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.

Identifying a urinary peptidomics profile for hypertension in young adults: The African-PREDICT study: Urinary peptidomics and hypertension: Urinary peptidomics and hypertension.

Hypertension is one of the most important and complex risk factors for cardiovascular diseases (CVDs). By using urinary peptidomics analyses, we aimed to identify peptides associated with hypertension, building a framework for future research towards improved prediction and prevention of premature development of CVD. We included 78 hypertensive and 79 normotensive participants from the African-PREDICT study (aged 20-30 years), matched for sex (51% male) and ethnicity (49% black and 51% white). Urinary peptidomics data were acquired using capillary-electrophoresis-time-of-flight-mass-spectrometry. Hypertension-associated peptides were identified and combined into a support vector machine-based multidimensional classifier. When comparing the peptide data between the normotensive and hypertensive groups, 129 peptides were nominally differentially abundant (Wilcoxon p < 0.05). Nonetheless, only three peptides, all derived from collagen alpha-1(III), remained significantly different after rigorous adjustments for multiple comparisons. The 37 most significant peptides (all p ≤ 0.001) served as basis for the development of a classifier, with 20 peptides being combined into a unifying score, resulting in an AUC of 0.85 in the ROC analysis (p < 0.001), with 83% sensitivity at 80% specificity. Our study suggests potential value of urinary peptides in the classification of hypertension, which could enable earlier diagnosis and better understanding of the pathophysiology of hypertension and premature cardiovascular disease development.

Urinary Peptidomics and Pulse Wave Velocity: The African-PREDICT Study.

Increased arterial stiffness is related to early vascular aging and is an independent predictor for cardiovascular disease and mortality. Molecular mechanisms underlying increased arterial stiffness are largely unexplored, especially at the proteome level. We aimed to explore the relationship between pulse wave velocity and urinary proteomics. We included 919 apparently healthy (no chronic illnesses) Black and White men and women (equally distributed) between 20 and 30 years from the African-PREDICT study. Capillary electrophoresis time-of-flight mass spectrometry was used to analyze the urinary proteome. We measured the carotid-femoral pulse wave velocity to estimate arterial stiffness. In the total group, pulse wave velocity correlated positively with collagen-derived peptides including collagen types I, II, III, IV, V, and IX and inversely with collagen type XI (adjusted for mean arterial pressure). Regarding noncollagen-derived peptides, pulse wave velocity positively correlated with polymeric immunoglobulin receptor peptides (n = 2) (all q-value ≤0.05). In multivariable adjusted analyses, pulse wave velocity associated positively and independently with seven urinary peptides (collagen type I, n = 5) (all p-value ≤0.05). We found significant positive and independent associations between pulse wave velocity and the collagen type I-derived peptides, suggesting that dysregulation of collagen type I in the extracellular matrix scaffold could lead to early onset of increased arterial stiffness.

Stability of labile xanthones and dihydrochalcones in a ready-to-drink honeybush beverage during storage.

BACKGROUND: The shelf-life of a functional herbal tea-based beverage is important not only for consumer acceptability, but also for the retention of bioactive compounds. The present study aimed to clarify the role of common iced tea beverage ingredients (citric and ascorbic acids) on the shelf-life stability of an herbal tea-based beverage. A hot water extract of green Cyclopia subternata, also used as honeybush tea, was selected as the main ingredient because it provides different types of phenolic compounds associated with bioactive properties (i.e. xanthones, benzophenones, flavanones, flavones and dihydrochalcones). RESULTS: The model solutions were stored for 180 and 90 days at 25 and 40 °C, respectively. Changes in their volatile profiles and color were also quantified as they contribute to product quality. 3',5'-Di-ß-d-glucopyranosyl-3-hydroxyphloretin (HPDG; dihydrochalcone) and, to a lesser extent, mangiferin (xanthone), were the most labile compounds. Both compounds were thus identified as critical quality indicators to determine shelf-life. The stability-enhancing activity of the acids depended on the compound; ascorbic acid and citric acid enhanced the stability of HPDG and mangiferin, respectively. However, when considering all the major phenolic compounds, the base solution without acids was the most stable. This was also observed for the color and major volatile aroma-active compounds [α-terpineol, (E)-ß-damascenone, 1-p-menthen-9-al and trans-ocimenol]. CONCLUSION: The addition of acids, added for stability and taste in ready-to-drink iced tea beverages, could thus have unwanted consequences in that they could accelerate compositional changes and shorten the shelf-life of polyphenol-rich herbal tea beverages. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Assessment of the stability of compounds belonging to neglected phenolic classes and flavonoid sub-classes using reaction kinetic modeling.

Phenolic compounds are known to degrade and/or undergo changes during food production and storage. Reaction kinetic modeling is generally used to define kinetic parameters of a food system and predict changes during thermal processing and storage. Data for phenolic acids and flavonoids, such as anthocyanins and flavan-3-ols, have been reviewed in detail, but the flavonoid sub-classes, dihydrochalcones and flavanones, have been mostly neglected. Other neglected phenolic classes are xanthones and benzophenones. The stability of these types of compounds is important as they are present in fruits and exposed to heat when processed into juice and jam. Other sources of the compounds are herbal teas, which are also subjected to thermal processing, either during the primary processing of the plant material, or the production of extracts for use as food ingredients. The theoretical background is given to understand the review of literature on these classes/sub-classes. Results of research on kinetic modeling are discussed in detail, while research on compound stability without the application of reaction kinetic modeling is briefly mentioned to provide context. The studies discussed included those focusing on heating during the processing and storage of model solutions, liquid foods, plant material, dried extracts, and extracts formulated with other food ingredients.

Heat treatment improves the sensory properties of the ultrafiltration by-product of honeybush (Cyclopia genistoides) extract.

BACKGROUND: Ultrafiltration of green honeybush (Cyclopia genistoides) extract results in a by-product (retentate). Application of further separation processes for recovery of polyphenols would entail creation of additional waste. Repurposing the retentate as a food flavour ingredient provides an alternative valorization approach. RESULTS: The retentate, suspended in water (270 g L-1 ), was heat-treated at 80 °C for 2, 4, 8 and 16 h, and at 90 °C for 2, 4, 6 and 8 h to change its sensory profile. The heat-treated retentate, diluted to beverage strength (2.15 g L-1 ), had prominent 'grape/Muscat-like' and 'marmalade/citrus' aroma and flavour notes. Overall, heating for ≤ 4 h increased the intensities of positive flavour and aroma notes, while reducing those of 'green/grass', 'hay' and bitterness, whereafter further heating only had a slight effect on the aroma profile at 80 °C (P < 0.05), but not at 90 °C (P ≥ 0.05). The heat treatments, 80 °C/4 h and 90 °C/4 h, were subsequently applied to different batches of retentate (n = 10) to accommodate the effect of natural product variation. Heating at 90 °C produced higher intensities of positive aroma attributes (P < 0.05), but was more detrimental to the phenolic stability, compared to 80 °C. CONCLUSION: After heat treatment, the phenolic content of C. genistoides retentate, reconstituted to beverage strength, still fell within the range of a typical 'fermented' (oxidized) honeybush leaf tea infusion. The change in phenolic composition will not diminish the benefit of an improved sensory profile for the retentate by-product through heating. © 2021 Society of Chemical Industry.

Comprehensive off-line CCC × LC-DAD-MS separation of Cyclopia pubescens Eckl. & Zeyh. phenolic compounds and structural elucidation of isolated compounds.

INTRODUCTION: The minor phenolic constituents of Cyclopia pubescens Eckl. & Zeyh. are unknown and one dimensional (1D) liquid chromatography (LC) is unable to provide sufficient separation. METHODOLOGY: A two-dimensional (2D) LC method incorporating normal-phasehigh performance countercurrent chromatography (NP-HPCCC) in the first dimension (1 D) and reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) as the second dimension (2 D) was developed. The analytical HPCCC method was subsequently scaled up to semi-preparative mode and fractions pooled based on phenolic sub-groups. The phenolic compounds in selected fractions were subsequently isolated using RP-HPLC on a C18 column. Isolated compounds were identified by nuclear magnetic resonance (NMR) spectroscopy. The absolute configurations of compounds were determined by optical rotation and electronic circular dichroism spectra. Sugars were identified by gas chromatography-mass spectrometry (GC-MS) analysis. RESULTS: The comprehensive off-line 2D CCC × LC method gave a good spread of the phenolic compounds. Orthogonality calculated using both the convex hull and conditional entropy methods were 81%. High-resolution mass spectrometric fragmentation spectra obtained from a quadrupole-time-of-flight instrument and ultraviolet-visible (UV-vis) spectral data were used to (tentatively) identify 32 phenolic compounds from the analytical CCC fractions. Of the seven isolated compounds, (2S)-5-O-[α-l-rhamnopyranosyl-(1 → 2)-ß-d-glucopyranosyl]eriodictyol (3) and (2S)-5-O-[α-l-rhamnopyranosyl-(1 → 2)-ß-d-glucopyranosyl]-5,7,3',4'-tetrahydroxyflavan (4) were newly identified in all plants. The other isolated compounds were identified as (2S)-5-O-[α-l-rhamnopyranosyl-(1 → 2)-ß-d-glucopyranosyl]naringenin (1), R-neo-eriocitrin (2), 3-O-α-l-arabinopyranosyl-3,4-dihydroxybenzoic acid (5), 4-O-ß-d-glucopyranosyl-Z-4-hydroxycinnamic acid (6) and 4-(4'-O-ß-d-glucopyranosyl-4'-hydroxy-3'-methoxyphenyl)-2-butanone (7). CONCLUSIONS: Among the 32 compounds (tentatively) identified, only six were previously identified in Cyclopia pubescens using 1D LC. Most of the isolated compounds were also identified for the first time in Cyclopia spp., improving the knowledge of the minor phenolic compounds of this genus.

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.

Left ventricular mass and urinary metabolomics in young black and white adults: The African-PREDICT study.

BACKGROUND AND AIMS: Increased left ventricular mass is an independent predictor for cardiovascular events, and shown to be higher in black than white populations. To gain a better understanding of early factors contributing to increased left ventricular mass in young black adults, we investigated metabolomic profiles, identified and compared metabolites that associated with left ventricular mass index in healthy black and white adults. METHODS AND RESULTS: We included normotensive black and white participants from the African-PREDICT study, with data on urinary metabolomics and echocardiography. Urinary metabolites were measured using three different analytical platforms. Univariate statistical analyses, including independent t-test (adjusted for multiple comparisons), effect size (d ≥ 0.3) and single regression analyses were used to identify metabolites. When comparing the black and white groups, the black group had higher central systolic blood pressure (p > 0.005), whereas left ventricular mass index was similar between the groups (p = 0.97). Three from a total of 192 metabolites were identified to be more abundant (p < 0.046) and inversely associated with left ventricular mass index in the black group only: hydroxyproline (ß = -0.22; p = 0.045), glycine (ß = -0.20; p = 0.049) and trimethylamine (ß = -0.21; p = 0.037). CONCLUSION: Higher urinary levels of hydroxyproline, glycine and trimethylamine were inversely associated with left ventricular mass index in the black adults only. Hydroxyproline and glycine are important in maintaining healthy collagen turnover and stability in the heart. Our results may reflect an increase in collagen biosynthesis and collagen deposition in the left ventricle due to higher central systolic blood pressure in the black population.

Phenolic composition and total antioxidant capacity of South African frozen concentrated orange juice as affected by varietal, seasonal and regional differences.

BACKGROUND: There is epidemiological evidence that fruits and vegetables promote general health due to their phenolic composition. The phenolic composition of three commercially important citrus varieties ('Mandarin', 'Navel' orange and 'Valencia' orange), used for frozen concentrated orange juice (FCOJ) production in South Africa, were evaluated based on variety, production season and geographical region (Western Cape (WC) and Eastern Cape (EC)). RESULTS: FCOJ from the WC had significantly (P < 0.05) lower titratable acidity (TA) and higher total soluble solids (TSS):TA ratio compared to FCOJ produced in the EC. The 'Navel' FCOJ, irrespective of season and region, had the highest (P < 0.05) phenolic content (sum of quantified compounds, TP). Regional effects were clear for the 'Mandarin' variety, the EC 'Mandarin' FCOJ had the highest TP and WC 'Mandarin' had the lowest. Seasonal differences were less evident. Variation that could be ascribed to regional differences were also found for individual phenolic compounds. CONCLUSION: Robust data regarding the phenolic profile of FCOJ produced in South Africa, suitable for inclusion in food composition databases, were collected. © 2018 Society of Chemical Industry.

Impact of steam treatment on shelf-life stability of a xanthone-rich green herbal tea (Cyclopia maculata Andrews Kies) - identifying quality changes during storage.

BACKGROUND: Steam treatment of shredded, fresh C. maculata (honeybush) plant material improves the aroma of this green herbal tea with a slight impact on color and phenolic content, but the effect on storage stability is not known. RESULTS: Steam-treated (60 s before drying) and untreated (control) dried plant material was stored under normal storage conditions in semi-permeable sachets at 25 °C and 60% relative humidity. Reference samples of treated (steamed) and untreated (control) material were stored at 0 °C in impermeable pouches for maximum retention of quality. The stability of the herbal tea was assessed in terms of sensory profile, phenolic composition and color over a storage period of 6 months. Normal storage conditions resulted in a significant (P < 0.05) decrease in green color, especially in steamed samples. Intensities of fruity and sweet-associated aroma attributes increased progressively during storage, while the opposite was observed for vegetal and cereal-like attributes. These changes in the aroma profile were more pronounced in untreated (control) samples. Individual phenolic content remained stable during storage. CONCLUSIONS: Storage of 3 to 6 months may result in a more appealing aroma profile and enhanced product quality, despite loss of green color. © 2018 Society of Chemical Industry.

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.

In Silico Screening of Comprehensive Two-Dimensional Centrifugal Partition Chromatography × Liquid Chromatography for Multiple Compound Isolation.

Isolation of unknown compounds for structural identification and the collection of target molecules to generate unavailable standards remain a challenge when dealing with complex samples. While tedious multistep purification is commonly used, it is not appropriate for a limited amount of sample or when a full recovery of expensive molecules is required. Two-dimensional preparative chromatography in a comprehensive mode provides an effective means to collect a large number of molecules in such a case. However, there is currently a lack of metrics to estimate preparative performances with a minimal number of experiments. An in silico comparative study of various pairs of chromatographic systems is proposed, focusing on the occupation rate and the homogeneity of peak spreading in the 2D separation space. Off-line combination of centrifugal partition chromatography (CPC) with liquid chromatography (LC) exhibits numerous advantages for 2D preparative separation. Our in silico approach was illustrated through the isolation of eight bioactive compounds with very similar structures from Cyclopia genistoides plant by CPC×LC. The column screening was performed considering predictive 2D plots in light of the preparative performance descriptors and compared to real 2D preparative separations.

Bitter Taste Impact and Thermal Conversion of a Naringenin Glycoside from Cyclopia genistoides.

A naringenin derivative, isolated from Cyclopia genistoides, a bitter tasting herbal tea, especially when in green (unoxidized) form, was identified as (2 S)-5-[α-l-rhamnopyranosyl-(1→2)-ß-d-glucopyranosyloxy]naringenin (1). The compound partially epimerizes to (2 R)-5-[α-l-rhamnopyranosyl-(1→2)-ß-d-glucopyranosyloxy]naringenin (2) when heated at different temperatures (80, 90, 100, 110, and 120 °C) for a prolonged period in a phosphate buffer at pH 5. The fractional conversion model predicted the decrease in the concentration of compound 1 the best. The activation energy of the conversion reaction was calculated as 99.16 kJ mol-1. Prolonged heating resulted not only in formation of compound 2 but eventually a decrease in its concentration and the formation of another conversion product, ( E)-2'-[α-l-rhamnopyranosyl-(1→2)-ß-d-glucopyranosyloxy]-4',6',4-trihydroxychalcone (3). In contrast, naringin, glycosylated at C-7, remained stable when heated under the same conditions (100 °C for 6 h at pH 5). The bitter intensity of compound 1 was substantially less than that of naringin, both tested at 0.04 mM, a concentration typical of compound 1 in an herbal tea infusion of green C. genistoides. This comparison indicates that the position of the sugar moiety plays an important role in determining both bitter intensity and heat stability of naringenin glycosides.

Polyphenol-Enriched Fractions of Cyclopia intermedia Selectively Affect Lipogenesis and Lipolysis in 3T3-L1 Adipocytes.

Cyclopia species are increasingly investigated as sources of phenolic compounds with potential as therapeutic agents. Recently, we demonstrated that a crude polyphenol-enriched organic fraction (CPEF) of Cyclopia intermedia, currently forming the bulk of commercial production, decreased lipid content in 3T3-L1 adipocytes and inhibited body weight gain in obese db/db mice. The aim of the present study was to determine whether a more effective product and/or one with higher specificity could be obtained by fractionation of the CPEF by purposely increasing xanthone and benzophenone levels. Fractionation of the CPEF using high performance counter-current chromatography (HPCCC) resulted in four fractions (F1-F4), predominantly containing iriflophenone-3-C-ß-D-glucoside-4-O-ß-D-glucoside (benzophenone: F1), hesperidin (flavanone: F2), mangiferin (xanthone: F3), and neoponcirin (flavone: F4), as quantified by high-performance liquid chromatography with diode array detection (HPLC-DAD), and confirmed by LC-DAD with mass spectrometric (MS) and tandem MS (MSE) detection. All fractions inhibited lipid accumulation in 3T3-L1 pre-adipocytes and decreased lipid content in mature 3T3-L1 adipocytes, although their effects were concentration-dependent. F1-F3 stimulated lipolysis in mature adipocytes. Treatment of mature adipocytes with F1 and F2 increased the messenger RNA expression of hormone sensitive lipase, while treatment with F1 and F4 increased uncoupling protein 3 expression. In conclusion, HPCCC resulted in fractions with different phenolic compounds and varying anti-obesity effects. The activities of fractions were lower than the CPEF; thus, fractionation did not enhance activity within a single fraction worthwhile for exploitation as a nutraceutical product, which illustrates the importance of considering synergistic effects in plant extracts.

Phenolic and physicochemical stability of a functional beverage powder mixture during storage: effect of the microencapsulant inulin and food ingredients.

BACKGROUND: The need for a convenience herbal iced tea product with reduced kilojoules merited investigation of the shelf-life of powder mixtures containing a green Cyclopia subternata Vogel (honeybush) extract with proven blood glucose-lowering activity and alternative sweetener mixture. RESULTS: Prior to long-term storage testing, the wettability of powder mixtures containing food ingredients and the compatibility of their components were confirmed using the static sessile drop method and isothermal microcalorimetry, respectively. The powders packed in semi-sealed containers remained stable during storage at 25 °C/60% relative humidity (RH) for 6 months, except for small losses of specific phenolic compounds, namely mangiferin, isomangiferin, 3-ß-d-glucopyranosyliriflophenone, vicenin-2 and 3',5'-di-ß-d-glucopyranosylphloretin, especially when both citric acid and ascorbic acid were present. These acids drastically increased the degradation of phenolic compounds under accelerated storage conditions (40 °C/75% RH). Accelerated storage also caused changes in the appearance of powders and the colour of the reconstituted beverage solutions. Increased moisture content and aw of the powders, as well as moisture released due to dehydration of citric acid monohydrate, contributed to these changes. CONCLUSION: A low-kilojoule honeybush iced tea powder mixture will retain its functional phenolic compounds and physicochemical properties during shelf-life storage at 25 °C for 6 months. © 2017 Society of Chemical Industry.

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.

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

BACKGROUND: 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 . RESULTS: 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. CONCLUSION: 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.

Assessing similarity analysis of chromatographic fingerprints of Cyclopia subternata extracts as potential screening tool for in vitro glucose utilisation.

Similarity analysis of the phenolic fingerprints of a large number of aqueous extracts of Cyclopia subternata, obtained by high-performance liquid chromatography (HPLC), was evaluated as a potential tool to screen extracts for relative bioactivity. The assessment was based on the (dis)similarity of their fingerprints to that of a reference active extract of C. subternata, proven to enhance glucose uptake in vitro and in vivo. In vitro testing of extracts, selected as being most similar (n = 5; r ≥ 0.962) and most dissimilar (n = 5; r ≤ 0.688) to the reference active extract, showed that no clear pattern in terms of relative glucose uptake efficacy in C2C12 myocytes emerged, irrespective of the dose. Some of the most dissimilar extracts had higher glucose-lowering activity than the reference active extract. Principal component analysis revealed the major compounds responsible for the most variation within the chromatographic fingerprints, as mangiferin, isomangiferin, iriflophenone-3-C-ß-D-glucoside-4-O-ß-D-glucoside, iriflophenone-3-C-ß-D-glucoside, scolymoside, and phloretin-3',5'-di-C-ß-D-glucoside. Quantitative analysis of the selected extracts showed that the most dissimilar extracts contained the highest mangiferin and isomangiferin levels, whilst the most similar extracts had the highest scolymoside content. These compounds demonstrated similar glucose uptake efficacy in C2C12 myocytes. It can be concluded that (dis)similarity of chromatographic fingerprints of extracts of unknown activity to that of a proven bioactive extract does not necessarily translate to lower or higher bioactivity.