Potential of rooibos, its majorC-glucosyl flavonoids, andZ-2-(β-D-glucopyranosyloxy)-3-phenylpropenoic acid in prevention of metabolic syndrome

Abstract

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.

Aspalathin from Rooibos (Aspalathus linearis): A Bioactive C-glucosyl Dihydrochalcone with Potential to Target the Metabolic Syndrome

“…On the other hand, a hot water extract (aspalathin content < 2 %) of fermented rooibos [26] is more economical to produce and it is preferred in food products, such as rooibos iced tea, when the flavour is important [27]. Similarly, green rooibos infusions at "cupof-tea" strength have a much higher aspalathin content (78-251 mg/L) [28] than fermented rooibos infusions (not detected-16 mg/L) [29]. The bulk of rooibos production is processed to supply the demand for the traditional "fermented" herbal tea product [22].…”

Investigating the Physicochemical Properties and in Vitro Bioaccessibility of Phenolics and Antioxidant Capacity of Rooibos Herbal Tea Beverage

“…Additionally, benefical effects of rooibos especially its anti-diabetic properties is focused on its major flavonoid dihydrochalcone aspalathin. While fresh leaves of rooibos contain polyphenols as flavanols, dihydrochalcones and aspalathin, processed leaves and stem include benzoic and cinnamic acid (Muller et al, 2016). Additionally, anti-cancer properties of rooibos demonstrated in rat liver, oesophagus, and skin carcinogenesis models, have been attributed to their polyphenolic compounds (Marnewick et al, 2009;Sissing et al, 2011).…”

Differential Modulation of Gene Expression Encoding Hepatic and Renal Xenobiotic Metabolizing Enzymes by an Aspalathin-Enriched Rooibos Extract and Aspalathin

“…Based on 1.2 mg aspalathin/200 mL of a fermented rooibos infusion equaling 1 cup [43], humans (70 kg BW) consuming 6 cups of rooibos per day, as suggested by Marnewick et al [44], have a daily intake of 0.1 mg aspalathin/kg. When consuming 6 cups of green rooibos infusion at 31 mg aspalathin/200 mL [5], the daily intake of aspalathin will equal 2.7 mg/kg BW. This is approximately 13-fold lower when compared to the current exposure in rats and two-fold lower when considering the HED.…”

“…R.Dahlgren, Leguminosae), has become increasingly popular for its unique flavor and health promoting properties [4]. For the production of nutraceutical extracts, especially those with antidiabetic properties, the "unfermented" product (green rooibos) is preferred due to the high levels of the antioxidant and antidiabetic [5] dihydrochalcone, aspalathin (▶ Fig. 1).…”