking seasons for bush tea leaves and twigs. Full article

Cyclopia subternata plants are traditionally used for the production of the South African herbal tea, honeybush, and recently as aqueous extracts for the food industry. A C. subternata aqueous extract and mangiferin (a major constituent) are known to have anti-diabetic properties. Variation in phenolic composition and antioxidant capacity is expected due to cultivation largely from seedlings, having implications for extract standardization and quality control. Aqueous extracts from 64 seedlings of the same age, cultivated under the same environmental conditions, were analyzed for individual compound content, total polyphenol (TP) content and total antioxidant capacity (TAC) in a number of assays. An HPLC method was developed and validated to allow quantification of xanthones (mangiferin, isomangiferin), flavanones (hesperidin, eriocitrin), a flavone (scolymoside), a benzophenone (iriflophenone-3-C-β-glucoside) and dihydrochalcones (phloretin-3',5'-di-C-β-glucoside, 3-hydroxyphloretin-3',5'-di-C-hexoside). Additional compounds were tentatively identified using mass spectrometric detection, with the presence of the 3-hydroxyphloretin-glycoside, an iriflophenone-di-O,C-hexoside, an eriodictyol-di-C-hexoside and vicenin-2 being demonstrated for the first time. Variability of the individual phenolic compound contents was generally higher than that of the TP content and TAC values. Among the phenolic compounds, scolymoside, hesperidin and iriflophenone-3-C-β-glucoside contents were the most variable. A combination of the measured parameters could be useful in product standardization by providing a basis for specifying minimum levels. Full article