Rooibos Research Articles

A Comparative in Vivo Study on Bambusa Polymorpha, Mentha Piperita and Clitoria Ternatea as Alternative Anxiolytic

This is a continuation of our “Stress Management with Herbal Alternatives” project whereby we are testing traditionally used herbs to scientifically establish their efficacy as anxiolytics for the 1st time. For the current study Bamboo leaf tea, Mint leaf tea and Clitoral bush petal tea were compared for their anxiolytic potency. Male Swiss albino mice were used to test on Open Field test (OFT) and Elevated Plus Maze (EPM) anxiety model. Diazepam (at the dose of 0.25mg/kg body weight) was used as standard and Bangladeshi indigenous bamboo aka Bambusa polymorpha or Bamboo, Mentha piperita or Mint and Clitoria ternatea or Clitoral Bush (at doses of 1g/kg body weight) were the sample. The control group had no intervention. For OFT we tested line crossing, time spent in center, time spent in thigmotaxis and for EPM we measured the number of entry in open and closed hands, time spent in the open and closed hands. Parameters such as rearing, grooming, urination and defecation were also monitored for both tests.The trial results showed Clitoral bush and Mint leaves to have greater anxiolytic activity than Bamboo and Diazepam. Bamboo and Clitoral Bush helped in weight loss, wherelse Diazepam caused weight gain. Based on all criteria, Clitoral bush tea showed highest potential to reduce stress as well as stress related obesity. Results were followed by mint, diazepam and bamboo respectively in their potency for anxiolytic effect.

Phytochemical properties of black tea (Camellia sinensis) and rooibos tea (Aspalathus linearis); and their modulatory effects on key hyperglycaemic processes and oxidative stress.

The comparative phytochemicals, antioxidative and antidiabetic activities of Camellia sinensis (black tea) and Aspalathus linearis (rooibos tea) were studied in vitro and ex vivo. Concentrated infusions of the teas showed significant free radical scavenging activities in vitro. They significantly increased the glutathione level, superoxide dismutase and catalaseenzyme activities in oxidative hepatic injury, while concomitantly depleting malondialdehyde level. The teas significantly inhibited intestinal glucose absorption and α-amylase activities, and elevated muscle glucose uptake. LCMS phytochemical profiling revealed the presence of hydroxycaffeic acid, l-threonate, caffeine, vanillic acid, n-acetylvaline, and spinacetin 3-glucoside in C. sinensis. While quinolinic acid, coumestrol, phloroglucinol, 8-hydroxyquercetagetin, umbelliferone, and ajoene were identified in A. linearis. These results portray the antioxidant and antidiabetic potencies of both teas, with A. linearis showed betteractivitycompared to C. sinensis. These teas may thus be used as functional foods in the management of diabetes and other oxidative stress related metabolic disorders.

Experimental assembly reveals ecological drift as a major driver of root nodule bacterial diversity in a woody legume crop.

Understanding how plant-associated microbial communities assemble and the role they play in plant performance are major goals in microbial ecology. For nitrogen-fixing rhizobia, community assembly is generally driven by host plant selection and soil conditions. Here, we aimed to determine the relative importance of neutral and deterministic processes in the assembly of bacterial communities of root nodules of a legume shrub adapted to extreme nutrient limitation, rooibos (Aspalathus linearis Burm. Dahlgren). We grew rooibos seedlings in soil from cultivated land and wild habitats, and mixtures of these soils, sampled from a wide geographic area, and with a fertilization treatment. Bacterial communities were characterized using next generation sequencing of part of the nodA gene (i.e. common to the core rhizobial symbionts of rooibos), and part of the gyrB gene (i.e. common to all bacterial taxa). Ecological drift alone was a major driver of taxonomic turnover in the bacterial communities of root nodules (62.6% of gyrB communities). In contrast, the assembly of core rhizobial communities (genus Mesorhizobium) was driven by dispersal limitation in concert with drift (81.1% of nodA communities). This agrees with a scenario of rooibos-Mesorhizobium specificity in spatially separated subpopulations, and low host filtering of other bacteria colonizing root nodules in a stochastic manner.

Topic: chemical compositions and mineral content of four selected South African herbal teas and the synergistic response of combined teas

PurposeThe present study was carried out to determine (1) essential minerals, total polyphenols, total flavonoids, moisture and ash of four selected South African herbal teas and (2) the effect of blending bush tea with other known commercial herbal teas.Design/methodology/approachThe method used to determine moisture and ash contents followed that of the Association of Official Analytical Chemists (AOAC). Nine minerals were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). The total phenolic and flavonoid contents were determined by Folin–Ciocalteu assay and aluminum chloride colorimetric assay, respectively.FindingsThe results of the study demonstrated that bush tea had a high ash content of 8.01% and special tea (9.23%), while honeybush (1.96%) and rooibos tea (2.17%) exhibited a low ash percentage. The mineral content was higher in bush tea and special tea than in rooibos tea and honeybush tea except for sodium, which was higher in rooibos tea. The blending of bush tea with special tea improved its potassium content from 22,937.00 mg/kg to 23,379.20 mg/kg. Blending bush tea with rooibos tea at a ratio of 25:75 increased the flavonoid content to 12.21 µg/mL.Research limitations/implicationsThe results of the nutrients composition cannot be generalized as it is influenced by other factors such as soil type and seasons.Social implicationsIncreasing the commercialization of indigenous teas.Originality/valueThe results of the study suggest that bush tea and special tea are nutritionally comparable with South African commercial herbal teas. Thus, the consideration for commercialization of these teas is crucial.

Sensory Characteristics and Volatile Compounds of Herbal Teas and Mixtures of Bush Tea with Other Selected Herbal Teas of South Africa.

South Africa has a traditional heritage of using indigenous herbal teas, and the demand for herbal teas motivated by the functional health benefits has far exceeded global supply. This has led to worldwide interest in the sensory characteristics and volatile compound characterisation of herbal drink formulations. The objective of this study was to investigate the descriptive sensory analysis and volatile compounds of bush, special, honeybush and rooibos tea and the blend of bush tea with special, honeybush and rooibos, respectively. The trained sensory panel scored each tea sample for aroma, taste, aftertaste and mouthfeel attributes using sensory evaluation practices. Compound identification was performed by gas chromatography connected to a mass spectrometer (GC-MS). The results of the study demonstrated that rooibos and honeybush tea had an overall sweet-caramel, honey-sweet, perfume floral and woody aroma while bush tea and special tea depicted green-cut grass, dry green herbal and astringent/dry mouth feel. The GC-MS analyses depicted the following compounds 2-furanmethanol, 2-methoxy-4-vinylphenol, D-limonene, dihydroactinidolide, linalool, (E,E)-2,4-heptadienal, and phytol. The blending of bush tea with rooibos and honeybush tea toned down its astringent mouth feel. Compounds identified in this study may be useful markers for potential herbal tea sensory characteristics.

Development and characterization of collagen-based electrospun scaffolds containing silver sulphadiazine and Aspalathus linearis extract for potential wound healing applications

Bone, skin and soft tissue chronic wounds emanating from burns or bacterial infections which persist due to prolonged tissue inflammation contribute to a delay in wound healing. Electrospun biomimetic scaffolds produced from biodegradable polymers have proven to be a better alternative due to their large surface area to volume ratio and ability to release the drug directly to the wound surface allowing fast and sustained absorbance over the affected wound area. In this study, poly lactic acid (PLA) (20% w/v) and collagen-based (PLA/C) fibrous scaffolds (electrospun at a voltage of 22 kV, flow rate of 0.1 mL/min) containing varying concentrations of silver sulphadiazine (1% w/w, 0.75% w/w) (Ag+S) and Aspalathus linearis (AL) fermented extract (0.025%, 0.1% and 0.5% w/w), were designed and fabricated to increase antimicrobial penetration and cellular biocompatibility. The elastic modulus of samples revealed that incorporating 1% Ag+S and A. linearis extract to PLA solution culminates in a fiber with the superlative stiffness of 2.1.1 GPa. The antimicrobial effect of the scaffolds was evaluated against S. aureus, P. aeruginosa, MRSA and E. coli. PLA/C–Ag+S/AL scaffolds and showed antibacterial activity against both gram +ve and gram −ve bacteria. They were nontoxic to the cells and provided favorable substrates for the neonatal epidermal keratinocytes cells to undergo cell attachment and proliferation. PLA/C–Ag+S/AL scaffolds have a great potential for use in chronic wounds as well as in tissue and bioengineering applications.

Effect of fermented and green Aspalathus linearis extract loaded hydrogel on surgical wound healing in Sprague Dawley rats

Aspalathus linearis (rooibos) has been reported to have a high content of phenolic compounds which elicit antioxidant and anti-inflammatory activity in biological systems. In the present study, we evaluated the effects of “fermented” (oxidised) and green rooibos extracts embedded in gentamicin loaded acrylate copolymer based hydrogels on inflammatory response in surgical wounds in vivo. The major phenolic compounds and a phenolic precursor present in the rooibos extracts were quantified by HPLC. Acute toxicity of the extracts in Swiss albino mice was evaluated up to 1 g/kg body weight. A modification of free radical initial polymerisation of the alkyl acrylate polymer was utilised to formulate hydrogels loaded with different concentrations of the extracts. The hydrogels were evaluated for swelling, skin irritancy, gel index and pH. Surgical wounds were inflicted on 40 healthy male Sprague Dawley rats, randomly designated to groups treated with the extract loaded hydrogels, hydrogel (without extract; control) and 1% framycetin sulphate containing gauze (positive control). In vivo wound healing test post-surgical intervention was carried out following histomorphometric studies. All extract loaded hydrogels shortened the time taken for complete wound closure compared to the control. Hydrogels loaded with fermented rooibos extract performed better than those loaded with green rooibos extract or the positive control by significantly (p < 0.05) shortening the time to complete wound closure from 14 to 10 days. The histologic section of skin showed the absence of inflammatory cell infiltrates within the underlying dermis and subcutaneous fat for all extract loaded hydrogels and no increased dermal stromal fibrosis or other abnormalities in three of the fermented rooibos extract and two unfermented rooibos extract hydrogel formulations compared to the control (p < 0.05). Therapeutic properties of green and fermented rooibos extract loaded hydrogels have been established in vivo, with the best wound healing indices shown by the hydrogels containing fermented rooibos extract. This is possibly a result of a shorter inflammatory phase resulting in quicker wound closure and reduced fibrosis.

Effects of fermented rooibos on sperm from infertile men in vitro

Rooibos (Aspalathus linearis) is indigenous to the Cederberg region in the Western Cape Province of South Africa. It is produced as unfermented and fermented rooibos tea. Previous studies demonstrated improved sperm parameters in male rats owing to its antioxidant properties. This study aims to investigate the effects of fermented rooibos in proven infertile men in vitro.Semen samples were collected after 3–5 days of abstinence from 50 patients attending the infertility clinics of Tygerberg and Vincent Palotti Hospitals, South Africa. After liquefaction, semen was washed with HTF‐BSA (1:5), centrifuged for 10 minutes at 500 ×g and exposed to aqueous extract of fermented rooibos (0, 0.10, 1, 10 and 100 μg/ml) for 1h at 37°C. Thereafter, sperm parameters such as motility, vitality, mitochondrial membrane potential, ROS production, capacitation and acrosome reaction were analyzed.Our results showed no effect of the aqueous extracts at any concentration used on the respective sperm parameters. In conclusion, fermented rooibos has no direct effect on the human sperm in vitro. Hence, the positive effect observed in previous studies may rather be due to the systemic antioxidant effect on the male reproductive system in vivo.Support or Funding InformationThuthuka fundinding instrument, National Research Foundation, South Africa (TTK170426228930)

Stress tolerant traits and root proliferation of Aspalathus linearis (Burm.f.) R. Dahlgren grown under differing moisture regimes and exposed to drought

In recent decades climate change has impacted ecosystems negatively globally with Mediterranean systems being particularly vulnerable. Changes in rainfall pattern and amounts have led to increases in flooding and droughts in certain areas of the world. Many important agricultural crops such as Aspalathus linearis (Burm.f.) R. Dahlgren, rooibos tea, rely on the Mediterranean-type seasonality in the Western Cape, South Africa. Aspalathus linearis plants, which occur naturally in the Cedarberg, grow in hot and dry summer conditions and have a root that penetrates the soil down to 2 m, yet no work has looked at the root response to drought under low rainfall environments. The objective of this study was to determine the physiological and morphological response of A. linearis plants grown at two different water regimes to drought. A potted glasshouse experiment was carried out where drought stress (withdrawing watering) was imposed on well-watered and low moisture supplied plants. The low moisture droughted plants exhibited drought tolerant mechanisms which included higher root/shoot ratios as well as thinner roots, both of which are effective for water and nutrient uptake. Overall, plants in the 30% FC treatment recorded lower Pmax, gs and E after three days in the drought conditions while 70% FC plants were only affected after five days. Furthermore, plants grown under low moisture conditions produced 50% lower biomass compared to plants grown under adequate moisture conditions. This implies that low rainfall and the occurrences of dry spells and drought, associated with climate change are likely to reduce the production of A. linearis in the Cederberg area.

Aspalathin-rich green Aspalathus linearis extract suppresses migration and invasion of human castration-resistant prostate cancer cells via inhibition of YAP signaling

BackgroundMore than 80% of advanced prostate cancer (PCa) cases have bone metastasis, with a 5-year survival rate of 25%. Previously, we reported that GRT, a standardized, pharmaceutical-grade aspalathin-rich extract (12.78 g aspalathin/100 g extract), prepared from green rooibos produced from the leaves and fine stems of Aspalathus linearis, inhibits the proliferation of PCa cells, meriting this investigation to determine if GRT can suppress the migration and invasion of castration-resistant prostate cancer (CRPC) cells. PurposeIn the present study, we investigated whether GRT extract can interfere with the migration and invasion of human CRPC cells. MethodsTranswell assays were used to explore the effects of GRT on the migration and invasion of CRPC cells. Micro-Western Array (MWA) and Western blot analysis were carried out to unravel the underlying molecular mechanism(s). ResultsTreatment with 25–100 μg/ml GRT suppressed the migration and invasion of LNCaP C4-2B and 22Rv1 CRPC cells. MWA and Western blot analysis indicated that GRT treatment suppressed the protein level of yes-associated protein (YAP), macrophage stimulating 1 protein (MST1), phospho-MST1/phospho-MST2 T183/T180, and paxillin, but increased the abundance of E-cadherin. Over-expression of YAP rescued the suppressive effects of GRT on migration and invasion of CRPC cells. Treatment with the major flavonoid of GRT — the C-glucosyl dihydrochalcone, aspalathin — at a concentration of 75–100 μg/ml also reduced the migration and invasion of CRPC cells, and the inhibition was partially rescued by YAP over-expression. ConclusionsGRT treatment suppresses the migration and invasion of CRPC cells via inhibition of YAP signaling and paxillin.

Establishment of Simple Cell-based Screening Assay and the Identification of Potent Antiviral Activity of a Plant Extract against HSV-1

Backgrounds: Drug screening is a time-consuming and costly process confronted with low productivity and challenges in using animals, which limits the discovery of new drugs. The cellbased assay allows the minimization of using the animal models and can provide more relevant in vivo biological information than biochemical assay. Objective: We aimed to establish a simple cell-based screening assay for the discovery of lead extract against HSV-1. Materials and Methods: Assay setting up was performed by optimization of the cell, incubation time, virus titer, and determination of Z value. Results: We have successfully established reproducible methods, by setting up assay plate including determination: 1) Vero cells as a model for HSV-1 infection, 2) Incubation for 5 days as sufficient time for CPE endpoint at monolayer cells, 3) 100 TCID50/well HSV-1 as infection titer which caused high percentage of cell detachment, 4) determination of Z value of 100 TCID50/well infection > 0.5. In addition, the established system was tested using ACV as the most common anti-HSV drug. Furthermore, we demonstrated the current system to screen extracts from Acacia nilotica, Uncaria gambir and Aspalathus linearis against HSV-1. It was observed that the alkaline extract of Uncaria gambir exhibited the highest SI (12.5) compared to other extracts. Conclusion: We demonstrated current cellbased screening system was reproducible and able to identify lead extracts against HSV-1 infection.

Emergence of β-rhizobia as new root nodulating bacteria in legumes and current status of the legume–rhizobium host specificity dogma

Recent developments in the legume rhizobium symbiotic interaction particularly those related to the emergence of novel strains of bacteria that nodulate and fix nitrogen in legumes is gaining momentum. These novel strains of bacteria were mostly isolated from the root nodules of indigenous and invasive legumes belonging to the sub families Papilionoideae and Mimosoideae in South Africa, South America and South East China. These rhizobia are phylogenetically and taxonomically different from the traditional 'alpha rhizobia' and are termed 'β-rhizobia' as they belong to the β-sub class of Proteobacteria. There are also new reports of novel species of root nodulating bacteria from the α-Proteobacteria, not known for several decades since the discovery of rhizobia. However, in this review focus is given to the emerging β-rhizobia isolated from the indigenous Papilionoid legumes in the Cape Floristic regions in South Africa and the indigenous and invasive Mimosoid legumes in South America and South East Asia respectively. The nodulation of the indigenous South African Papilionoid legumes including that of Aspalathus linearis (rooibos) is discussed in a bit detail. Previous reports indicated that A. linearis is very specific in its rhizobium requirement and was reported to be nodulated by the slow growing Bradyrhizobium spp. This review however summarizes that the bacteria associated with the root nodules of A. linearis belong to members of both the alpha (α) Proteobacteria that include Mesorhizobium, Rhizobium and Bradyrhizobium spp. and the beta (β) Proteobacteria represented by the genus Burkholderia (now reclassified as Paraburkholderia). In addition, the occurrence of Paraburkholderia as the newly emerging root nodule symbionts of various other legumes has been discussed. In doing so, the review highlights that nodulation is no longer restricted to the traditional 'rhizobia' group following the emergence of the new beta rhizobia as potential nodulators of various indigenous legumes. It thus provides some insights on the status of the legume-rhizobium host specificity concept and the loss of this specificity in several symbiotic associations that puts the long held dogma of host specificity of the legume rhizobium symbiosis in a dilemma.

Rooibos (Aspalathus linearis) Genome Size Estimation Using Flow Cytometry and K-Mer Analyses.

Plant genomes provide information on biosynthetic pathways involved in the production of industrially relevant compounds. Genome size estimates are essential for the initiation of genome projects. The genome size of rooibos (Aspalathus linearis species complex) was estimated using DAPI flow cytometry and k-mer analyses. For flow cytometry, a suitable nuclei isolation buffer, plant tissue and a transport medium for rooibos ecotype samples collected from distant locations were identified. When using radicles from commercial rooibos seedlings, Woody Plant Buffer and Vicia faba as an internal standard, the flow cytometry-estimated genome size of rooibos was 1.24 ± 0.01 Gbp. The estimates for eight wild rooibos growth types did not deviate significantly from this value. K-mer analysis was performed using Illumina paired-end sequencing data from one commercial rooibos genotype. For biocomputational estimation of the genome size, four k-mer analysis methods were investigated: A standard formula and three popular programs (BBNorm, GenomeScope, and FindGSE). GenomeScope estimates were strongly affected by parameter settings, specifically CovMax. When using the complete k-mer frequency histogram (up to 9 × 105), the programs did not deviate significantly, estimating an average rooibos genome size of 1.03 ± 0.04 Gbp. Differences between the flow cytometry and biocomputational estimates are discussed.

Ives, Sarah. Steeped in heritage: the racial politics of South African rooibos tea. xv, 255 pp., map, illus., bibliogr. Durham, N.C.: Duke Univ. Press, 2017. £20.99 (paper)

Ives, Sarah. Steeped in heritage: the racial politics of South African rooibos tea. xv, 255 pp., map, illus., bibliogr. Durham, N.C.: Duke Univ. Press, 2017. £20.99 (paper)

Aspalathin Protects Insulin-Producing β Cells against Glucotoxicity and Oxidative Stress-Induced Cell Death.

Aspalathin, the main polyphenolic phytochemical of rooibos (Aspalathus linearis), has been attributed with health promoting properties, including a glucose lowering effect that can prove interesting for application as nutraceutical or therapeutic in (pre-)diabetics. Preservation of β cell mass in the pancreas is considered a key issue for diabetes prevention or treatment, therefore the aim is to investigate whether aspalathin also has β cell cytoprotective potential. Rat pancreatic islets and the β cell line Insulinoma 1E (INS1E) are studied in vitro after exposure to various cytotoxic agents, namely streptozotocin (STZ), hydrogen peroxide, or chronic high glucose. The effect of aspalathin on cell survival and apoptosis is studied. Expression of relevant cytoprotective genes is analyzed by qRT-PCR and proteins by Western blot. Aspalathin is found to protect β cells against cytotoxicity and apoptosis. This is associated with increased translocation of nuclear factor erythroid 2-related factor 2 (NRF2) and expression of its antioxidant target genes heme oxygenase 1 (Hmox1), NAD(P)H quinone dehydrogenase 1 (Nqo-1), and superoxide dismutase 1 (Sod1). It is proposed that aspalathin protects β cells against glucotoxicity and oxidative stress by increasing the expression of NRF2-regulated antioxidant enzymes. This indicates that aspalathin is an interesting β cell cytoprotectant.

A new analytical concept based on chemistry and toxicology for herbal extracts analysis: From phenolic composition to bioactivity

Studies regarding the bioactivity of teas are mainly based on the phenolic composition and in vitro antioxidant activity of the herbal species used in their preparation. The aim of this study was to compare the in vitro and ex vivo antioxidant activity, cytotoxic/antiproliferative activity against cancer cells, the inhibitory activity of α-amylase, α-glucosidase and angiotensin I-converting enzymes, as well as the inhibition of DNA-induced fission of the peroxyl radical, in relation to aqueous extracts of Camellia sinensis var. sinensis (CS), Ilex paraguariensis (IP), Aspalathus linearis (AL) and an optimised extract (OT) containing the three herb species. A bivariate and multivariate statistical approach was employed to associate functional activities with individual phenolic composition. The CS and OT extracts showed the highest levels of hesperidin, quercetin-3-rutinoside, (-)-epigallocatechin-3-gallate and isoquercitrin. The CS and OT extracts showed the highest antioxidant activity, greater ability to inhibit α-amylase and proliferation of HCT8 cells, and greater ability to reduce Folin-Ciocalteu reagent. The AL extract, which is the major source of quercetin-3-rutinoside, hesperidin and isoquercitrin, showed the highest ability to inhibit α-glucosidase, the inhibition of LDL oxidation and protection of human erythrocytes. The IP extract showed the highest inhibition of lipoperoxidation in brain homogenate of Wistar rats, antihypertensive activity, and A549 cell proliferation; chlorogenic acid was its major phenolic compound. In general, the in vitro functionality of each extract was dependent on its chemical composition and the OT extract presented the most varied phenolic composition, and biological activity similar to the CS sample. In conclusion, the mixture of CS, AL, and IP represents a chemical and functional-based strategy to develop functional teas.

Oxidative Fragmentation of Aspalathin Leads to the Formation of Dihydrocaffeic Acid and the Related Lysine Amide Adduct.

In the present study, the degradation of C-glucosidic dihydrochalcone aspalathin as the major phenolic compound in rooibos (Aspalathus linearis) was investigated. Analyses by gas chromatography-mass spectrometry of aqueous aspalathin-lysine incubations after silylation showed the formation of dihydrocaffeic acid [3-(3,4-dihydroxyphenyl)-propionic acid] under oxidative conditions as a novel degradation product up to 10 mol %. High-performance liquid chromatography analyses revealed the concurrent formation of the dihydrocaffeic acid lysine amide at about 30-fold lower concentrations, which was unequivocally verified by synthesis of an authentic reference standard. The amide was also verified in aspalathin-protein incubations after enzymatic hydrolysis by high-performance liquid chromatography-tandem mass spectrometry analyses. Thus, the covalent interaction of phenolic plant compounds with proteins under mild conditions (ambient temperatures and neutral pH) was confirmed for the first time. Acid and free amide were also quantitated in rooibos teas with significantly higher values in fermented varieties. The mechanism of formation was clarified to be initiated by singlet oxygen and to include a rearrangement-fragmentation mechanism with 1,2,3,5-tetrahydroxybenzene as the counterpart.

Chemical Underpinning of the Tea Bag Index: An Examination of the Decomposition of Tea Leaves

Decomposition is a key flux of terrestrial carbon to the atmosphere. Therefore, gaining a better understanding of how plant litter decomposes in soil, and what governs this process, is vital for global climate models. The Tea Bag Index (TBI) was introduced by Keuskamp et al. (2013) as a novel method for measuring litter decomposition rate and stabilisation. The TBI uses two types of tea bags representing fast (green tea) and slow (rooibos tea) decomposition substrates as standardised litter bags. To date, the TBI method has been used in over 2000 locations across the globe. However, before now, there has been no information on how the composition of the tea leaves change during incubation. These data are crucial in determining the validity of the use of the TBI method globally, to ensure the tea leaves decompose in a way that is representative of so-called “native” litters. To provide chemical underpinning of the TBI method, a laboratory incubation of the tea bags was conducted with destructive sampling at 0, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, and 91 d. The incubated tea was analysed for total C and N. In addition, C was characterised as alkyl, O-alkyl, aromatic, or carbonyl C using solid-state 13C nuclear magnetic resonance spectroscopy with cross-polarization and magic angle spinning (CPMAS NMR). The results suggest that changes in carbon in both tea types are comparable to other litter studies, with a net decrease in total C and relative proportion of O-alkyl C fraction, which contains carbohydrates and cellulose. We conclude that the decomposition of tea leaves in the bags used in the TBI is representative of other litters.

Rooibos Tea and Health: A Systematic Review of the Evidence from the Last Two Decades

An expanse of research has investigated the effects of black and green teas in relation to aspects of health. Rooibos tea, also known as Red bush is derived from the South African Cape fynbos plant, Aspalathus linearis, and is caffeine free, naturally sweet and abundant in polyphenols. Evidence related to the health aspects of drinking Rooibos tea is advancing, but does not appear to have been collated. Therefore, we aimed to examine the health effects of Rooibos tea through a systematic review of the literature. A PUBMED search was undertaken (2000 up to June 2020) for human and laboratory studies investigating the efficacy of Rooibos in relation to health. Seven human studies and 49 laboratory studies were identified. Overall Rooibos tea consumption seems to benefit the lipid and redox profiles of those at risk of cardiovascular disease. It also appears to possess other promising ‘general’ effects on glycaemic control, bone, liver, cognitive and respiratory health. Ongoing research using standardised interventions is now needed to help formulate congruent conclusions that are relevant to public health.

Effect of vermicompost tea on rooibos (Aspalathus linearis) growth and rhizosphere microbial diversity under field conditions

Increasing demand for rooibos tea (Aspalathus linearis) requires producers to increase production in a sustainable manner. The aim of the study was to examine the effect of applying vermicompost tea (VCT) (100 and 500 L ha–1 month–1) and tap water drenches on one-year old rooibos nutrient uptake, and tea yields and rhizosphere microbial diversity under field conditions in the Nieuwoudtville region. The application of VCT solutions had no significant effect on rooibos survival or tea yields compared to the same volume of tap water. The application of tap water with or without VCT resulted in significant increases in plant survival (23–31% higher), resulting in lower tea yields (38–66% lower) likely due to increased plant competition. The application of VCT drench applied at 5 times the supplier’s recommendations (500 L ha–1 month–1) significantly enhanced foliar P and Fe and reduced foliar Al, attributed to the organic acids in VCT. VCT application at 100 L ha–1 significantly enhanced bacterial species diversity and decreased dominance. Further research is needed to identify which bacterial species are increasing with addition of vermicompost tea. Application of compost tea with higher mineral N content would likely be more beneficial for enhancing yields.