Rooibos Extract Research Articles

Effect of the incorporation of a fermented rooibos (Aspalathus linearis) extract in the manufacturing of rabbit meat patties on their physical, chemical, and sensory quality during refrigerated storage

In the present study, rabbit meat patties were formulated with increasing incorporation levels of a fermented rooibos extract (Aspalathus linearis; R): Control (C), R1, R2 and R3 (0, 0.5, 1, 2% w/w R inclusion, respectively). Meat patties were subjected to a 7-day refrigerated storage trial, simulating retail display conditions. At day 0, 1, 3 and 6 of storage, patties drip loss, pH, L*a*b* colour traits (raw patties) and peroxide value (cooked patties) were analysed; at days 0 and 6, total volatile basic nitrogen (raw patties), fatty acid profile and sensory traits (cooked patties) were analysed. Increasing R incorporation levels lowered pH values of rabbit meat patties and increased their redness and yellowness indexes compared to the C group (P < 0.0001). R-treated cooked patties were protected from lipid oxidation compared to C ones (P < 0.0001), and this status was maintained up to the end of the trial. R1 rabbit meat patties showed sensory traits comparable to the C group, whereas R2 and R3 treatments provided negative outcomes. Based on the above-mentioned findings, rooibos can be considered a promising natural additive in the manufacturing of rabbit meat patties, up to the 0.5% incorporation level.

Rooibos (Aspalathus linearis) and honeybush (Cyclopia species) modulate the oxidative stress associated injury of diesel exhaust particles in human umbilical vein endothelial cells

BackgroundPrevious evidence show foods and beverages rich in polyphenolic compounds to have favourable effects on the cardiovascular system. HypothesisThe current study assessed the modulation of oxidative stress and associated inflammation induced by diesel exhaust particles (DEP - SRM 2975) by pre-treatment of human umbilical vein endothelial cells (HUVECs) with aqueous extracts of rooibos [fermented (FR) as well as green form (GR)] and honeybush [fermented form (FH)]. Study designHUVEC are either exposed to DEP (10 µg/ml) for 4 h or pre-treated with 40 and 60 µg/ml of FR or GH or FR, or 50 µg/ml orientin (OR) for 6 h prior to DEP exposure. MethodsIn vitro antioxidant capacity of the extracts was assessed and the polyphenol contents were also assessed by HPLC. ROS, cell viability, lactate dehydrogenase leakage, lipid peroxidation, GSH:GSSG ratios, conjugated diene and protein carbonyl levels were determined as indices of oxidative stress and cytotoxicity. RT-qPCR and western blot were used to assess inflammatory cytokines and antioxidant genes expression. ResultsDEP caused a dose and time-dependent increase in ROS production, significant (p < 0.001) increase in protein carbonyl (PC) formation, thiobarbituric acid reactive substances and conjugated dienes levels (p < 0.01) and a significant reduction in glutathione (GSH) redox status. Pre-incubation with either the herbal extracts or orientin attenuated these effects. The significant increase in IL-1α, IL-6, IL-8, VCAM-1 and ATF4 gene expression caused by DEP (10 µg/ml) were also attenuated by the presence of the FR, GR and FH extracts, and OR . Pre-treatment with the rooibos extracts or flavone orientin enhanced cell viability, reduced LDH leakage, enhanced mRNA expression of NQO1 and Nrf2, but repressed CYP1B1 mRNA induced by DEP. Western blot showed both the herbal tea extracts and orientin to enhance NQO1 and γGSC protein induction by DEP. ConclusionTaken together, the herbal extracts offer protection against DEP-induced oxidative stress and inflammatory response.

The cardiovascular protective effects of rooibos (Aspalathus linearis) extract on diesel exhaust particles induced inflammation and oxidative stress involve NF-κB- and Nrf2-dependent pathways modulation

Studies have shown that diesel exhaust particles (DEP) induced oxidative stress and inflammation. This present study examined the molecular effects of aqueous rooibos extract (RE) on the cardiovascular toxic effect of methanol extract of DEP in exposed Wistar rats. The results showed that DEP caused significant (p < 0.001) increase in MDA and CDs levels in the aorta and heart but this increase was significantly (p < 0.001) attenuated by rooibos extract. DEP induced IL-8, TNFα, IL-1β and decreased IL-10 gene expressions, all of which were reversed in the presence of rooibos extract. The expression of NF-κB, and IκKB genes were also significantly (p < 0.001) induced by DEP in both tissues, but pre-treatment with RE attenuated these effects. In contrast, DEP repressed IκB mRNA level, which was significantly (p < 0.001) reversed by rooibos extract pre-treatment. In addition, pre-treatment with rooibos extract attenuated the increased Nrf2 and HO-1 mRNA levels caused by DEP. This indicates the potential of rooibos extract to protect against DEP-induced cardiovascular toxicity.

Rooibos (Aspalathus linearis) extract, containing eriodictyol-6-C-β-d-glucoside as the active component, stimulates exocrine glands via the M3 muscarinic acetylcholine receptor

Abstract We previously discovered that rooibos extract activates the M3 muscarinic acetylcholine receptor (M3R), a key component of exocrine secretion. In this study, we examined the rooibos extract for active components in vitro and monitored its fast-acting effects against dryness in humans. Our in vitro analysis demonstrated that the M3R-stimulating effect of rooibos extract was similar to that of eriodictyol-6-C-β- d -glucoside (E6CG), whereas other rooibos constituents (aspalathin, orientin, isoorientin or eriodictyol-8-C-β- d -glucoside) were not active. In a placebo-controlled, double-blinded crossover clinical trial, 36 subjects with dryness at the mouth, eyes, and skin consumed a daily dose of either 100 mg rooibos or placebo tablets for three days. Rooibos extract ingestion increased resting-saliva content, tear volume, and stratum corneum moisture content, and reduced the dryness symptoms. In conclusion, rooibos extract contains E6CG as an M3R activator and stimulates exocrine gland secretion, which relieves dryness at the mouth, eyes, and skin in humans.

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.

Inulin as microencapsulating agent improves physicochemical properties of spray-dried aspalathin-rich green rooibos (Aspalathus linearis) extract with α-glucosidase inhibitory activity

Limiting aspalathin degradation during spray-drying of green rooibos extract (GRE) is crucial to produce a functional food ingredient with antidiabetic properties. Retention of aspalathin in a GRE-inulin mixture (1:1, m/m) was not affected by process conditions (inlet air temperature, feed concentration and feed flow rate) tested according to a central composite design. Powder yield could subsequently be optimised by applying response surface methodology and desirability profiling. Inulin delivered a microencapsulated GRE powder with similar physicochemical properties to maltodextrin, commonly used by industry. An advantage of inulin, apart from its low glycaemic load and consequent suitability as functional ingredient, was that it improved wettability of GRE. Inulin had no effect on the intestinal α-glucosidase inhibitory effect of GRE. Aspalathin contributed to the enzyme inhibitory effect of GRE. Approximately 200 µg/mL GRE was required to have the same α-glucosidase inhibitory effect as 42 µg/mL acarbose.

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 17β-hydroxysteroid dehydrogenase 2 (Hsd17β2) was downregulated. In primary hepatocytes, GRE lacked any effect, while aspalathin downregulated Hsd17β2, 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.

The study of antioxidant activity of white tea

Antioxidants protect the organism from the harmful effects of free radicals. High content of antioxidants is characteristic for red wine, olive oil, tea. Today in Russia is well studied the antioxidant activity of black and green tea, but the choice of teas found in the sale, much wider. The aim of the work was to study antioxidant activity of white tea, as well as its comparison with the parameters of green tea and rooibos. Spectrophotometrically compared the antioxidant activity of aqueous extracts white, green tea, drink rooibos using the adrenaline autooxidation reaction in alkaline medium (pH 10.65). The correctness of the spectrophotometric determination was confirmed on the device “Tsvet Yauza-01-AA” (Russia). As a standard used quercetin. In the initial period of time (up to 5 min) tea extracts “Java”, «Elixir immortality» and rooibos are equally affect the values of optical density. After 10 min the optical density takes different values for different extracts, however this time is recommended to determine antioxidant activity. The highest antioxidant activity of the extract has white tea «Greenfield». Rooibos extract antioxidant activity could be compared with “Elixir of immortality” white tea аctivity. The lowest value of antioxidant activity of green tea “Princess JAVA”. The effect of water temperature on the antioxidant activity of extracts was investigated. The highest value was found in tea «Greenfield» at a brewing temperature of 70 °C, which decreases with increasing temperature to 100 °C. The water temperature has a minimal effect on the antioxidant activity of the rooibos extract, but a small maximum at 80 °C is observed. The minimum value of antioxidant activity is the extract of green tea «Princess JAVA», but it increases with the temperature rise up to 100 °C. The study was conducted according to the content of antioxidants from the brewing time. For this, the device “Tsvet Yauza-01-AA” was used. To determine the selected white tea extract «Elixir of Immortality». The temperature was maintained at 100 °C. It is found that the recommended brewing time is two minutes.

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.

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.

Rooibos tea extracts inhibit osteoclast formation and activity through the attenuation of NF-κB activity in RAW264.7 murine macrophages.

Rooibos tea is a naturally sweet and aromatic tea that is native to the Western Cape province of South Africa. Rooibos is usually fermented to produce the traditional reddish brown colour and has been found to have numerous health benefits. These include beneficial effects on osteoblasts; however, its effects on osteoclast formation and activity are unknown. Osteoclasts are large, multinucleated cells responsible for bone resorption. Binding of RANKL to its receptor on osteoclast precursors triggers the NF-κB signalling pathway leading to the formation of osteoclasts. Certain bone destructive diseases, such as osteoporosis, are characterised by overactive osteoclasts. The inhibition of osteoclasts may offer a potential mode to prevent these diseases. The polyphenol contents of both fermented and unfermented tea extracts were similar although the radical scavenging activity of fermented rooibos tea was lower. Both tea extracts were not cytotoxic and inhibited osteoclast formation. Fermented rooibos tea extract caused a greater reduction in osteoclast resorption and the associated gene expression when compared with unfermented rooibos tea. Both tea extracts were shown to attenuate NF-κB activity. Fermented rooibos was found to have a more potent inhibitory effect on osteoclasts than unfermented rooibos extract and therefore may have a beneficial effect on bone health.

Abstract B22: Selective responses of HepG2 cancer cells and primary hepatocytes to growth regulatory effects of Fe (II) and herbal tea flavonoids

Abstract The role of flavonoids as chemopreventive agents is complex due to flavonoid-cell interactions affecting oxidative stress parameters known to play a key role in cell growth and survival. The current study investigated differential anti-proliferative and pro-apoptotic effects and modulation of oxidative status by unfermented (Rg) and polyphenol-enriched (PERg) rooibos (Aspalathus linearis) extracts, while the interaction with Fe (II) in liver cancer (HepG2) cells and primary rat hepatocytes were critically assessed. In contrast to the rooibos extracts, Fe (II) increased cell proliferation in HepG2 cells while in primary hepatocytes both viability and proliferation was decreased. Fe (II) countered the reduction in cell viability and inhibition of proliferation by either Rg or the PERg extracts in HepG2 cells, implying a protective effect. Similar treatments did not significantly alter the growth parameters in primary hepatocytes. Pre-exposure of HepG2 cells to Fe (II) tended to also counteract the reduction in cell viability induced by Rg and PERg while no effect was noticed in primary rat hepatocytes. The PERg extract was more prominent in affecting apoptosis in HepG2 cells, while the opposite was noticed in primary hepatocytes where Rg was more effective. In both cases, Fe (II) counteracted the induction of apoptosis, which was associated with an increase in cell viability. Pre-exposure to iron provide little protective effects, although the induction of apoptosis was markedly reduced, suggesting that a memory effect existed following Fe (II) exposure in both cell culture systems. Thus, Fe (II) decreased the susceptibility of the cells to the effects of the rooibos extracts presumably due to the chelating properties by counteracting the pro-oxidant effects of the rooibos flavonoids. The modulation of cell viability and proliferation by rooibos flavonoids are related to their redox-sensitivity. Both extracts significantly increased glutathione (GSH) levels in HepG2 cells, while only the highest Rg extract concentration resulted in an increase in primary rat hepatocytes. This response is indicative of an antioxidant cellular response presumably by adapting to an oxidative insult effect by the rooibos extracts. Co-exposure with Fe (II) in HepG2 cells counteracted the effects of the rooibos extracts by normalizing the GSH content similar to that of the control level. Pre-exposing cells to Fe (II) showed little memory effect on the reduction of GSH content as the levels was significantly increased above that affected by the rooibos extracts in HepG2 cells suggesting an increased insult on the redox status. In primary hepatocytes a similar effect was noticed although to a far lesser extent. The activity of glutathione peroxidase (GPx) was significantly decreased by the rooibos extracts, while Fe (II) tended to counteract the reduction during the combined and pre-exposure models in both cell culture systems. The reduction in the GPx activity was more prominent in the primary hepatocytes. Understanding the underlying flavonoid/Fe (II) interactions and the modulation of cellular oxidative status and cell growth parameters will provide valuable information to reduce the risk of exposure to polyphenol-enriched neutraceuticals and food supplements in humans. Citation Format: Sedicka Samodien, Maryna de Kock, Sonja Swanevelder, Elizabeth Joubert, Wentzel Gelderblom. Selective responses of HepG2 cancer cells and primary hepatocytes to growth regulatory effects of Fe (II) and herbal tea flavonoids [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr B22.

Abstract B23: The anticancer properties of South African herbal teas utilizing an in vitro pre-exposure anti-inflammatory UVB/keratinocyte model

Abstract The incidence of skin cancer, resulting from exposure to UVB irradiation, has become a global concern as it continues to rise rapidly with the non-melanoma skin cancers, comprised of basal cell carcinoma and squamous cell carcinoma, being the most frequently diagnosed in Caucasian populations. Chronic inflammation is suggested to contribute to cancer development and therefore poses a potential target for chemoprevention. In the skin, keratinocytes and macrophages play an integral part in acute and chronic inflammation, with interleukin 1-α (IL-1α) and tumor necrosis factor α (TNF-α) as key cytokines governing this process. Green tea (Camellia sinensis) and the South African herbal teas, rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.) displayed anti-inflammatory effects in mouse and human skin. To further investigate the anti-inflammatory properties of green tea and the herbal teas, rooibos and honeybush (C. subternata and C. maculata) herbal teas, a pre-exposure UVB-irradiated/keratinocytes cell culture model was developed and validated utilizing human keratinocytes (HaCaT) utilizing the intracellular accumulation of IL-1α as endpoint. Aqueous extracts of the green tea and unfermented herbal teas were prepared, their polyphenolic composition determined by high performance liquid chromatography (HPLC) and their antioxidant activity characterized utilizing different antioxidant assays. Green tea and rooibos exhibited similar antioxidant activities while C. maculata displayed the lowest overall antioxidant activity mainly due to a high mangiferin level, the major polyphenol in honeybush. UVB-induced IL-1α was decreased by pre-exposing the keratinocytes to the green tea extract for 16 hrs prior to UVB-irradiation while a far weaker response was obtained with the rooibos extract. Both the honeybush extracts displayed a significant anti-inflammatory effect in the reduction of IL-1α with C. subternata exhibiting a slightly increased protection at a lower extract concentration. Flavonoid diversity of the teas is likely to explain the differential effects regarding their antioxidant and anti-inflammatory activities. Proposed mechanisms for the anti-inflammatory effects include the modulation of UVB-induced oxidative stress via various pathways and the subsequent down regulation of nuclear factor kappa β (NFκB) and activated protein-1 (AP-1) which are key regulators of cytokine production governing the inflammatory response. Citation Format: Lana Keet, Sylvia Riedel, Amanda C. Swart, E Joubert, WCA Gelderblom. The anticancer properties of South African herbal teas utilizing an in vitro pre-exposure anti-inflammatory UVB/keratinocyte model [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr B23.

Rooibos (Aspalathus linearis) extract enhances boar sperm velocity up to 96 hours of semen storage.

Rooibos (Aspalathus linearis) is a native shrub from South African fynbos and has become very popular in the last decades for its antioxidant and medicinal attributes. Several studies have shown its beneficial properties in numerous cell lines, but to date, the in vitro effects of rooibos extract on sperm cells are still unknown. In this study, boar semen was supplemented with four concentrations both of fermented and unfermented rooibos extracts during 96 h of liquid storage at 17°C. The effects of rooibos extracts on sperm velocity, membrane integrity, and acrosomal status were evaluated at 2 h, 48 h, and 96 h of semen storage. Overall our results indicate that rooibos extract enhances sperm velocity, protects the acrosome structure, and tends to preserve the membrane integrity during semen storage. Although the unfermented rooibos showed higher total polyphenol content and total antioxidant capacity than the fermented one, the latter had better effects on sperm velocity leading to, for instance, an increase of 30% in the rectilinear velocity (VSL) at 48 h compared to the control group. Taking into account the different storage times, we established a suitable range of extracts concentrations to be used in boar semen. The rooibos extract ought to be considered as a powerful and natural source of antioxidants for the preservation of boar semen.

Minimising variation in aspalathin content of aqueous green rooibos extract: optimising extraction and identifying critical material attributes

High levels of aspalathin, an antidiabetic dihydrochalcone, in green rooibos underpins interest in the production of a standardised extract. Elements of a quality-by-design approach were applied to optimise extraction conditions, aiming at the delivery of a dry matter yield (DMY) ≥ 160 g kg-1 and an extract with an aspalathin content (AC) ≥ 80 g kg-1 . Hot water extraction parameters, namely extraction time, extraction temperature and water-to-plant material ratio, were optimised for DMY and aspalathin extraction efficiency (AEE) using Design of Experiments. Good polynomial prediction models were obtained and multiresponse desirability plots indicated 37 min, 93 °C and 23:1 as optimal conditions. Even when using 30 min and 10:1 instead for practical reasons, the target DMY and AC values could be achieved with the caveat that plant material with an AC ≥ 30 g kg-1 is used. Particle size distribution and stem content were identified as contributing to variation in the AC of raw material. By setting raw material specifications in terms of AC, as well as applying practical optimum extraction conditions, 160 g kg-1 extract with an AC ≥ 80 g kg-1 could be consistently achieved from green rooibos plant material. © 2017 Society of Chemical Industry.

P 228 - Green Rooibos Extract improves plasma lipid profile and oxidative status in diabetic non-human primates

Rooibos,a shrub-like leguminous bush endemic to South Africa, is traditionally used as a herbal tea. Unfermented (green) rooibos presents with a much higher polyphenol content, in particular aspalathin which constitutes a major metabolically bioactive compound. Recent studies, both in vitro and ex vivo, highlighted an enhanced glucose uptake effect of aspalathin, associated with increased GLUT 4 translocation to the plasma membrane via AMPK activation. In high fat fed mice, aspalathin also showed a plasma lipid lowering effect. In the present study, we evaluated the effect of 4 weeks of supplementation (90 mg/kg body weight t.i.d) with a pharmaceutical grade aspalathin-enriched green rooibos extract containing ca. 12.8% aspalathin, on gluco-lipidic and oxidative indexes in high fat diet-induceddiabetic and normal non-human primates (Chlorocebus aethiops). Diabetic models were characterized by glucose intolerance and increased total cholesterol and LDL. Moreover, decreased plasma CoQ10 and increased oxidative status were associated with higher levels of oxLDL. Green rooibos supplementation of the diabetic animals significantly improved all listed indices, highlighting the potentialities of this natural extract in modulating some risk factors associated with cardiovascular disease associated with type 2 diabetes.

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

ABSTRACTRisk 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 β-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-(β-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.

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.

Multivariate analysis of variance of designed chromatographic data. A case study involving fermentation of rooibos tea

An ultimate goal of investigations of rooibos plant material subjected to different stages of fermentation is to identify the chemical changes taking place in the phenolic composition, using an untargeted approach and chromatographic fingerprints. Realization of this goal requires, among others, identification of the main components of the plant material involved in chemical reactions during the fermentation process. Quantitative chromatographic data for the compounds for extracts of green, semi-fermented and fermented rooibos form the basis of preliminary study following a targeted approach. The aim is to estimate whether treatment has a significant effect based on all quantified compounds and to identify the compounds, which contribute significantly to it. Analysis of variance is performed using modern multivariate methods such as ANOVA-Simultaneous Component Analysis, ANOVA – Target Projection and regularized MANOVA. This study is the first one in which all three approaches are compared and evaluated. For the data studied, all tree methods reveal the same significance of the fermentation effect on the extract compositions, but they lead to its different interpretation.

Antioxidant-induced reductive stress has untoward consequences on the brain microvasculature.

Antioxidant-induced reductive stress has untoward consequences on the brain microvasculature.