Aspalathin, a C-glucosyl Dihydrochalcone From Rooibos Improves the Hypoglycemic Potential of Metformin in Type 2 Diabetic (db/db) Mice

Translation of preclinical ethnomedicine data in LMICs: the example of rooibos

All disease, but especially non-communicable diseases, are related to dysfunction of one or more regulatory systems. In developing countries, long-term management of patients with chronic diseases has many challenges and is generally not financially viable, but Africa in particular, which is rich in diverse ethnomedicines presents a more feasible long-term therapeutic approach in this niche. However, despite comprehensive preclinical investigations on numerous plant-derived candidate medicines, only a small portion of these reach the patient as recognised medicines. In this review, we use the example of rooibos (Aspalathus linearis (Burm.f.) R. Dahlgren)-which is globally consumed as aromatic, caffeine-free tea-to illustrate the hurdles that need to be overcome in the low-to middle-income countries, before progression of ethnomedicines to official treatment regimens can be achieved. In terms of methodology, regulatory system focused rooibos papers indexed on PubMed for the past three decades (n = 112) were accessed. Papers reporting duplication of previous results were excluded, as well as review papers. Topics covered includes the high standard of ethnomedicine drug discovery and efficacy testing research performed in Africa (and South Africa in particular in the case of rooibos), the potential bias in terms of preclinical research focus, ethnomedicine ownership and the requirement for independent clinical trial coordination and/or management.

The effect of Aspalathin linearis, Cyclopia intermedia and Sutherlandia frutescene on sperm functional parameters of healthy male wistar rats

Introduction: Rooibos (Aspalathin linearis), honeybush (Cyclopia intermedia), and sutherlandia (Sutherlandia frutescene) are three Southern Africa indigenous plants, of which the extracts have become house-hold items and are consumed on a large scale. Although, they are known for their antioxidant properties, studies have highlighted danger in the excessive intake. Therefore, the current study investigated whether treatment with rooibos, honeybush, and sutherlandia will impact sperm functional parameters positively or otherwise, in healthy rats. Methods: Fourteen-week-old pathogen-free adult male Wistar rats (250-300 g) were randomly divided into four groups of ten, including a control, rooibos (RF), honeybush (HB) and a sutherlandia (SL) group. After 7 weeks of treatment, animals were sacrificed. Spermatozoa were retrieved from the cauda epididymis for motility, morphology and concentration analysis and the testis was used for all biochemical assays. Results: The infusion treated animals (RF, HB, and SL) presented with a non-significant decrease of -14.3%, -18.2%, -17.2% and -24.8%, -20.7%, -27.3% in total motility and progressive motility when compared to the control group, respectively. There was a significant increase in number of spermatozoa with slow speed (p = 0.03), especially in SL treated group compared to the control (p = 0.03). Additionally, there was an increase of 28.8%, 31.7%, 23% in superoxide dismutase (SOD) activity of RF, HB and SL compared to control, respectively. This was accompanied with a percentage decrease of -21.1%, -23.7%, 45.9% in malondialdehyde (MDA) levels compared to the control group. Conclusion: In summary, animals treated with the respective infusions presented with a percentage increase in SOD activity but have reduced sperm motility and decreased normal morphology. Paradoxically, they presented with increased sperm concentration. Hence, it is presumed that rooibos, honeybush and sutherlandia may enhance sperm quantity (concentration) but may impair sperm quality (motility morphology) when consumed by healthy animals.

Stimulation of glucose uptake by glycosides from Alectra parasitica subsp. chitrakutensis (M.A. Rau) K.K. Khanna & An. Kumar: An in-vitro study of TNF-α induced insulin resistance in L6 myoblasts

Alectra parasitica subsp. chitrakutensis (M.A. Rau) K.K. Khanna & An. Kumar (Orobanchaceae) is a parasitic plant indigenous to India. Locally, the plant is known as 'Midaki and Nirgundikand'. It is used to treat fever, piles, cardiovascular disorders, and blood-borne non-infectious diseases by ethnic communities. The phytochemical investigation of A. parasitica subsp. chitrakutensis rhizome led to the isolation of azafrin (1), rehmaionoside-C (2), and mussaenoside (3). Compounds (2) and (3) are being reported for the first time from this plant. Compounds were evaluated for their intercellular glucose uptake activity in basal and insulin-TNF-α-stimulated L6 muscle cells. In particular, rehmaionoside C exhibited activity comparative to metformin, increasing uptake by basal- and insulin-TNF-α-stimulated cells by 4.88- and 3.90-fold and 5.04- and 4.04-fold. While azafrin and mussaenoside have produced 3.03- and 2.36-fold; 4.03- and 3.22-fold increase in intercellular glucose uptake. Compounds did not show toxicities in rat L6 myoblast cells. The study suggests that rehmaionoside-C from A. parasitica subsp. chitrakutensis might activate glucose uptake by insulin mimics and could be a nontoxic anti-diabetes lead for drug discovery.

A Review on the Antidiabetic Properties of Moringa oleifera Extracts: Focusing on Oxidative Stress and Inflammation as Main Therapeutic Targets

Moringa oleifera is one of the popular plants that have shown significant health benefits. Certainly, preclinical evidence (predominantly from animal models) summarized in the current review supports the beneficial effects of Moringa oleifera leaf extracts in combating the prominent characteristic features of diabetes mellitus. This includes effective control of blood glucose or insulin levels, enhancement of insulin tissue sensitivity, improvement of blood lipid profiles, and protecting against organ damage under sustained conditions of hyperglycemia. Interestingly, as major complications implicated in the progression of diabetes, including organ damage, Moringa oleifera leaf and seed extracts could efficiently block the detrimental effects of oxidative stress and inflammation in these preclinical models. Notably, these extracts (especially leaf extracts) showed enhanced effects in strengthening intracellular antioxidant defences like catalase, superoxide dismutase, and glutathione to lower lipid peroxidation products and reduce prominent pro-inflammatory markers such as tumor necrosis factor-α, interleukin (1L)-β, IL-6, monocyte chemoattractant protein-1 and nitric oxide synthase. From animal models of diabetes, the common and effective dose of leaf extracts of Moringa oleifera was 100-300 mg/kg, within the treatment duration of 2-8 weeks. Whereas supplementation with approximately 20 g leaf powder of Moringa oleifera for at least 2 weeks could improve postprandial blood glucose in subjects with prediabetes or diabetes. Although limited clinical studies have been conducted on the antidiabetic properties of Moringa oleifera, current findings provide an important platform for future research directed at developing this plant as a functional food to manage diabetic complications.

The triterpene, methyl-3β-hydroxylanosta-9,24-dien-21-oate (RA3), attenuates high glucose-induced oxidative damage and apoptosis by improving energy metabolism

BACKGROUND

Hyperglycemia-induced cardiovascular dysfunction has been linked to oxidative stress and accelerated apoptosis in the diabetic myocardium. While there is currently no treatment for diabetic cardiomyopathy (DCM), studies suggest that the combinational use of anti-hyperglycemic agents and triterpenes could be effective in alleviating DCM.

HYPOTHESIS

To investigate the therapeutic effect of methyl-3β-hydroxylanosta-9,24-dien-21-oate (RA3), in the absence or presence of the anti-diabetic drug, metformin (MET), against hyperglycemia-induced cardiac injury using an in vitro H9c2 cell model.

METHODS

To mimic a hyperglycemic state, H9c2 cells were exposed to high glucose (HG, 33 mM) for 24 h. Thereafter, the cells were treated with RA3 (1 μM), MET (1 μM) and the combination of MET (1 μM) plus RA3 (1 μM) for 24 h, to assess the treatments therapeutic effect.

RESULTS

Biochemical analysis revealed that RA3, with or without MET, improves glucose uptake via insulin-dependent (IRS-1/PI3K/Akt signaling) and independent (AMPK) pathways whilst ameliorating the activity of antioxidant enzymes in the H9c2 cells. Mechanistically, RA3 was able to alleviate HG-stimulated oxidative stress through the inhibition of reactive oxygen species (ROS) and lipid peroxidation as well as the reduced expression of the PKC/NF-кB cascade through decreased intracellular lipid content. Subsequently, RA3 was able to mitigate HG-induced apoptosis by decreasing the activity of caspase 3/7 and DNA fragmentation in the cardiomyoblasts.

CONCLUSION

RA3, in the absence or presence of MET, demonstrated potent therapeutic properties against hyperglycemia-mediated cardiac damage and could be a suitable candidate in the prevention of DCM.

A Meta-Analysis of the Impact of Resveratrol Supplementation on Markers of Renal Function and Blood Pressure in Type 2 Diabetic Patients on Hypoglycemic Therapy

Evidence on the beneficial effects of resveratrol supplementation on cardiovascular disease-related profiles in patients with type 2 diabetes (T2D) is conflicting, while its impact on renal function and blood pressure measurements remains to be established in these patients. The current meta-analysis included randomized controlled trials (RCTs) reporting on the impact of resveratrol supplementation on markers of renal function and blood pressure in patients with T2D on hypoglycemic medication. Electronic databases such as MEDLINE, Cochrane Library, Scopus, and EMBASE were searched for eligible studies from inception up to June 2020. The random and fixed effects model was used in the meta-analysis. A total of five RCTs met the inclusion criteria and involved 388 participants with T2D. Notably, most of the participants were on metformin therapy, or metformin in combination with other hypoglycemic drugs such as insulin and glibenclamide. Pooled estimates showed that resveratrol supplementation in patients with T2D lowered the levels of fasting glucose (SMD: -0.06 [95% CI: -0.24, 0.12]; I2 = 4%, p = 0.39) and insulin (SMD: -0.08 [95% CI: -0.50, 0.34], I2 = 73%, p = 0.002) when compared to those on placebo. In addition, supplementation significantly lowered systolic blood pressure (SMD: -5.77 [95% CI: -8.61, -2.93], I2 = 66%, p = 0.02) in these patients. Although resveratrol supplementation did not affect creatinine or urea levels, it reduced the total protein content (SMD: -0.19 [95% CI: -0.36, -0.02]; I2 = 91%, p = 0.001). In all, resveratrol supplementation in hypoglycemic therapy improves glucose control and lowers blood pressure; however, additional evidence is necessary to confirm its effect on renal function in patients with T2D.

Isoorientin: A dietary flavone with the potential to ameliorate diverse metabolic complications

Isoorientin is a natural C-glucosyl flavone that is generating a lot of interest due to its multiple pharmacological activities. Increasing experimental data have shown that the robust antioxidant and anti-inflammatory properties of isoorientin remain important in ameliorating a number of metabolic complications. In fact, plants rich in isoorientin have demonstrated strong ameliorative properties against complications such as hyperglycemia, hyperlipidemia, and insulin resistance. However, while such evidence is accumulating, it has not been reviewed to better inform on the therapeutic potential of this flavone in improving human health. This review examines and extrapolates available literature on the potential beneficial or detrimental effects associated with the use of isoorientin in mitigating metabolic diseases, with a specific focus on diabetes, obesity, and insulin resistance, including associated complications. The discussion includes effective doses in various experimental settings and proposed molecular mechanisms by which isoorientin may exert its therapeutic effects. In addition, the protective effects of extracts of a number of isoorientin-rich plants against metabolic complications will be highlighted.

The Combination Effect of Aspalathin and Phenylpyruvic Acid-2-O-β-D-glucoside from Rooibos against Hyperglycemia-Induced Cardiac Damage: An In Vitro Study

Recent evidence shows that rooibos compounds, aspalathin and phenylpyruvic acid-2-O-β-d-glucoside (PPAG), can independently protect cardiomyocytes from hyperglycemia-related reactive oxygen species (ROS). While aspalathin shows more potency by enhancing intracellular antioxidant defenses, PPAG acts more as an anti-apoptotic agent. Thus, to further understand the protective capabilities of these compounds against hyperglycemia-induced cardiac damage, their combinatory effect was investigated and compared to metformin. An in vitro model of H9c2 cardiomyocytes exposed to chronic glucose concentrations was employed to study the impact of such compounds on hyperglycemia-induced damage. Here, high glucose exposure impaired myocardial substrate utilization by abnormally enhancing free fatty acid oxidation while concomitantly suppressing glucose oxidation. This was paralleled by altered expression of genes involved in energy metabolism including acetyl-CoA carboxylase (ACC), 5′ AMP-activated protein kinase (AMPK), and peroxisome proliferator-activated receptor-alpha (PPARα). The combination treatment improved myocardial substrate metabolism, maintained mitochondrial membrane potential, and attenuated various markers for oxidative stress including nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and glutathione content. It also showed a much-improved effect by ameliorating DNA damage when compared to metformin. The current study demonstrates that rooibos compounds offer unique cardioprotective properties against hyperglycemia-induced and potentially against diabetes-induced cardiac damage. These data also support further exploration of rooibos compounds to better assess the cardioprotective effects of different bioactive compound combinations.

Dihydrochalcones: Methods of Acquisition and Pharmacological Properties-A First Systematic Review

Dihydrochalcones are a class of secondary metabolites, for which demand in biological and pharmacological applications is still growing. They posses several health-endorsing properties and, therefore, are promising candidates for further research and development. However, low content of dihydrochalcones in plants along with their low solubility and bioavailability restrict the development of these compounds as clinical therapeutics. Therefore, chemomicrobial and enzymatic modifications are required to expand their application. This review aims at analyzing and summarizing the methods of obtaining dihydrochalcones and of presenting their pharmacological actions that have been described in the literature to support potential future development of this group of compounds as novel therapeutic drugs. We have also performed an evaluation of the available literature on beneficial effects of dihydrochalcones with potent antioxidant activity and multifactorial pharmacological effects, including antidiabetic, antitumor, lipometabolism regulating, antioxidant, anti-inflammatory, antibacterial, antiviral, and immunomodulatory ones. In addition, we provide useful information on their properties, sources, and usefulness in medicinal chemistry.

Impact of Cold versus Hot Brewing on the Phenolic Profile and Antioxidant Capacity of Rooibos (Aspalathus linearis) Herbal Tea

Consumption of rooibos (Aspalathus linearis) as herbal tea is growing in popularity worldwide and its health-promoting attributes are mainly ascribed to its phenolic composition, which may be affected by the brewing conditions used. An aspect so far overlooked is the impact of cold brewing vs regular brewing and microwave boiling on the poly(phenolic) profile and in vitro antioxidant capacity of infusions prepared from red ('fermented', oxidized) and green ('unfermented', unoxidized) rooibos, the purpose of the present study. By using an untargeted metabolomics-based approach (UHPLC-QTOF mass spectrometry), 187 phenolic compounds were putatively annotated in both rooibos types, with flavonoids, tyrosols, and phenolic acids the most represented type of phenolic classes. Multivariate statistics (OPLS-DA) highlighted the phenolic classes most affected by the brewing conditions. Similar antioxidant capacities (ORAC and ABTS assays) were observed between cold- and regular-brewed green rooibos and boiled-brewed red rooibos. However, boiling green and red rooibos delivered infusions with the highest antioxidant capacities and total polyphenol content. The polyphenol content strongly correlated with the in vitro antioxidant capacities, especially for flavonoids and phenolic acids. These results contribute to a better understanding of the impact of the preparation method on the potential health benefits of rooibos tea.