Effects of rooibos tea extract on antigen-specific antibody production and cytokine generation in vitro and in vivo

Pharmacological activity of Aspalathus linearis extracts: pre-clinical research in view of prospective neuroprotection

OBJECTIVES

Rooibos tea, a very popular everyday beverage made of Aspalathus linearis plant material and containing multiple polyphenolic compounds, reveals an expectation to positively affect various processes observed in the pathogenesis of neurodegenerative diseases as in the case of consumption of other polyphenol-abundant food products.

METHODS

This review is based on available data from pre-clinical in vitro and in vivo studies and presents a broad report on the pharmacological activity of the A. linearis extracts relevant for neurodegenerative diseases.

RESULTS

Flavonoids present in herbal infusions are absorbed from gastro-intestinal tract and may affect the central nervous system. The experimental investigations yield the results indicating to supporting role of A. linearis in the prevention of neurodegeneration, primarily owing to anti-oxidative and anti-inflammatory properties, anti-hyperglycaemic and anti-hyperlipidaemic effects as well as favourable impact on neurotransmission with following cognitive and behavioural after-math.

DISCUSSION

The multiple pharmacological activities and safety of Aspalathus linearis extracts are commented in the manuscript. The continuous rooibos tea consumption seems to be safe (despite anecdotal liver irritation); however, there is a risk of herbal-drug interactions.

The phytotherapeutic potential of commercial South African medicinal plants: current knowledge and future prospects

South Africa, a country considered affluent in nature, ranks third in global biodiversity and encompasses approximately 9% of higher plants on planet Earth. Many indigenous plants have been utilised as herbal medicine, proving successful in treating numerous ailments. From the common cold to pandemic maladies such as COVID-19 in the 21st century and the treatment of incurable diseases, South African inhabitants have found great promise in the healing properties of these plants. Phytomedicine is a rapidly evolving topic, with in-depth bioactive composition analysis, identifying therapeutic action mechanisms, and disease prevention. While we are now poised to take advantage of nature’s medicine cabinet with greater scientific vigour, it remains critical that these practises are done with caution. Overharvesting significantly impacts biodiversity and cultivation practices amidst the beautiful nature of these nutraceuticals. This book chapter focuses on the therapeutic potential of commonly used South African medicinal plants, their ethnopharmacological properties, and how we can conserve this treasure cove we call home for future generations.

Transcriptomics of the Rooibos (Aspalathus linearis) Species Complex

Rooibos (Aspalathus linearis), widely known as a herbal tea, is endemic to the Cape Floristic Region of South Africa (SA). It produces a wide range of phenolic compounds that have been associated with diverse health promoting properties of the plant. The species comprises several growth forms that differ in their morphology and biochemical composition, only one of which is cultivated and used commercially. Here, we established methodologies for non-invasive transcriptome research of wild-growing South African plant species, including (1) harvesting and transport of plant material suitable for RNA sequencing; (2) inexpensive, high-throughput biochemical sample screening; (3) extraction of high-quality RNA from recalcitrant, polysaccharide- and polyphenol rich plant material; and (4) biocomputational analysis of Illumina sequencing data, together with the evaluation of programs for transcriptome assembly (Trinity, IDBA-Trans, SOAPdenovo-Trans, CLC), protein prediction, as well as functional and taxonomic transcript annotation. In the process, we established a biochemically characterized sample pool from 44 distinct rooibos ecotypes (1–5 harvests) and generated four in-depth annotated transcriptomes (each comprising on average ≈86,000 transcripts) from rooibos plants that represent distinct growth forms and differ in their biochemical profiles. These resources will serve future rooibos research and plant breeding endeavours.

Identification of degranulation inhibitors from rooibos (Aspalathus linearis) tea in rat basophilic leukaemia cells

Quercetin, luteolin and chrysoeriol were identified from rooibos tea as degranulation inhibitors in rat basophilic leukaemia cells. The degranulation inhibitory activity of chrysoeriol was first discovered in the present study. When quercetin, luteolin and chrysoeriol were mixed in the ratio that occurs in rooibos tea extract, the mixture inhibited antigen- and calcium ionophore-stimulated degranulation to the same degree as that by the whole rooibos tea extract. These findings indicate that these three flavonoids are the key factors underlying the degranulation inhibitory activity of rooibos tea.

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

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

Free radical scavenging ability of Aspalathus linearis in two in vitro models of diabetes and cancer

The free radical scavenging activity of Aspalathus linearis (Rooibos tea) and its effect on reactive oxygen species (ROS), catalase (CAT), and superoxide dismutase (SOD) were investigated in two in vitro disease models of cancer and diabetes. Although the antioxidant activity of this tea has been reported in several studies, its effects in disease models of ROS-induced oxidative stress have not been systematically evaluated to date. The oxygen radical absorbance capacity (ORAC) assay was used in this study to quantify the antioxidant capacity of the extract, whereas the ROS scavenging ability in hyperglycemia-induced human umbilical vein endothelial cells (HUVECs) and HeLa cells were investigated. The CAT and SOD assays were also carried out in the two disease models in order to evaluate the effect of the extract in the stimulation of these two enzyme activities. The extract was observed to have reduced ROS in a dose-dependent manner in both HUVECs and HeLa cells. The stimulation of the CAT and SOD enzyme activities were observed to be dose-dependent as well. The high ORAC value of the extract indicated the presence of antioxidant compounds which could directly quench ROS, whereby this mechanism of action could be hypothesized to have been further complemented through the stimulation of CAT and SOD. Overall, the Aspalathus linearis extract was observed to have increased the CAT and SOD activities in two in vitro disease models of cancer and hyperglycemia. Given the correlation between the ORAC values, the increases in CAT and SOD activities and the reduction in ROS in a dose-dependent manner, it could be hypothesized that the extract had a significant therapeutic potential for either the prevention of the onset of the two diseases or their progression because ROS has been identified as their root causes.

Amelioration of lipopolysaccharide-induced liver injury by aqueous rooibos (Aspalathus linearis) extract via inhibition of pro-inflammatory cytokines and oxidative stress

BACKGROUND

Acute liver injury occur after intraperitoneal administration of lipopolysaccharide (LPS). Oxidative stress and release of pro-inflammatory cytokines are both implicated in the pathogenesis of LPS-induced acute liver injury. This study investigated the ameliorative effect of fermented rooibos (Aspalathus linearis) extract on LPS-induced acute liver injury.

METHOD

Major phenolic compounds in the fermented rooibos extract by HPLC-DAD, as well as the in vitro antioxidant capacity were quantified before the start of the experiment. Male Wistar rats were randomized into 4 groups (n = 10 per group) and given either water or fermented rooibos extract for 4 weeks before LPS injection. Hepatic function markers, including aminotransferases and lactate dehydrogenase, lipid peroxidation markers, antioxidant enzymes, glutathione redox status, as well as cytokine levels were monitored in the rats.

RESULTS

Injection of LPS significantly increased serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH). Oxidative stress, evidenced by increased thiobarbituric acid reactive substances (TBARS) measured as malondialdehyde (MDA) in plasma and liver, and decreased glutathione redox status (GSH: GSSG ratio) in whole blood and liver was induced in LPS-challenged rats. Furthermore, hepatic levels of pro-inflammatory response markers TNF-α, IL-1β and IL-6 were increased significantly. Pre-feeding the fermented rooibos extract for 4 weeks decreased LPS-induced elevated levels of serum AST and LDH (significantly, p < 0.05) as well as ALT marginally. Consuming rooibos caused an attenuation of the observed increase in plasma and hepatic MDA, decrease in whole blood and liver GSH:GSSG ratio, as well as the changes noted in various antioxidant enzymes. The elevation in TNF-α and IL-6 was significantly suppressed, indicating an inhibition of the induced inflammatory response by rooibos.

CONCLUSION

Overall, our data showed that aqueous rooibos extract attenuated LPS-induced liver injury possibly by modulating oxidative stress and suppressing pro-inflammatory cytokines formation.

Commercially Important Medicinal Plants of South Africa: A Review

There is a growing interest in natural plant-based remedies as a source for commercial products. Around 80% of the South African population use traditional medicines to meet their primary health care needs; however, only a few South African medicinal plants have been exploited to their full potential in terms of commercialization. The opportunity for bioprospecting of plant compounds for novel pharmaceuticals remains largely untapped. Certain renowned medicinal plants of international acclaim including buchu and rooibos are currently contributing to local enterprise; however, other exciting opportunities exist for commonly used plants which have not yet reached the international arena. This paper focuses on the key research and development contributions of 10 commercially important medicinal plants of South Africa. Traditional uses, scientific validation, commercialisation developments, as well as both potential opportunities and setbacks are discussed.

South African herbal teas: Aspalathus linearis, Cyclopia spp. and Athrixia phylicoides--a review

Rooibos (Aspalathus linearis (Brum.f) Dahlg.) and honeybush (Cyclopia Vent. species) are popular indigenous South African herbal teas enjoyed for their taste and aroma. Traditional medicinal uses of rooibos in South Africa include alleviation of infantile colic, allergies, asthma and dermatological problems, while a decoction of honeybush was used as a restorative and as an expectorant in chronic catarrh and pulmonary tuberculosis. Traditional medicinal uses of Athrixia phylicoides DC., or bush tea, another indigenous South African plant with very limited localised use as herbal tea, include treatment of boils, acne, infected wounds and infected throats. Currently rooibos and honeybush are produced for the herbal tea market, while bush tea has potential for commercialisation. A summary of the historical and modern uses, botany, distribution, industry and chemical composition of these herbal teas is presented. A comprehensive discussion of in vitro, ex vivo and in vivo biological properties, required to expand their applications as nutraceutical and cosmeceutical products, is included, with the main emphasis on rooibos. Future research needs include more comprehensive chemical characterisation of extracts, identification of marker compounds for extract standardisation and quality control, bioavailability and identification of bio-markers of dietary exposure, investigation of possible herb-drug interactions and plant improvement with regards to composition and bioactivity.

A review of the bioactivity of South African herbal teas: rooibos (Aspalathus linearis) and honeybush (Cyclopia intermedia)

Rooibos (Aspalathus linearis) and honeybush (Cyclopia intermedia) are popular tisanes in their native South Africa and have a growing worldwide market. Both herbal teas are used traditionally for medicinal purposes and are rich in polyphenols with rooibos a rare source of the dietary dihydrochalcones, aspalathin and nothofagin. The principal polyphenols in honeybush include the xanthone mangiferin and the flavonones hesperitin and isokuranetin. Despite their divergent phytochemical and nutrient compositions, rooibos and honeybush share potent antioxidant and antimutagenic activities in vitro. Animal model studies indicate both herbal teas possess potent antioxidant, immune-modulating and chemopreventive actions. However, human studies of rooibos are limited and of honeybush are absent. No adverse effects of rooibos or honeybush consumption as tisanes have been reported.

Effects of Continuous Ingestion of Herbal Teas on Intestinal CYP3A in the Rat

Tenryocha, rooibos, and guava teas are widely consumed as herbal beverages, especially as a therapy against pollen allergy. To investigate the possible herbal tea-drug interaction the effect of continuous ingestion of these teas on cytochrome P450 (CYP) 3A were studied. Rats (n = 6) were allowed free access to either tea (experimental groups) or water (control) for two weeks. Midazolam (MDZ) (20 mg/kg) was orally administered and the serum concentration was determined. The area under the serum concentration-time curve (AUC(0-infinity)) and the maximum serum concentrations (C(max)) of MDZ were reduced by more than 60% after the treatment of tenryocha and rooibos tea (P<0.05). Intestinal MDZ 1'- and 4-hydroxylation activities mediated by CYP3A were increased in tenryocha and rooibos tea-treated group by 50% compared to the control group, although the results were not statistically significant. Furthermore, the Western blot analysis showed that CYP3A content was significantly increased in the intestine after the treatment of these teas (P<0.05). Hepatic MDZ hydroxylation and CYP3A content were slightly increased by these teas. The results suggested that two weeks ingestion of tenryocha and rooibos tea reduced serum concentration of MDZ by the induction of intestinal CYP3A. The possible interaction between tenryocha or rooibos tea and medicines mediated by CYP3A was suggested.

Activation of murine peritoneal macrophages by water-soluble extracts of Bursaphelenchus xylophilus, a pine wood nematode

In our previous study, water-soluble extracts from Bursaphelenchus xylophilus (B. xylophilus), a pine wood nematode, were shown to enhance interleukin (IL)-4 plus lipopolysaccharide-induced polyclonal immunoglobulin (Ig) E production in vitro in mice and to increase serum levels of an antigen-nonspecific IgE in vivo. Here we examined whether the nematode extracts stimulate immunofunctions of murine peritoneal macrophages. In both resident and inflammatory macrophages, Fcgamma receptor-mediated phagocytosis was markedly activated by B. xylophilus extracts, while non-specific phagocytosis was not. The enhancement of specific phagocytosis was accompanied by an increase in the formation of IgG-Fcgamma receptor rosettes. B. xylophilus extracts also stimulated IL-1beta production in both types of macrophages, and enhanced NO production and mRNA expression of inflammatory cytokines in inflammatory macrophages. These results indicate that the extracts of B. xylophilus contain an activating substance(s) for immunofunctions in macrophages, besides an enhancing factor for polyclonal IgE production.

Mass spectrometric identification and quantification of glycosyl flavonoids, including dihydrochalcones with neutral loss scan mode

We developed a strategy for determination and quantification of glycosyl flavonoids using liquid chromatography-triple quadrupole mass spectrometry with neutral loss scan at 15 and 30eV collision energy in the positive ion mode. The fragmentation patterns of glycosyl flavonoids at 15 and 30eV showed that fragmentation of sugar moiety depended on the type of glycosidic bond to aglycone, the site of C-glycosylation, and the type of aglycone. C-Glycosyl dihydrochalcones especially stood out because they produced [M+H-162](+) even at 15eV such as O-glycoside in spite of C-glycoside. C-Glycosides were classified according to (i) the intensity ratio A of [M+H-150](+) to [M+H-120](+) at 30eV and (ii) the intensity ratio B of [M+H-120](+) at 15eV to one at 30eV. The 8-C-glycosides were A<1 and B<1, the 6-C-glycosides were A>1 and B<1, and the C-glycosyl dihydrochalcones were A>1 and B>>1. Therefore, the intensity ratios of the neutral loss scan of 120 and 150Da at 30eV and those of 120, 162, and 308Da at 15eV allowed sequential distinction among these three types of C-glycosides as well as between O- and C-glycosides. Our method was applied for analysis of Rooibos tea, and the identified glycosides could be quantified specifically by the selected reaction monitoring method.

Effect of Theobroma cacao flavonoids on immune activation of a lymphoid cell line

We analysed the effect of (-)-epicatechin and cocoa extract on the activation of a lymphoid cell line. Particularly the expression of IL-2 receptor alpha (IL-2Ralpha or CD25) and, the secretion of IL-2 and IL-4 were established after flavonoid treatment. Two media culture conditions (1 and 10 % of fetal calf serum supplementation) and the different moments of flavonoid addition (simultaneously or 2 h before cell-activation) were compared. IL-2Ralpha (CD25) expression on activated cells was significantly reduced by epicatechin and cocoa extract in a dose-dependent manner, achieving the highest inhibition of about 50 % when flavonoids were added 2 h before stimulation. IL-2 secretion was also inhibited by the presence of both epicatechin and cocoa extract, displaying 60 and 75 % of inhibition, respectively. Cocoa flavonoids were also able to enhance 3-4.5-fold IL-4 release. In summary, cocoa extract down-modulated T lymphocyte activation and therefore the acquired immune response. This fact could be important in some states of the immune system hyperactivity such as autoimmune or chronic inflammatory diseases.

Ligaria cuneifolia flavonoid fractions modulate cell growth of normal lymphocytes and tumor cells as well as multidrug resistant cells

Flavonoids are ubiquitous compounds present in plant extracts. They represent a major active component of the plant extract and are often known for their anti-inflammatory and anti-tumor effects. Previously, we demonstrated that Ligaria cuneifolia (R et P) Tiegh. (Loranthaceae) extracts inhibit proliferation of murine mitogen-activated lymphocytes as well as murine T leukaemia (LB) and breast tumor cells (MMT). The aim of this study was to assess the anti-proliferative and pro-apoptotic activities of three separate flavonoid fractions derived from L. cuneifolia whole extract (aqueous, methanolic and ethyl acetate) on normal and tumor cells. This was performed as a bio-guided approach leading to the isolation and identification of the active compounds responsible for the effects observed with the whole extract. Results showed that the three fractions differed in the amount and type of compounds found. Only the ethyl acetate flavonoid fraction (100 microg/ml) was able to inhibit significantly the proliferation of Con A stimulated splenocytes or LB and MMT cells. Inhibition of proliferation was mediated by apoptosis as determined by morphology and DNA hypodiploidy. The ethyl acetate fraction modified mRNA expression of IL-2, IL-10 and TGF-beta, while the methanol fraction only modified IL-10 mRNA on LB cells. Our results show that the ethyl acetate flavonoid fraction contains the most active compound/s and is the potential candidate to isolate the active compound/s responsible for the effects observed with L. cuneifolia whole extract.