Structural characterization of Aspalatus linearis polysaccharide and its improving effect on acute alcoholic liver injury

Polysaccharides from natural sources can regulate the composition of intestinal flora through the "gut-liver axis" pathway, potentially ameliorating alcoholic liver injury. Aspalathus linearis, also known as rooibos, is one such natural product that has shown promise in this regard. This study looked at the structural properties of A. linearis polysaccharide (ALP) and how well it would work to treat acute alcoholic liver impairment. This study looks at the composition of monosaccharides, functional groups, and molecular weight (Mw) of a newly discovered water-soluble polysaccharide, named ALP. The polysaccharide is composed of pyranose rings, amide groups, and sulfate groups linked by β-glycosidic linkage. It has a relative Mw of 4.30 × 103 kDa and is composed of glucose, rhamnose, and some other monosaccharides. The study found that treating mice with the model of acute alcoholic liver disease with ALP could alleviate pathological symptoms, inhibit the release of inflammatory cytokines, and suppress indicators of oxidative stress. Experiments have shown that different doses of ALP can activate the P4502E1/Keap1-Nrf2-HO-1 signaling pathway. The regulation of inflammatory factors and downstream antioxidant enzymes occurs as a result. Based on these data, it is likely that ALP protects the liver via the "gut-liver axis" pathway by reducing oxidative stress-related damage, inflammation, and alcohol-related alterations to the gut microbiome. The results indicate that ALP mitigates injury caused by oxidative stress, inflammatory responses, and changes in the gut microbiota induced by alcohol through the "gut-liver axis" pathway, which provides protection to the liver. This provides preliminary evidence for the development of related drugs. PRACTICAL APPLICATION: Researchers extracted a polysaccharide from fresh leaves of Auricularia auricula. The polysaccharide was purified and determined to have a predominantly homogeneous molecular weight. An acute alcoholic liver damage mouse model was established, and it was concluded that the polysaccharide could ameliorate liver injury in mice through the "gut-liver axis" pathway. This novel polysaccharide can be used as an additive to develop functional foods with beneficial effects, which can positively impact the daily maintenance of consumers.

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.

Aspalathin-rich green rooibos tea in combination with glyburide and atorvastatin enhances lipid metabolism in a db/db mouse model

Rooibos (Aspalathus linearis), an indigenous South African plant and its major flavonoid, aspalathin, exhibited positive effects on glycemia and dyslipidemia in animal studies. Limited evidence exists on the effects of rooibos extract taken in combination with oral hypoglycemic and lipid-lowering medications. This study investigated the combined effects of a pharmaceutical grade aspalathin-rich green rooibos extract (GRT) with the sulfonylurea, glyburide, and atorvastatin in a type 2 diabetic (db/db) mouse model. Six-week-old male db/db mice and their nondiabetic lean db+ littermates were divided into 8 experimental groups (n=6/group). Db/db mice were treated orally with glyburide (5 mg/kg bodyweight), atorvastatin (80 mg/kg bodyweight) and GRT (100 mg/kg bodyweight) as mono- and combination therapies respectively, for 5 weeks. An intraperitoneal glucose tolerance test was conducted at 3 weeks of treatment. Serum was collected for lipid analyses and liver tissues for histological examination and gene expression. A significant increase in the fasting plasma glucose (FPG) of the db/db mice compared to their lean counterparts (from 7.98 ± 0.83 to 26.44 ± 1.84, p < 0.0001) was observed. Atorvastatin reduced cholesterol (from 4.00 ± 0.12 to 2.93 ± 0.13, p < 0.05) and triglyceride levels (from 2.77 ± 0.50 to 1.48 ± 0.23, p < 0.05). In db/db mice, the hypotriglyceridemic effect of atorvastatin was enhanced when combined with both GRT and glyburide (from 2.77 ± 0.50 to 1.73 ± 0.35, p = 0.0002). Glyburide reduced the severity and pattern of steatotic lipid droplet accumulation from a mediovesicular type across all lobular areas, whilst combining GRT with glyburide reduced the abundance and severity of lipid droplet accumulation in the centri- and mediolobular areas. The combination of GRT, glyburide and atorvastatin reduced the abundance and severity of lipid accumulation and the intensity score compared to the administered drugs alone. The addition of either GRT or glyburide in combination with atorvastatin had no effect on blood glucose or lipid profiles, but significantly reduced lipid droplet accumulation.

Neuroprotective and anxiolytic potential of green rooibos (Aspalathus linearis) polyphenolic extract

South African rooibos (Aspalathus linearis) tea is globally consumed for its health benefits and caffeine free nature, but no information is available on the neuroprotective capacity of (unfermented) green rooibos. Our aim was to investigate the cytoprotective activity of green rooibos in neuronal cells, including probing antioxidant and enzyme inhibitory properties that could explain observed effects in these cells. We also investigated the anxiolytic potential of green rooibos using zebrafish larval models. Green rooibos extract (Green oxithin™) was assessed for its neuroprotective potential in Neuro-2a cells treated with different concentrations of the extract (12.5-25-50-100 μg mL^-1) and different concentrations of hydrogen peroxide (250 or 125 μM) as oxidizing agent. Cell viability (MTT) and redox status (intracellular ROS) were also quantified in these cells. Antioxidant properties of the extract were quantified using cell-free systems (DPPH, ORAC and xanthine/xanthine oxidase), and potential neuroprotection evaluated in terms of its potential to inhibit key enzymes of the CNS (monoamine oxidase A (MOA-A), acetylcholinesterase (AChE) and tyrosinase (TYR)). Results demonstrated that green rooibos extract exerted significant cytoprotective properties in Neuro-2a cells, particularly when exposed to lethal 250 μM hydrogen peroxide, increasing cell survival by more than 100%. This may be ascribed (at least partially) to its capacity to limit intracellular ROS accumulation in these cells. Data from cell-free systems confirmed that green rooibos was able to scavenge free radicals (synthetic and physiological) in a dose dependent manner with a similar profile activity to vitamins C and E. Green rooibos also acted as a moderate MAO-A inhibitor, but had no significant effect on AChE or TYR. Finally, zebrafish larvae treated with lower doses of green rooibos demonstrated a significant anxiolytic effect in the light-dark anxiety model. Using the PTZ excitotoxicity model, green rooibos was shown to rescue GABA receptor signalling, which together with its demonstrated inhibition of MAO-A, may account for the anxiolytic outcome. Current data confirms that green rooibos could be considered a "functional brain food" and may be a good option as starting ingredient in the development of new nutraceuticals.

Cardioprotective Function of Green Rooibos (Aspalathus linearis) Extract Supplementation in Ex Vivo Ischemic Prediabetic Rat Hearts

Diabetic patients develop ischemic heart disease and strokes more readily. Following an ischemic event, restoration of blood flow increases oxidative stress resulting in myocardial damage, termed ischemia/reperfusion injury. Aspalathus linearis (rooibos), rich in the antioxidant phenolic compound aspalathin, has been implicated as cardioprotective against ischemia/reperfusion injury with undefined mechanism in control rats. Primarily, the therapeutic potential of Afriplex green rooibos extract to prevent ischemia/reperfusion injury in cardiovascular disease-compromised rats was investigated. Additionally, Afriplex Green rooibos extract's cardioprotective signaling on metabolic markers and stress markers was determined using western blotting. Three hundred male Wistar rats received either 16-wk standard diet or high-caloric diet. During the final 6 wk, half received 60 mg/kg/day Afriplex green rooibos extract, containing 12.48% aspalathin. High-caloric diet increased body weight, body fat, fasting serum triglycerides, and homeostatic model assessment of insulin resistance - indicative of prediabetes. High-caloric diet rats had increased heart mass, infarct size, and decreased heart function. Afriplex green rooibos extract treatment for 6 wk lowered pre-ischemic heart rate, reduced infarct size, and improved heart function pre- and post-ischemia, without significantly affecting biometric parameters. Stabilized high-caloric diet hearts had decreased insulin independence via adenosine monophosphate activated kinase and increased inflammation (p38 mitogen-activated protein kinase), whereas Afriplex green rooibos extract treatment decreased insulin dependence (protein kinase B) and conferred anti-inflammatory effect. After 20 min ischemia, high-caloric diet hearts had upregulated ataxia-telangiectasia mutated kinase decreased insulin independence, and downregulated insulin dependence and glycogen synthase kinase 3 β inhibition. In contrast, Afriplex green rooibos extract supplementation downregulated insulin independence and inhibited extracellular signal-regulated kinase 1 and 2. During reperfusion, all protective signaling was decreased in high-caloric diet, while Afriplex green rooibos extract supplementation reduced oxidative stress (c-Jun N-terminal kinases 1 and 2) and inflammation. Taken together, Afriplex green rooibos extract supplementation for 6 wk preconditioned cardiovascular disease-compromised rat hearts against ischemia/reperfusion injury by lowering inflammation, oxidative stress, and heart rate.

Comprehensive in vitro antidiabetic screening of Aspalathus linearis using a target-directed screening platform and cellomics

The antidiabetic potential of Aspalathus linearis has been investigated for over a decade, however, its characterisation remains incomplete with results scattered across numerous journals making the information difficult to compare and integrate. To explore whether any potential antidiabetic mechanisms for A. linearis have been neglected and to compare the suitability of extracts of green and "fermented" A. linearis as potential antidiabetic treatment strategies, this study utilised a comprehensive in vitro antidiabetic target-directed screening platform in combination with high content screening and analysis/cellomics. The antidiabetic screening platform consisted of 20 different screening assays that incorporated 5 well-characterised antidiabetic targets i.e. the intestine, liver, skeletal muscle, adipose tissue/obesity and pancreatic β-cells. Both the green and fermented extracts of A. linearis demonstrated very broad antidiabetic mechanisms as they revealed several promising activities that could be useful in combatting insulin resistance, inflammation, oxidative stress, protein glycation and pancreatic β-cell dysfunction and death - with a strong tendency to attenuate postprandial hyperglycaemia and the subsequent metabolic dysfunction which arises as a result of poor glycaemic control. The green extract was more successful at combatting oxidative stress in INS-1 pancreatic β-cells and enhancing intracellular calcium levels in the absence of glucose. Conversely, the fermented extract demonstrated a greater ability to inhibit α-glucosidase activity as well as palmitic acid-induced free fatty acid accumulation in C3A hepatocytes and differentiated L6 myotubes, however, further studies are required to clarify the potentially toxic and pro-inflammatory nature of the fermented extract.

The Effect of Rooibos (Aspalathus linearis), Honeybush (Cyclopia intermedia) and Sutherlandia (Lessertia frutescens) on Testicular Insulin Signalling in Streptozotocin-Induced Diabetes in Wistar Rats

BACKGROUND

Testicular insulin signalling is altered in diabetic (DM) males. While unravelling the mechanism through which DM exert these detrimental effects, studies have shown the importance of insulin regulation in glucose homeostasis, and how a lack in insulin secretion indirectly led to reduced male fertility. The current study aimed to investigate the role of rooibos, honeybush and Sutherlandia on insulin signalling in the testicular tissue of type I diabetic rats.

METHODS

Animals (n=60) were randomly divided into six groups. The groups include a control group, a vehicle group, and diabetes was induced in the remainder of animals via a single intraperitoneal injection of STZ at 45mg/kg. The remaining four groups included a diabetic control (DC), diabetic + rooibos (DRF), diabetic + honeybush (DHB) and diabetic + Sutherlandia group (DSL). Animals were sacrificed after seven weeks of treatment, and blood and testes were collected.

RESULTS

All diabetic groups (DC, DRF, DHB, DSL) presented with a significant increase in blood glucose levels after diabetes induction compared to the control and vehicle (p<0.001). The DC animals presented with decreased testicular protein expression of IRS-1, PkB/Akt and GLUT4 compared to controls. DRF and DHB animals displayed an acute upregulation in IRS-1, while the DSL group showed improvement in IRS-2 compared to DC. Although, DRF animals presented with a decrease in PkB/Akt, DHB and DSL animals displayed upregulation (22.3%, 48%) compared to controls, respectively.

CONCLUSION

The results taken together, it can be suggested that these infusions may enhance insulin signalling through diverse pathways.

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 catalase enzyme 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 better activity compared to C. sinensis. These teas may thus be used as functional foods in the management of diabetes and other oxidative stress related metabolic disorders.

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

BACKGROUND

More 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.

PURPOSE

In the present study, we investigated whether GRT extract can interfere with the migration and invasion of human CRPC cells.

METHODS

Transwell 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).

RESULTS

Treatment 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.

CONCLUSIONS

GRT treatment suppresses the migration and invasion of CRPC cells via inhibition of YAP signaling and paxillin.

The Potential of South African Herbal Tisanes, Rooibos and Honeybush in the Management of Type 2 Diabetes Mellitus

Diabetes mellitus is a metabolic disease that can lead to high morbidity, mortality and long-term complications. Available treatment strategies, which are mainly based on treating hyperglycemia, with insulin and other pharmacological agents are not completely efficient and can even lead to development of unwanted side effects. Scientific evidence suggests that bioactive compounds from teas and other plant-based foods, which are known source of natural antioxidants, could be an attractive strategy to preferentially treat and manage type 2 diabetes mellitus (T2DM) and thus, have significant therapeutic implications. In this review, we attempt an in-depth analysis and discussion of the current progress in our understanding of the antidiabetic potential of two commercialized South Africa herbal tisanes—Rooibos and Honeybush and their polyphenols.