The Experts below are selected from a list of 375 Experts worldwide ranked by ideXlab platform
Elizabeth Joubert - One of the best experts on this subject based on the ideXlab platform.
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improved hplc method for rooibos phenolics targeting changes due to fermentation
Journal of Food Composition and Analysis, 2017Co-Authors: Nico A Walters, Elizabeth Joubert, André De Villiers, Dalene De BeerAbstract:Abstract The phenolic composition of rooibos ( Aspalathus linearis ) herbal tea is inherently linked to its health-promoting properties. “Fermentation” (oxidation) develops the characteristic flavour and colour of the herbal tea product. Changes to the phenolic composition during fermentation include conversion of aspalathin, a dihydrochalcone unique to rooibos and the major bioactive compound, to eriodictyol-glucopyranoside isomers. These compounds have not been quantified in rooibos plant material to date, due to separation challenges. In this study an improved HPLC method using a core shell column was developed to provide effective separation of a phenolic precursor (enolic Phenylpyruvic Acid-2- O -glucopyranoside, PPAG) and 15 rooibos tea phenolics (aspalathin, four eriodictyol-glucopyranoside isomers and 11 other major phenolic compounds) in a reasonable time. Compounds were tentatively identified using authentic reference standards and/or tandem mass spectrometry. The HPLC method utilising diode-array detection for quantitation was validated. After evaluation of different extraction solvents, a 40% aqueous acetonitrile solution was deemed optimal for extraction of phenolic compounds from rooibos plant material. Green, semi-fermented and fermented plant material from 10 sub-divided rooibos bushes were extracted and analysed. Water extracts, representing food ingredient extracts, were also analysed. The largest decreases with fermentation were observed for the dihydrochalcones, with moderate to small decreases for flavonols. Eriodictyol-glucopyranoside isomer concentrations increased following fermentation.
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Hyperglycemia-induced oxidative stress and heart disease-cardioprotective effects of rooibos flavonoids and Phenylpyruvic Acid-2-O-β-D-glucoside
BMC, 2017Co-Authors: Phiwayinkosi V. Dludla, Elizabeth Joubert, Johan Louw, Christo J. F. Muller, Rabia JohnsonAbstract:Abstract Diabetic patients are at an increased risk of developing heart failure when compared to their non-diabetic counter parts. Accumulative evidence suggests chronic hyperglycemia to be central in the development of myocardial infarction in these patients. At present, there are limited therapies aimed at specifically protecting the diabetic heart at risk from hyperglycemia-induced injury. Oxidative stress, through over production of free radical species, has been hypothesized to alter mitochondrial function and abnormally augment the activity of the NADPH oxidase enzyme system resulting in accelerated myocardial injury within a diabetic state. This has led to a dramatic increase in the exploration of plant-derived materials known to possess antioxidative properties. Several edible plants contain various natural constituents, including polyphenols that may counteract oxidative-induced tissue damage through their modulatory effects of intracellular signaling pathways. Rooibos, an indigenous South African plant, well-known for its use as herbal tea, is increasingly studied for its metabolic benefits. Prospective studies linking diet rich in polyphenols from rooibos to reduced diabetes associated cardiovascular complications have not been extensively assessed. Aspalathin, a flavonoid, and Phenylpyruvic Acid-2-O-β-D-glucoside, a phenolic precursor, are some of the major compounds found in rooibos that can ameliorate hyperglycemia-induced cardiomyocyte damage in vitro. While the latter has demonstrated potential to protect against cell apoptosis, the proposed mechanism of action of aspalathin is linked to its capacity to enhance the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression, an intracellular antioxidant response element. Thus, here we review literature on the potential cardioprotective properties of flavonoids and a phenylpropenoic Acid found in rooibos against diabetes-induced oxidative injury
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major production areas of rooibos aspalathus linearis deliver herbal tea of similar phenolic and phenylpropenoic Acid glucoside content
South African Journal of Botany, 2016Co-Authors: Elizabeth Joubert, B Jolley, I S Koch, Magdalena Muller, M Van Der Rijst, Dalene De BeerAbstract:Abstract A large sample set (n = 209) of fermented, unpasteurised rooibos, spanning the production years 2011–2013, was collected from the two major production areas (Western Cape and Northern Cape, South Africa). Hot water infusions, as prepared for grading, were analysed to quantify the content of ten flavonoid glycosides, the enolic phenylpropenoic Acid glucoside, Phenylpyruvic Acid-2- O -glucoside (PPAG) and the phenolic Acid, ferulic Acid (FA), using a previously validated reversed phase high performance liquid chromatography with diode array detection (RP-HPLC-DAD) method. Principal component analysis showed no clear grouping of samples according to production area and/or production year, based on the content of individual compounds or sub-classes, i.e. dihydrochalcone, flavonol, flavone and PPAG + FA. Discriminant analysis indicated grouping according to year, but not according to production area. ANOVA showed significant production area × year interactions (P O -robinobioside, PPAG and aspalathin. These compounds were present at levels > 9 mg/L, while the other compounds were present at
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modeling of the total antioxidant capacity of rooibos aspalathus linearis tea infusions from chromatographic fingerprints and identification of potential antioxidant markers
Journal of Chromatography A, 2014Co-Authors: Joanna Orzel, Elizabeth Joubert, Dalene De Beer, André De Villiers, M Daszykowski, Malgorzata Kazura, Alexandra E Schulze, Theresa Beelders, Christiaan J Malherbe, B WalczakAbstract: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.
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effects of fermented rooibos aspalathus linearis on adipocyte differentiation
Phytomedicine, 2014Co-Authors: Micheline Sanderson, Elizabeth Joubert, Sithandiwe E. Mazibuko, Dalene De Beer, Rabia Johnson, Carmen Pheiffer, Johan Louw, Christo J. F. MullerAbstract:Rooibos (Aspalathus linearis) contains a rich complement of polyphenols, including flavonoids, considered to be largely responsible for its health promoting effects, including combatting obesity. The purpose of this study was to examine the effect of fermented rooibos hot water soluble solids on in vitro adipocyte differentiation by using differentiating 3T3-L1 adipocytes. Hot water soluble solids were obtained when preparing an infusion of fermented rooibos at "cup-of-tea" strength. The major phenolic compounds (>5 mg/g) were isoorientin, orientin, quercetin-3-O-robinobioside and enolic Phenylpyruvic Acid-2-O-β-D-glucoside. Treatment of 3T3-L1 adipocytes with 10 μg/ml and 100 μg/ml of the rooibos soluble solids inhibited intracellular lipid accumulation by 22% (p<0.01) and 15% (p<0.05), respectively. Inhibition of adipogenesis was accompanied by decreased messenger RNA (mRNA) expression of PPARγ, PPARα, SREBF1 and FASN. Western blot analysis exhibited decreased PPARα, SREBF1 and AMPK protein expression. Impeded glycerol release into the culture medium was observed after rooibos treatment. None of the concentrations of rooibos hot water soluble solids was cytotoxic, in terms of ATP content. Interestingly, the higher concentration of hot water soluble solids increased ATP concentrations which were associated with increased basal glucose uptake. Decreased leptin secretion was observed after rooibos treatment. Our data show that hot water soluble solids from fermented rooibos inhibit adipogenesis and affect adipocyte metabolism, suggesting its potential in preventing obesity.
Ziyin Yang - One of the best experts on this subject based on the ideXlab platform.
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alternative pathway to the formation of trans cinnamic Acid derived from l phenylalanine in tea camellia sinensis plants and other plants
Journal of Agricultural and Food Chemistry, 2020Co-Authors: Lanting Zeng, Xiaoqin Wang, Yinyin Liao, Fang Dong, Haibo Tan, Ming Kang, Ziyin YangAbstract:trans-Cinnamic Acid (CA) is a precursor of many phenylpropanoid compounds, including catechins and aroma compounds, in tea (Camellia sinensis) leaves and is derived from l-phenylalanine (l-Phe) deamination. We have discovered an alternative CA formation pathway from l-Phe via Phenylpyruvic Acid (PPA) and phenyllactic Acid (PAA) in tea leaves through stable isotope-labeled precursor tracing and enzyme reaction evidence. Both PPA reductase genes (CsPPARs) involved in the PPA-to-PAA pathway were isolated from tea leaves and functionally characterized in vitro and in vivo. CsPPAR1 and CsPPAR2 transformed PPA into PAA and were both localized in the leaf cell cytoplasm. Rosa hybrida flowers (economic crop flower), Lycopersicon esculentum Mill. fruits (economic crop fruit), and Arabidopsis thaliana leaves (leaf model plant) also contained this alternative CA formation pathway, suggesting that it occurred in most plants, regardless of different tissues and species. These results improve our understanding of CA biosynthesis in tea plants and other plants.
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increasing postharvest high temperatures lead to increased volatile phenylpropanoids benzenoids accumulation in cut rose rosa hybrida flowers
Postharvest Biology and Technology, 2019Co-Authors: Lanting Zeng, Naoharu Watanabe, Xiaoqin Wang, Fang Dong, Ziyin YangAbstract:Abstract Fragrance is an important quality index of horticultural flowers. Floral volatile formation in flowers during plant growth has been widely studied, but less is known about floral volatile formation in cut flowers and its responses to postharvest conditions. In this study, cut rose (Rosa hybrida cv. Tineke) flowers subjected to 5, 15 and 30 °C for 36 h showed increased concentrations of volatile phenylpropanoids/benzenoids (VPBs) including 2-phenylethanol (2PE), phenylacetaldehyde, benzyl alcohol, benzaldehyde, and phenethyl acetate, but a reduced 3,5-dimethoxytoluene concentration, as temperatures increased. l -[2H8]Phenylalanine (Phe) tracing in vivo suggested that Phenylpyruvic Acid (PPA) was involved in the increase in 2PE in response to increasing temperature. Genes for two aromatic amino Acid aminotransferases (AAATs) were isolated and functionally characterized. Transient expression analyses in Nicotiana benthamiana plants provided in vivo evidence that RhAAAT2 was able to convert l -Phe into PPA, and that it was localized in the cytoplasm. These results advance our understanding of floral aroma formation in flowers after harvest.
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an alternative pathway for the formation of aromatic aroma compounds derived from l phenylalanine via Phenylpyruvic Acid in tea camellia sinensis l o kuntze leaves
Food Chemistry, 2019Co-Authors: Xiaoqin Wang, Lanting Zeng, Yinyin Liao, Ying Zhou, Xinlan Xu, Fang Dong, Ziyin YangAbstract:Abstract Aromatic aroma compounds contribute to flavor of tea (Camellia sinensis (L.) O. Kuntze) and they are mostly derived from l -phenylalanine via trans-cinnamic Acid or directly from l -phenylalanine. The objective of this study was to investigate whether an alternative pathway derived from l -phenylalanine via Phenylpyruvic Acid is involved in formation of aroma compounds in tea. Enzyme reaction with Phenylpyruvic Acid showed that benzaldehyde, benzyl alcohol, and methyl benzoate were derived from Phenylpyruvic Acid in tea leaves. Feeding experiments using [2H8] l -phenylalanine indicated that Phenylpyruvic Acid was derived from l -phenylalanine in a reaction catalyzed by aromatic amino Acid aminotransferases (AAATs). CsAAAT1 showed higher catalytic efficiency towards l -phenylalanine (p ≤ 0.001) while CsAAAT2 showed higher catalytic efficiency towards l -tyrosine (p ≤ 0.001). Both CsAAATs were localized in the cytoplasm of leaf cells. In conclusion, an alternative pathway for the formation of aromatic aroma compounds derived from l -phenylalanine via Phenylpyruvic Acid occurred in tea leaves.
Dalene De Beer - One of the best experts on this subject based on the ideXlab platform.
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improved hplc method for rooibos phenolics targeting changes due to fermentation
Journal of Food Composition and Analysis, 2017Co-Authors: Nico A Walters, Elizabeth Joubert, André De Villiers, Dalene De BeerAbstract:Abstract The phenolic composition of rooibos ( Aspalathus linearis ) herbal tea is inherently linked to its health-promoting properties. “Fermentation” (oxidation) develops the characteristic flavour and colour of the herbal tea product. Changes to the phenolic composition during fermentation include conversion of aspalathin, a dihydrochalcone unique to rooibos and the major bioactive compound, to eriodictyol-glucopyranoside isomers. These compounds have not been quantified in rooibos plant material to date, due to separation challenges. In this study an improved HPLC method using a core shell column was developed to provide effective separation of a phenolic precursor (enolic Phenylpyruvic Acid-2- O -glucopyranoside, PPAG) and 15 rooibos tea phenolics (aspalathin, four eriodictyol-glucopyranoside isomers and 11 other major phenolic compounds) in a reasonable time. Compounds were tentatively identified using authentic reference standards and/or tandem mass spectrometry. The HPLC method utilising diode-array detection for quantitation was validated. After evaluation of different extraction solvents, a 40% aqueous acetonitrile solution was deemed optimal for extraction of phenolic compounds from rooibos plant material. Green, semi-fermented and fermented plant material from 10 sub-divided rooibos bushes were extracted and analysed. Water extracts, representing food ingredient extracts, were also analysed. The largest decreases with fermentation were observed for the dihydrochalcones, with moderate to small decreases for flavonols. Eriodictyol-glucopyranoside isomer concentrations increased following fermentation.
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major production areas of rooibos aspalathus linearis deliver herbal tea of similar phenolic and phenylpropenoic Acid glucoside content
South African Journal of Botany, 2016Co-Authors: Elizabeth Joubert, B Jolley, I S Koch, Magdalena Muller, M Van Der Rijst, Dalene De BeerAbstract:Abstract A large sample set (n = 209) of fermented, unpasteurised rooibos, spanning the production years 2011–2013, was collected from the two major production areas (Western Cape and Northern Cape, South Africa). Hot water infusions, as prepared for grading, were analysed to quantify the content of ten flavonoid glycosides, the enolic phenylpropenoic Acid glucoside, Phenylpyruvic Acid-2- O -glucoside (PPAG) and the phenolic Acid, ferulic Acid (FA), using a previously validated reversed phase high performance liquid chromatography with diode array detection (RP-HPLC-DAD) method. Principal component analysis showed no clear grouping of samples according to production area and/or production year, based on the content of individual compounds or sub-classes, i.e. dihydrochalcone, flavonol, flavone and PPAG + FA. Discriminant analysis indicated grouping according to year, but not according to production area. ANOVA showed significant production area × year interactions (P O -robinobioside, PPAG and aspalathin. These compounds were present at levels > 9 mg/L, while the other compounds were present at
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modeling of the total antioxidant capacity of rooibos aspalathus linearis tea infusions from chromatographic fingerprints and identification of potential antioxidant markers
Journal of Chromatography A, 2014Co-Authors: Joanna Orzel, Elizabeth Joubert, Dalene De Beer, André De Villiers, M Daszykowski, Malgorzata Kazura, Alexandra E Schulze, Theresa Beelders, Christiaan J Malherbe, B WalczakAbstract: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.
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effects of fermented rooibos aspalathus linearis on adipocyte differentiation
Phytomedicine, 2014Co-Authors: Micheline Sanderson, Elizabeth Joubert, Sithandiwe E. Mazibuko, Dalene De Beer, Rabia Johnson, Carmen Pheiffer, Johan Louw, Christo J. F. MullerAbstract:Rooibos (Aspalathus linearis) contains a rich complement of polyphenols, including flavonoids, considered to be largely responsible for its health promoting effects, including combatting obesity. The purpose of this study was to examine the effect of fermented rooibos hot water soluble solids on in vitro adipocyte differentiation by using differentiating 3T3-L1 adipocytes. Hot water soluble solids were obtained when preparing an infusion of fermented rooibos at "cup-of-tea" strength. The major phenolic compounds (>5 mg/g) were isoorientin, orientin, quercetin-3-O-robinobioside and enolic Phenylpyruvic Acid-2-O-β-D-glucoside. Treatment of 3T3-L1 adipocytes with 10 μg/ml and 100 μg/ml of the rooibos soluble solids inhibited intracellular lipid accumulation by 22% (p<0.01) and 15% (p<0.05), respectively. Inhibition of adipogenesis was accompanied by decreased messenger RNA (mRNA) expression of PPARγ, PPARα, SREBF1 and FASN. Western blot analysis exhibited decreased PPARα, SREBF1 and AMPK protein expression. Impeded glycerol release into the culture medium was observed after rooibos treatment. None of the concentrations of rooibos hot water soluble solids was cytotoxic, in terms of ATP content. Interestingly, the higher concentration of hot water soluble solids increased ATP concentrations which were associated with increased basal glucose uptake. Decreased leptin secretion was observed after rooibos treatment. Our data show that hot water soluble solids from fermented rooibos inhibit adipogenesis and affect adipocyte metabolism, suggesting its potential in preventing obesity.
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variation in phenolic content and antioxidant activity of fermented rooibos herbal tea infusions role of production season and quality grade
Journal of Agricultural and Food Chemistry, 2012Co-Authors: Elizabeth Joubert, Dalene De Beer, André De Villiers, Theresa Beelders, Christiaan J Malherbe, Gunnar O SiggeAbstract:Data are required to calculate the dietary exposure to rooibos herbal tea flavonoids and phenolic Acids. Representative content values for the principal phenolic compounds and total antioxidant capacity of fermented rooibos infusion, taking into account variation caused by production seasons (2009, 2010, and 2011) and quality grades (A, B, C, and D), were determined for samples (n = 114) from different geographical areas and producers. The major phenolic constituents were isoorientin and orientin (>10 mg/L), with quercetin-3-O-robinobioside, Phenylpyruvic Acid glucoside, and aspalathin present at >5 mg/L. Isovitexin, vitexin, and hyperoside were present at <3 mg/L. Rutin, ferulic Acid, and isoquercitrin were present at <2 mg/L. Nothofagin was present at <1 mg/L. Only traces of luteolin-7-O-glucoside and the aglycones quercetin, luteolin, and chrysoeriol were present. Substantial variation was observed in the individual content values of the phenolic compounds and total antioxidant capacity within producti...
Christo J. F. Muller - One of the best experts on this subject based on the ideXlab platform.
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Hyperglycemia-induced oxidative stress and heart disease-cardioprotective effects of rooibos flavonoids and Phenylpyruvic Acid-2-O-β-D-glucoside
BMC, 2017Co-Authors: Phiwayinkosi V. Dludla, Elizabeth Joubert, Johan Louw, Christo J. F. Muller, Rabia JohnsonAbstract:Abstract Diabetic patients are at an increased risk of developing heart failure when compared to their non-diabetic counter parts. Accumulative evidence suggests chronic hyperglycemia to be central in the development of myocardial infarction in these patients. At present, there are limited therapies aimed at specifically protecting the diabetic heart at risk from hyperglycemia-induced injury. Oxidative stress, through over production of free radical species, has been hypothesized to alter mitochondrial function and abnormally augment the activity of the NADPH oxidase enzyme system resulting in accelerated myocardial injury within a diabetic state. This has led to a dramatic increase in the exploration of plant-derived materials known to possess antioxidative properties. Several edible plants contain various natural constituents, including polyphenols that may counteract oxidative-induced tissue damage through their modulatory effects of intracellular signaling pathways. Rooibos, an indigenous South African plant, well-known for its use as herbal tea, is increasingly studied for its metabolic benefits. Prospective studies linking diet rich in polyphenols from rooibos to reduced diabetes associated cardiovascular complications have not been extensively assessed. Aspalathin, a flavonoid, and Phenylpyruvic Acid-2-O-β-D-glucoside, a phenolic precursor, are some of the major compounds found in rooibos that can ameliorate hyperglycemia-induced cardiomyocyte damage in vitro. While the latter has demonstrated potential to protect against cell apoptosis, the proposed mechanism of action of aspalathin is linked to its capacity to enhance the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression, an intracellular antioxidant response element. Thus, here we review literature on the potential cardioprotective properties of flavonoids and a phenylpropenoic Acid found in rooibos against diabetes-induced oxidative injury
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effects of fermented rooibos aspalathus linearis on adipocyte differentiation
Phytomedicine, 2014Co-Authors: Micheline Sanderson, Elizabeth Joubert, Sithandiwe E. Mazibuko, Dalene De Beer, Rabia Johnson, Carmen Pheiffer, Johan Louw, Christo J. F. MullerAbstract:Rooibos (Aspalathus linearis) contains a rich complement of polyphenols, including flavonoids, considered to be largely responsible for its health promoting effects, including combatting obesity. The purpose of this study was to examine the effect of fermented rooibos hot water soluble solids on in vitro adipocyte differentiation by using differentiating 3T3-L1 adipocytes. Hot water soluble solids were obtained when preparing an infusion of fermented rooibos at "cup-of-tea" strength. The major phenolic compounds (>5 mg/g) were isoorientin, orientin, quercetin-3-O-robinobioside and enolic Phenylpyruvic Acid-2-O-β-D-glucoside. Treatment of 3T3-L1 adipocytes with 10 μg/ml and 100 μg/ml of the rooibos soluble solids inhibited intracellular lipid accumulation by 22% (p<0.01) and 15% (p<0.05), respectively. Inhibition of adipogenesis was accompanied by decreased messenger RNA (mRNA) expression of PPARγ, PPARα, SREBF1 and FASN. Western blot analysis exhibited decreased PPARα, SREBF1 and AMPK protein expression. Impeded glycerol release into the culture medium was observed after rooibos treatment. None of the concentrations of rooibos hot water soluble solids was cytotoxic, in terms of ATP content. Interestingly, the higher concentration of hot water soluble solids increased ATP concentrations which were associated with increased basal glucose uptake. Decreased leptin secretion was observed after rooibos treatment. Our data show that hot water soluble solids from fermented rooibos inhibit adipogenesis and affect adipocyte metabolism, suggesting its potential in preventing obesity.
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z 2 β d glucopyranosyloxy 3 phenylpropenoic Acid an α hydroxy Acid from rooibos aspalathus linearis with hypoglycemic activity
Molecular Nutrition & Food Research, 2013Co-Authors: Christo J. F. Muller, Elizabeth Joubert, Micheline Sanderson, Carmen Pheiffer, Samira Ghoor, Nireshni Chellan, Stephen J Fey, Johan LouwAbstract:cope The rare enolic Phenylpyruvic Acid-2-O-glucoside, (PPAG:Z-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic Acid), is one of the major constituents of fermented rooibos infusions. 3-Phenylpyruvic Acid (2-oxo-3-phenylpropanoic Acid), without the sugar moiety and with a keto form instead of an enolic arrangement, has been shown to enhance insulin release and glucose uptake in muscle cells. The purpose of this study was to assess if PPAG has similar activity on glucose metabolism. Methods and results Preliminary in vitro studies confirmed that PPAG, isolated from rooibos, enhanced glucose uptake. A dose–response study in Chang cells showed that PPAG enhanced glucose uptake in the concentration range 1.0–31.6 μM (EC50 = 3.6 μM). In obese insulin-resistant rats, oral administration of PPAG lowered fasting glucose concentrations and improved oral glucose tolerance values; messenger RNA expression of glucokinase, glucose transporter 1 and 2, insulin receptor, peroxisome proliferator-activated receptor alpha, and suppressor of cytokine signaling 3, were increased in the liver. This suggests that the liver is mainly responsible for PPAG bioactivity. Conclusion This study describes for the first time that PPAG increases in vitro glucose uptake and improves glucose tolerance in an obese insulin-resistant rat model, suggesting that it has potential as a new class of antidiabetic therapeutics that would contribute to the antidiabetic effect of rooibos.
Johan Louw - One of the best experts on this subject based on the ideXlab platform.
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Hyperglycemia-induced oxidative stress and heart disease-cardioprotective effects of rooibos flavonoids and Phenylpyruvic Acid-2-O-β-D-glucoside
BMC, 2017Co-Authors: Phiwayinkosi V. Dludla, Elizabeth Joubert, Johan Louw, Christo J. F. Muller, Rabia JohnsonAbstract:Abstract Diabetic patients are at an increased risk of developing heart failure when compared to their non-diabetic counter parts. Accumulative evidence suggests chronic hyperglycemia to be central in the development of myocardial infarction in these patients. At present, there are limited therapies aimed at specifically protecting the diabetic heart at risk from hyperglycemia-induced injury. Oxidative stress, through over production of free radical species, has been hypothesized to alter mitochondrial function and abnormally augment the activity of the NADPH oxidase enzyme system resulting in accelerated myocardial injury within a diabetic state. This has led to a dramatic increase in the exploration of plant-derived materials known to possess antioxidative properties. Several edible plants contain various natural constituents, including polyphenols that may counteract oxidative-induced tissue damage through their modulatory effects of intracellular signaling pathways. Rooibos, an indigenous South African plant, well-known for its use as herbal tea, is increasingly studied for its metabolic benefits. Prospective studies linking diet rich in polyphenols from rooibos to reduced diabetes associated cardiovascular complications have not been extensively assessed. Aspalathin, a flavonoid, and Phenylpyruvic Acid-2-O-β-D-glucoside, a phenolic precursor, are some of the major compounds found in rooibos that can ameliorate hyperglycemia-induced cardiomyocyte damage in vitro. While the latter has demonstrated potential to protect against cell apoptosis, the proposed mechanism of action of aspalathin is linked to its capacity to enhance the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression, an intracellular antioxidant response element. Thus, here we review literature on the potential cardioprotective properties of flavonoids and a phenylpropenoic Acid found in rooibos against diabetes-induced oxidative injury
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effects of fermented rooibos aspalathus linearis on adipocyte differentiation
Phytomedicine, 2014Co-Authors: Micheline Sanderson, Elizabeth Joubert, Sithandiwe E. Mazibuko, Dalene De Beer, Rabia Johnson, Carmen Pheiffer, Johan Louw, Christo J. F. MullerAbstract:Rooibos (Aspalathus linearis) contains a rich complement of polyphenols, including flavonoids, considered to be largely responsible for its health promoting effects, including combatting obesity. The purpose of this study was to examine the effect of fermented rooibos hot water soluble solids on in vitro adipocyte differentiation by using differentiating 3T3-L1 adipocytes. Hot water soluble solids were obtained when preparing an infusion of fermented rooibos at "cup-of-tea" strength. The major phenolic compounds (>5 mg/g) were isoorientin, orientin, quercetin-3-O-robinobioside and enolic Phenylpyruvic Acid-2-O-β-D-glucoside. Treatment of 3T3-L1 adipocytes with 10 μg/ml and 100 μg/ml of the rooibos soluble solids inhibited intracellular lipid accumulation by 22% (p<0.01) and 15% (p<0.05), respectively. Inhibition of adipogenesis was accompanied by decreased messenger RNA (mRNA) expression of PPARγ, PPARα, SREBF1 and FASN. Western blot analysis exhibited decreased PPARα, SREBF1 and AMPK protein expression. Impeded glycerol release into the culture medium was observed after rooibos treatment. None of the concentrations of rooibos hot water soluble solids was cytotoxic, in terms of ATP content. Interestingly, the higher concentration of hot water soluble solids increased ATP concentrations which were associated with increased basal glucose uptake. Decreased leptin secretion was observed after rooibos treatment. Our data show that hot water soluble solids from fermented rooibos inhibit adipogenesis and affect adipocyte metabolism, suggesting its potential in preventing obesity.
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z 2 β d glucopyranosyloxy 3 phenylpropenoic Acid an α hydroxy Acid from rooibos aspalathus linearis with hypoglycemic activity
Molecular Nutrition & Food Research, 2013Co-Authors: Christo J. F. Muller, Elizabeth Joubert, Micheline Sanderson, Carmen Pheiffer, Samira Ghoor, Nireshni Chellan, Stephen J Fey, Johan LouwAbstract:cope The rare enolic Phenylpyruvic Acid-2-O-glucoside, (PPAG:Z-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic Acid), is one of the major constituents of fermented rooibos infusions. 3-Phenylpyruvic Acid (2-oxo-3-phenylpropanoic Acid), without the sugar moiety and with a keto form instead of an enolic arrangement, has been shown to enhance insulin release and glucose uptake in muscle cells. The purpose of this study was to assess if PPAG has similar activity on glucose metabolism. Methods and results Preliminary in vitro studies confirmed that PPAG, isolated from rooibos, enhanced glucose uptake. A dose–response study in Chang cells showed that PPAG enhanced glucose uptake in the concentration range 1.0–31.6 μM (EC50 = 3.6 μM). In obese insulin-resistant rats, oral administration of PPAG lowered fasting glucose concentrations and improved oral glucose tolerance values; messenger RNA expression of glucokinase, glucose transporter 1 and 2, insulin receptor, peroxisome proliferator-activated receptor alpha, and suppressor of cytokine signaling 3, were increased in the liver. This suggests that the liver is mainly responsible for PPAG bioactivity. Conclusion This study describes for the first time that PPAG increases in vitro glucose uptake and improves glucose tolerance in an obese insulin-resistant rat model, suggesting that it has potential as a new class of antidiabetic therapeutics that would contribute to the antidiabetic effect of rooibos.