Development of sensory tools for green rooibos (Aspalathus linearis (Burm.f.) R.Dahlgren) and changes in quality attributes during shelf-life storage.

BACKGROUND: Green rooibos (Aspalathus linearis (Burm.f.) R.Dahlgren) herbal tea is popular due to its health-promoting properties. Information on its characteristic sensory profile is scarce and sensory tools to define product variation are needed. The storage conditions and time during its shelf-life are hypothesized to affect the product quality. RESULTS: Production batches from two producers spanning 5 years (n = 57) were analyzed using descriptive sensory analysis. Primary attributes (>30 median intensity; 100% occurrence frequency) included 'hay/dried grass', 'cooked oats', 'tobacco', 'honey' and 'caramel' aromas, and astringent mouthfeel. 'Cooked vegetables', 'green grass', 'stewed fruit', 'rooibos-woody', 'marmalade' and 'cardboard' aromas, sweet taste and bitter taste were secondary attributes (10-20 median intensity; 100% occurrence frequency). The same flavor attributes were present, except for sweet-associated and fruity notes. A sensory lexicon and sensory wheels for aroma and palate attributes were constructed from the data. The shelf-life stability of green rooibos was evaluated in moisture-impermeable (pouches) and moisture-permeable (sachets) packaging at 25 and 40 °C at 60% relative humidity over 24 weeks. Green rooibos samples stored in pouches at 4 °C were also evaluated. Storage in sachets led to moisture uptake (~10 g (100 g)-1 dry basis) and an increase in water activity (>0.6), causing degradation of chlorophyll and dihydrochalcones. Changes in color and sensory profile (decreased vegetal, cereal and cardboard aromas and increased sweet-associated and fruity aromas) were evident and more pronounced at the higher storage temperature. CONCLUSIONS: Storage at ≤25 °C in moisture-impermeable packaging material is recommended for green rooibos herbal tea. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Aspalathin and Other Rooibos Flavonoids Trapped α-Dicarbonyls and Inhibited Formation of Advanced Glycation End Products In Vitro.

The excessive dietary intake of simple sugars and abnormal metabolism in certain diseases contribute to the increased production of α-dicarbonyls (α-DCs), such as methylglyoxal (MGO) and glyoxal (GO), the main precursors of the formation of advanced glycation end products (AGEs). AGEs play a vital role, for example, in the development of cardiovascular diseases and diabetes. Aspalathus linearis (Burman f.) R. Dahlgren (known as rooibos tea) exhibits a wide range of activities beneficial for cardio-metabolic health. Thus, the present study aims to investigate unfermented and fermented rooibos extracts and their constituents for the ability to trap MGO and GO. The individual compounds identified in extracts were tested for the capability to inhibit AGEs (with MGO or GO as a glycation agent). Ultra-high-performance liquid chromatography coupled with an electrospray ionization mass spectrometer (UHPLC-ESI-MS) was used to investigate α-DCs' trapping capacities. To evaluate the antiglycation activity, fluorescence measurement was used. The extract from the unfermented rooibos showed a higher ability to capture MGO/GO and inhibit AGE formation than did the extract from fermented rooibos, and this effect was attributed to a higher content of dihydrochalcones. The compounds detected in the extracts, such as aspalathin, nothofagin, vitexin, isovitexin, and eriodictyol, as well as structurally related phloretin and phloroglucinol (formed by the biotransformation of certain flavonoids), trapped MGO, and some also trapped GO. AGE formation was inhibited the most by isovitexin. However, it was the high content of aspalathin and its higher efficiency than that of metformin that determined the antiglycation and trapping properties of green rooibos. Therefore, A. linearis, in addition to other health benefits, could potentially be used as an α-DC trapping agent and AGE inhibitor.

Shelf-Life Stability of Ready-to-Use Green Rooibos Iced Tea Powder-Assessment of Physical, Chemical, and Sensory Properties.

Green rooibos extract (GRE), shown to improve hyperglycemia and HDL/LDL blood cholesterol, has potential as a nutraceutical beverage ingredient. The main bioactive compound of the extract is aspalathin, a C-glucosyl dihydrochalcone. The study aimed to determine the effect of common iced tea ingredients (citric acid, ascorbic acid, and xylitol) on the stability of GRE, microencapsulated with inulin for production of a powdered beverage. The stability of the powder mixtures stored in semi-permeable (5 months) and impermeable (12 months) single-serve packaging at 30 °C and 40 °C/65% relative humidity was assessed. More pronounced clumping and darkening of the powders, in combination with higher first order reaction rate constants for dihydrochalcone degradation, indicated the negative effect of higher storage temperature and an increase in moisture content when stored in the semi-permeable packaging. These changes were further increased by the addition of crystalline ingredients, especially citric acid monohydrate. The sensory profile of the powders (reconstituted to beverage strength iced tea solutions) changed with storage from a predominant green-vegetal aroma to a fruity-sweet aroma, especially when stored at 40 °C/65% RH in the semi-permeable packaging. The change in the sensory profile of the powder mixtures could be attributed to a decrease in volatile compounds such as 2-hexenal, (Z)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, (E,Z)-2,6-nonadienal and (E)-2-decenal associated with "green-like" aromas, rather than an increase in fruity and sweet aroma-impact compounds. Green rooibos extract powders would require storage at temperatures ≤ 30 °C and protection against moisture uptake to be chemically and physically shelf-stable and maintain their sensory profiles.

Rooibos Flavonoids, Aspalathin, Isoorientin, and Orientin Ameliorate Antimycin A-Induced Mitochondrial Dysfunction by Improving Mitochondrial Bioenergetics in Cultured Skeletal Muscle Cells.

The current study investigated the physiological effects of flavonoids found in daily consumed rooibos tea, aspalathin, isoorientin, and orientin on improving processes involved in mitochondrial function in C2C12 myotubes. To achieve this, C2C12 myotubes were exposed to a mitochondrial channel blocker, antimycin A (6.25 µM), for 12 h to induce mitochondrial dysfunction. Thereafter, cells were treated with aspalathin, isoorientin, and orientin (10 µM) for 4 h, while metformin (1 µM) and insulin (1 µM) were used as comparators. Relevant bioassays and real-time PCR were conducted to assess the impact of treatment compounds on some markers of mitochondrial function. Our results showed that antimycin A induced alterations in the mitochondrial respiration process and mRNA levels of genes involved in energy production. In fact, aspalathin, isoorientin, and orientin reversed such effects leading to the reduced production of intracellular reactive oxygen species. These flavonoids further enhanced the expression of genes involved in mitochondrial function, such as Ucp 2, Complex 1/3, Sirt 1, Nrf 1, and Tfam. Overall, the current study showed that dietary flavonoids, aspalathin, isoorientin, and orientin, have the potential to be as effective as established pharmacological drugs such as metformin and insulin in protecting against mitochondrial dysfunction in a preclinical setting; however, such information should be confirmed in well-established in vivo disease models.

Orientin Improves Substrate Utilization and the Expression of Major Genes Involved in Insulin Signaling and Energy Regulation in Cultured Insulin-Resistant Liver Cells.

Our group has progressively reported on the impact of bioactive compounds found in rooibos (Aspalathus linearis) and their capacity to modulate glucose homeostasis to improve metabolic function in experimental models of type 2 diabetes. In the current study, we investigated how the dietary flavone, orientin, modulates the essential genes involved in energy regulation to enhance substrate metabolism. We used a well-established hepatic insulin resistance model of exposing C3A liver cells to a high concentration of palmitate (0.75 mM) for 16 hrs. These insulin-resistant liver cells were treated with orientin (10 µM) for 3 h to assess the therapeutic effect of orientin. In addition to assessing the rate of metabolic activity, end point measurements assessed include the uptake or utilization of glucose and palmitate, as well as the expression of genes involved in insulin signaling and regulating cellular energy homeostasis. Our results showed that orientin effectively improved metabolic activity, mainly by maintaining substrate utilization which was marked by enhanced glucose and palmitate uptake by liver cells subjected to insulin resistance. Interestingly, these effects can be explained by the improvement in the expression of genes involved in glucose transport (Glut2), insulin signaling (Irs1 and Pi3k), and energy regulation (Ampk and Cpt1). These preliminary findings lay an important foundation for future research to determine the bioactive properties of orientin against dyslipidemia or insulin resistance in reliable and well-established models of type 2 diabetes.

Fumonisin B1 -induced mitochondrial toxicity and hepatoprotective potential of rooibos: An update.

Fumonisins are a family of potentially carcinogenic mycotoxins produced by Fusarium verticillioides. Several fumonisins have been identified with fumonisin B1 (FB1 ) being the most toxic. The canonical mechanism of FB1 toxicity is centered on its structural resemblance with sphinganine and consequent competitive inhibition of ceramide synthase and disruption of lipidomic profiles. Recent and emerging evidence at the molecular level has identified the disruption of mitochondria and excessive generation of toxic reactive oxygen species (ROS) as alternative/additional mechanisms of toxicity. The understanding of how these pathways contribute to FB1 toxicity can lead to the identification of novel, effective approaches to protecting vulnerable populations. Natural compounds with antioxidant properties seem to protect against the induced toxic effects of FB1 . Rooibos (Aspalathus linearis), endemic to South Africa, has traditionally been used as a medicinal herbal tea with strong scientific evidence supporting its anecdotal claims. The unique composition of phytochemicals and combination of metabolic activators, adaptogens and antioxidants make rooibos an attractive yet underappreciated intervention for FB1 toxicoses. In the search for a means to address FB1 toxicoses as a food safety problem in developing countries, phytomedicine and traditional knowledge systems must play an integral part. This review aims to summarize the growing body of evidence succinctly, which highlights mitochondrial dysfunction as a secondary toxic effect responsible for the FB1 -induced generation of ROS. We further propose the potential of rooibos to combat this induced toxicity based on its integrated bioactive properties, as a socio-economically viable strategy to prevent and/or repair cellular damage caused by FB1 .

Differential Modulation of Gene Expression Encoding Hepatic and Renal Xenobiotic Metabolizing Enzymes by an Aspalathin-Enriched Rooibos Extract and Aspalathin.

Modulation of the expression of hepatic and renal genes encoding xenobiotic metabolizing enzymes by an aspalathin-enriched green rooibos (Aspalathus linearis) extract (GRE) was investigated in the liver and kidneys of F344 rats following dietary exposure of 28 d, as well as selected xenobiotic metabolizing genes in rat primary hepatocytes. In the liver, GRE upregulated genes (p < 0.05) encoding aldehyde dehydrogenase, glucose phosphate isomerase, and cytochrome P450 while 17ß-hydroxysteroid dehydrogenase 2 (Hsd17ß2) was downregulated. In primary hepatocytes, GRE lacked any effect, while aspalathin downregulated Hsd17ß2, mimicking the effect of GRE in vivo, and upregulated catechol-O-methyl transferase and marginally (p < 0.1) cytochrome P450 2e1. In the kidneys, GRE upregulated (p < 0.05) genes encoding the phase II xenobiotic metabolism enzymes, glutathione-S-transferase mµ and microsomal glutathione-S-transferase, while downregulating genes encoding the ATP binding cassette transporter, cytochrome P450, gamma glutamyltransferase 1, and N-acetyltransferase 1. Differential modulation of the expression of xenobiotic metabolizing genes in vivo and in vitro by GRE is dose-related, duration of exposure, the tissue type, and interactions between specific polyphenol and/or combinations thereof. Aspalathin is likely to be responsible for the downregulation of estradiol and testosterone catabolism by GRE in the liver. The differential gene expression by GRE in the liver and kidneys could, depending on the duration exposure and dose utilized, determine the safe use of such an extract in humans for specific health and/or disease outcomes.

Rooibos tea (Aspalathus linearis) ameliorates the CCl4-induced injury to mitochondrial respiratory function and energy production in rat liver.

The rooibos tea (RT) is a source of valuable dietary dihydrochalcones  aspalathin, and nothofagin and other polyphenols. Many in vitro and in vivo studies have shown that RT flavonoids have strong antioxidant effect and significantly reduce oxidative stress. We investigated the antioxidant activity and protective effect of an aqueous extract of RT on the liver mitochondria oxidative phosphorylation in rats with carbon tetrachloride-induced (CCl4-induced) liver damage. Mitochondrial respiration and ATP production was determined amperometrically using a Clark-type oxygen electrode. We found significantly decreased parameters of oxidative phosphorylation in the group having received CCl4 for 10 weeks. Simultaneous administration of RT increased oxygen uptake stimulated with ADP, and the rate of ATP generation in the mitochondria of rats, both having been impaired in rats treated with CCl4 only. Treatment with RT significantly decreased CCl4-induced elevated enzyme levels, improved capacity of the respiratory chain and energy production, presumably due to its potent and direct antioxidant activity, including inhibition of mitochondrial lipid peroxidation. Improved histological features support the view of antioxidant and membrane-stabilizing activity of RT. This fact may play a significant role in the protection of the liver from injury caused by known toxins, and from subsequent development of steatosis and fibrosis..

Aspalathin-Enriched Green Rooibos Extract Reduces Hepatic Insulin Resistance by Modulating PI3K/AKT and AMPK Pathways.

We previously demonstrated that an aspalathin-enriched green rooibos extract (GRE) reversed palmitate-induced insulin resistance in C2C12 skeletal muscle and 3T3-L1 fat cells by modulating key effectors of insulin signalling such as phosphatidylinositol-4,5-bisphosphate 3-kinase/protein kinase B (PI3K/AKT) and AMP-activated protein kinase (AMPK). However, the effect of GRE on hepatic insulin resistance is unknown. The effects of GRE on lipid-induced hepatic insulin resistance using palmitate-exposed C3A liver cells and obese insulin resistant (OBIR) rats were explored. GRE attenuated the palmitate-induced impairment of glucose and lipid metabolism in treated C3A cells and improved insulin sensitivity in OBIR rats. Mechanistically, GRE treatment significantly increased PI3K/AKT and AMPK phosphorylation while concurrently enhancing glucose transporter 2 expression. These findings were further supported by marked stimulation of genes involved in glucose metabolism, such as insulin receptor (Insr) and insulin receptor substrate 1 and 2 (Irs1 and Irs2), as well as those involved in lipid metabolism, including Forkhead box protein O1 (FOXO1) and carnitine palmitoyl transferase 1 (CPT1) following GRE treatment. GRE showed a strong potential to ameliorate hepatic insulin resistance by improving insulin sensitivity through the regulation of PI3K/AKT, FOXO1 and AMPK-mediated pathways.

Visualization of Aspalathin in Rooibos (Aspalathus linearis) Plant and Herbal Tea Extracts Using Thin-Layer Chromatography.

Aspalathin, the main polyphenol of rooibos (Aspalathus linearis), is associated with diverse health promoting properties of the tea. During fermentation, aspalathin is oxidized and concentrations are significantly reduced. Standardized methods for quality control of rooibos products do not investigate aspalathin, since current techniques of aspalathin detection require expensive equipment and expertise. Here, we describe a simple and fast thin-layer chromatography (TLC) method that can reproducibly visualize aspalathin in rooibos herbal tea and plant extracts at a limit of detection (LOD) equal to 178.7 ng and a limit of quantification (LOQ) equal to 541.6 ng. Aspalathin is a rare compound, so far only found in A. linearis and its (rare) sister species A. pendula. Therefore, aspalathin could serve as a marker compound for authentication and quality control of rooibos products, and the described TLC method represents a cost-effective approach for high-throughput screening of plant and herbal tea extracts.

Rooibos agro-processing waste as herbal tea products: optimisation of soluble solids extraction from dust and application to improve sensory profile, colour and flavonoid content of stem infusions.

BACKGROUND: Rooibos represents 10% of the global herbal tea market. Shrinking production areas as a result of climate change necessitate the maximum conversion of plant biomass to product. The present study aimed to determine the potential of rooibos tea processing waste (i.e. fine dust and coarse stems) as potential flavour and herbal tea ingredients, respectively. RESULTS: Hot water extraction of soluble solids (SS) from rooibos dust was optimised and extracts from different production batches (n = 20) were prepared. Their sensory profiles were similar, although less intense than that of infusions of commercial rooibos (n = 20) when diluted to the same SS content. The turbidity and flavonoid content of the diluted extracts was mostly lower (P < 0.05) than that of commercial rooibos. An atypical and negative aroma attribute, 'planky/pencil shavings', was predominant in the stem infusions (n = 20), which contained less SS (P < 0.05) than commercial rooibos. Blends of stem infusion and extract could not effectively mask this negative aroma note (P > 0.05). CONCLUSION: Rooibos dust could be used to produce a rooibos flavour extract, whereas the prominent atypical, negative 'planky/pencil shavings' aroma note of the stems would limit their inclusion in commercial rooibos blends. © 2019 Society of Chemical Industry.

Potential of rooibos, its major C-glucosyl flavonoids, and Z-2-(ß-D-glucopyranosyloxy)-3-phenylpropenoic acid in prevention of metabolic syndrome.

Risk factors of type 2 diabetes mellitus (T2D) and cardiovascular disease (CVD) cluster together and are termed the metabolic syndrome. Key factors driving the metabolic syndrome are inflammation, oxidative stress, insulin resistance (IR), and obesity. IR is defined as the impairment of insulin to achieve its physiological effects, resulting in glucose and lipid metabolic dysfunction in tissues such as muscle, fat, kidney, liver, and pancreatic ß-cells. The potential of rooibos extract and its major C-glucosyl flavonoids, in particular aspalathin, a C-glucoside dihydrochalcone, as well as the phenolic precursor, Z-2-(ß-D-glucopyranosyloxy)-3-phenylpropenoic acid, to prevent the metabolic syndrome, will be highlighted. The mechanisms whereby these phenolic compounds elicit positive effects on inflammation, cellular oxidative stress and transcription factors that regulate the expression of genes involved in glucose and lipid metabolism will be discussed in terms of their potential in ameliorating features of the metabolic syndrome and the development of serious metabolic disease. An overview of the phenolic composition of rooibos and the changes during processing will provide relevant background on this herbal tea, while a discussion of the bioavailability of the major rooibos C-glucosyl flavonoids will give insight into a key aspect of the bioefficacy of rooibos.

Aspalathin from Rooibos (Aspalathus linearis): A Bioactive C-glucosyl Dihydrochalcone with Potential to Target the Metabolic Syndrome.

Aspalathin is a C-glucosyl dihydrochalcone that is abundantly present in Aspalathus linearis. This endemic South African plant, belonging to the Cape Floristic region, is normally used for production of rooibos, a herbal tea. Aspalathin was valued initially only as precursor in the formation of the characteristic red-brown colour of "fermented" rooibos, but the hype about the potential role of natural antioxidants to alleviate oxidative stress, shifted interest in aspalathin to its antioxidant properties and subsequently, its potential role to improve metabolic syndrome, a disease condition interrelated with oxidative stress. The potential use of aspalathin or aspalathin-rich rooibos extracts as a condition-specific nutraceutical is hampered by the limited supply of green rooibos (i.e., "unfermented" plant material) and low levels in "fermented" rooibos, providing incentive for its synthesis. In vitro and in vivo studies relating to the metabolic activity of aspalathin are discussed and cellular mechanisms by which aspalathin improves glucose and lipid metabolism are proposed. Other aspects covered in this review, which are relevant in view of the potential use of aspalathin as an adjunctive therapy, include its poor stability and bioavailability, as well as potential adverse herb-drug interactions, in particular interference with the metabolism of certain commonly prescribed chronic medications for hyperglycaemia and dyslipidaemia.

Myocardial Glucose Clearance by Aspalathin Treatment in Young, Mature, and Obese Insulin-Resistant Rats.

Rooibos, an indigenous South African plant ingested as herbal tea, is well known for its antioxidant effects. This in vitro study investigated aspalathin (C21H24O11), a dihydrochalcone unique to rooibos, for hypoglycemic effects in the context of age- and obesity-induced insulin resistance and the mechanisms involved. Male Wistar rats were allocated into three groups: 16 - 30 weeks feeding with either standard rat chow or a high-caloric diet, or 6 - 10 weeks feeding with standard rat chow. Ventricular cardiomyocytes were isolated by collagenase perfusion digestion, and glucose uptake was determined by 2-[3H]-deoxyglucose accumulation. Viability was tested by trypan blue exclusion or propidium iodide staining. The high-caloric diet significantly increased body weight gain (508.5 ± 50.0 vs. 417.3 ± 40.0 g), visceral adiposity (42.30 ± 10.1 vs. 21.75 ± 7.0 g), and fasting blood glucose (5.7 ± 0.4 vs. 4.7 ± 0.1 mM). Aspalathin (10 µM for 90 min) induced 2-[3H]-deoxyglucose uptake in young cardiomyocytes (37.2 ± 13.9 vs. 25.7 ± 2.5 pmol 2-[3H]-deoxyglucose/mg protein) and enhanced insulin-mediated 2-[3H]-deoxyglucose uptake in control cells (32.4 ± 6.4 vs. 23.5 ± 10.0 pmol 2-[3H]-deoxyglucose/mg protein), but failed to induce 2-[3H]-deoxyglucose uptake in high-caloric diet cells. Aspalathin induced glucose uptake in insulin-sensitive cardiomyocytes from young and aged rats, but not in high-caloric diet animals and enhanced the actions of insulin through a PI3K-dependent mechanism, resulting in an additive response.

Potential Therapeutic Benefits of Green and Fermented Rooibos (Aspalathus linearis) in Dermal Wound Healing.

The process of wound healing constitutes an ordered sequence of events that provides numerous opportunities for therapeutic intervention to improve wound repair. Rooibos, Aspalathus linearis, is a popular ingredient in skin care products, however, little scientific data exists exploring its therapeutic potential. In the present study, we evaluated the effects of fermented and aspalathin-enriched green rooibos in various in vitro models representative of dermal wound healing. Treatment of RAW 264.7 macrophages with fermented rooibos resulted in increased nitric oxide production as well as increased levels of cellular inducible nitric oxide synthase and cyclooxygenase-2, which are typical markers for classically activated macrophages. In contrast, the green extract was devoid of such activity. Using glycated gelatin as a model to mimic diabetic wounds, only the green extract showed potential to reduce cyclooxygenase-2 levels. Considering the role of reactive oxygen species in wound healing, the effects of rooibos on oxidative stress and cell death in human dermal fibroblasts was evaluated. Both fermented and green rooibos decreased cellular reactive oxygen species and attenuated apoptotic/necrotic cell death. Our findings highlight several properties that support the therapeutic potential of rooibos, and demonstrate that green and fermented rooibos present distinctly different properties with regards to their application in wound healing. The proinflammatory nature of fermented rooibos may have therapeutic value for wounds characterised with a delayed initial inflammatory phase, such as early diabetic wounds. The green extract is more suited to wounds burdened with excessive inflammation as it attenuated cyclooxygenase-2 levels and effectively protected fibroblasts against oxidative stress.

A Beneficial Role of Rooibos in Diabetes Mellitus: A Systematic Review and Meta-Analysis.

In a rapid increase in cases of diabetes mellitus worldwide, there has been interested in the use of plant-derived polyphenols as nutraceuticals to prevent the onset and progression of diabetes mellitus and its associated complications. Aspalathus linearis, commonly known as rooibos, is a rich source of uncommon glycosylated plant polyphenols with various critical health-promoting properties, including the prevention and treatment of diabetes mellitus (DM). This study aimed to examine these effects by meta-analyzing the current evidence in diabetic rodent models. Peer-reviewed studies written in English from two databases, PubMed and Embase, were searched up to 28 February 2018. Studies reporting blood glucose levels in diabetic rodents with and without receiving rooibos extracts or their major phenolic compounds are included. Twelve studies enrolling 88 diabetic rodents treated with rooibos extracts or their polyphenols and 85 diabetic control males reported blood glucose levels. The pooled effect size was -0.89 (95% CI: -1.44 to -0.35) with a substantial heterogeneity (I² = 67.0%). This effect was likely to be modified by type of rooibos extracts and their polyphenols and treatment period. Blood glucose levels were significantly lower in diabetic rodent models treated with the phenolic compound rich in rooibos extracts, PPAG.

The Potential of South African Herbal Tisanes, Rooibos and Honeybush in the Management of Type 2 Diabetes Mellitus.

Diabetes mellitus is a metabolic disease that can lead to high morbidity, mortality and long-term complications. Available treatment strategies, which are mainly based on treating hyperglycemia, with insulin and other pharmacological agents are not completely efficient and can even lead to development of unwanted side effects. Scientific evidence suggests that bioactive compounds from teas and other plant-based foods, which are known source of natural antioxidants, could be an attractive strategy to preferentially treat and manage type 2 diabetes mellitus (T2DM) and thus, have significant therapeutic implications. In this review, we attempt an in-depth analysis and discussion of the current progress in our understanding of the antidiabetic potential of two commercialized South Africa herbal tisanes-Rooibos and Honeybush and their polyphenols.

Direct effect of pholyphenol-rich plants, rooibos and ginkgo, on porcine ovarian cell functions.

The polyphenol-rich plants rooibos and ginkgo are widely used in folk medicine and in preparation of foods and drinks, but their effect on reproduction has not been properly studied yet. The aim of our in vitro experiments was to examine the possible direct effect of rooibos and ginkgo on the basic ovarian cell functions-proliferation, apoptosis and release of hormones progesterone (P4) and leptin (L). Porcine ovarian granulosa cells were cultured in the presence of rooibos or ginkgo extract (0, 1, 10 and 100 µg/ml of medium). The accumulation of markers of proliferation (PCNA and cyclin B1) and apoptosis (bax) and their mRNAs was analysed using immunocytochemistry and by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Release of P4 and L was evaluated by radioimmunoassay. It was observed that rooibos or ginkgo addition was able to inhibit proliferation (down-regulates PCNA, cyclin B1 and their mRNAs), to promote apoptosis (accumulation of bax) and to suppress both L and P4 release by ovarian cells. These data suggest a direct inhibitory (anti-proliferative, pro-apoptotic and hormone-suppressing) effect of polyphenol-containing plants rooibos and ginkgo on ovarian functions. The potential anti-reproductive effect of these medical plants is to be taken into account by their consumption.

Evaluation of capillary electrophoresis for the analysis of rooibos and honeybush tea phenolics.

Rooibos and honeybush are popular herbal teas produced from the shrubs of Aspalathus linearis and Cyclopia spp., respectively, which are indigenous to South Africa. Both herbal teas are rich in polyphenols and their consumption is associated with several health benefits, partly ascribed to their phenolic constituents. Quantification of phenolics in extracts and teas for quality control and research purposes is generally performed using HPLC, although dedicated and often species-specific methods are required. CE offers an attractive alternative to HPLC for the analysis of phenolics, with potential benefits in terms of efficiency, speed and operating costs. In this contribution, we report quantitative CZE methods for the analysis of the principal honeybush and rooibos phenolics. Optimal separation for honeybush and rooibos phenolics was achieved in 21 and 32 min, respectively, with good linearity and repeatability. Quantitative data for extracts of "unfermented" and "fermented" rooibos and two honeybush species were statistically comparable with those obtained by HPLC for the majority of compounds. The developed methods demonstrated their utility for the comparison of phenolic contents between different species and as a function of manufacturing processes, thus offering cost effective, although less sensitive and robust, alternatives to HPLC analysis.

Intestinal Transport Characteristics and Metabolism of C-Glucosyl Dihydrochalcone, Aspalathin.

Insight into the mechanisms of intestinal transport and metabolism of aspalathin will provide important information for dose optimisation, in particular for studies using mouse models. Aspalathin transportation across the intestinal barrier (Caco-2 monolayer) tested at 1-150 µM had an apparent rate of permeability (Papp) typical of poorly absorbed compounds (1.73 × 10-6 cm/s). Major glucose transporters, sodium glucose linked transporter 1 (SGLT1) and glucose transporter 2 (GLUT2), and efflux protein (P-glycoprotein, PgP) (1.84 × 10-6 cm/s; efflux ratio: 1.1) were excluded as primary transporters, since the Papp of aspalathin was not affected by the presence of specific inhibitors. The Papp of aspalathin was also not affected by constituents of aspalathin-enriched rooibos extracts, but was affected by high glucose concentration (20.5 mM), which decreased the Papp value to 2.9 × 10-7 cm/s. Aspalathin metabolites (sulphated, glucuronidated and methylated) were found in mouse urine, but not in blood, following an oral dose of 50 mg/kg body weight of the pure compound. Sulphates were the predominant metabolites. These findings suggest that aspalathin is absorbed and metabolised in mice to mostly sulphate conjugates detected in urine. Mechanistically, we showed that aspalathin is not actively transported by the glucose transporters, but presumably passes the monolayer paracellularly.