The potential antidiabetic properties of green and purple tea [Camellia sinensis (L.) O Kuntze], purple tea ellagitannins, and urolithins.

ETHNOPHARMACOLOGICAL RELEVANCE: Tea (Camellia sinensis) has been consumed for centuries as traditional medicine for various diseases, including diabetes. The mechanism of action of many traditional medicines, including tea, often requires elucidation. Purple tea is a natural mutant of Camellia sinensis, grown in China and Kenya, and is rich in anthocyanins and ellagitannins. AIM OF THE STUDY: Here we aimed to determine whether commercial green and purple teas are a source of ellagitannins and whether green and purple teas, purple tea ellagitannins and their metabolites urolithins have antidiabetic activity. MATERIALS AND METHODS: Targeted UPLC-MS/MS was employed to quantify the ellagitannins corilagin, strictinin and tellimagrandin I, in commercial teas. The inhibitory effect of commercial green and purple teas and purple tea ellagitannins was evaluated on α-glucosidase and α-amylase. The bioavailable urolithins were then investigated for additional antidiabetic effects, by evaluating their effect on cellular glucose uptake and lipid accumulation. RESULTS: Corilagin, strictinin and tellimagrandin I (ellagitannins) were identified as potent inhibitors of α-amylase and α-glucosidase, with Ki values significantly lower (p < 0.05) than acarbose. Commercial green-purple teas were identified as ellagitannin sources, with especially high concentrations of corilagin. These commercial purple teas, containing ellagitannins, were identified as potent α-glucosidase inhibitors with IC50 values significantly lower (p < 0.05) than green teas and acarbose. Urolithin A and urolithin B were as effective (p> 0.05) as metformin in increasing glucose uptake in adipocytes, muscle cells and hepatocytes. In addition, similar (p > 0.05) to metformin, both urolithin A and urolithin B reduced lipid accumulation in adipocytes and hepatocytes. CONCLUSIONS: This study identified green-purple teas as an affordable widely available natural source with antidiabetic properties. Furthermore, additional antidiabetic effects of purple tea ellagitannins (corilagin, strictinin and tellimagrandin I) and urolithins were identified.

Whole blood ultrastructural alterations by mercury, nickel and manganese alone and in combination: An ex vivo investigation.

The distribution of metals across the environment is increasingly becoming a major concern as they not only pollute the environment but also pose a danger to humans and animals. Human exposure to heavy metals often occurs as a combination of metals the synergistic effects of which can be more toxic than a single metal. The aim of this study was to investigate the effects that the metals mercury (Hg), nickel (Ni) and manganese (Mn) alone and in combination have on erythrocyte morphology and other components of the coagulation system using the haemolysis assay, scanning electron microscopy (SEM), and confocal laser scanning microscopy. Human blood was exposed to the heavy metals ex vivo, and percentage haemolysis was determined. Ultrastructural analysis of erythrocytes, platelets and fibrin networks was performed using SEM. Analysis of phosphatidylserine (PS) flip-flop was determined using confocal laser scanning microscopy. At the highest concentration of 10,000× the World Health Organization safety limit, all the metals caused haemolysis. The results showed that the exposure of erythrocytes to Hg alone and in combination with other metals displayed more haemolysis compared to Ni and Mn alone and in combination. Components of the coagulation system showed ultrastructural changes, including the formation of echinocytes and the activation of platelets with all single metals as well as the combinations. Confocal laser scanning microscopy analysis showed the presence of PS on the outer surface of the echinocytes that were exposed to metals alone and in combination. It can, therefore, be concluded that these heavy metals have a negative impact on erythrocytes and the coagulation system.

The impact of boiling and in vitro human digestion of Solanum nigrum complex (Black nightshade) on phenolic compounds bioactivity and bioaccessibility.

Solanum nigrum complex (Black nightshade) is a wild leafy vegetable with phenolic antioxidant compounds related to the reduction of oxidative stress. Changes in phenolics and bioactivity due to cooking and gastrointestinal digestion of black nightshade were compared to spinach. Predominant compounds of black nightshade were myricetin, quercetin-3-O-robinoside, 3,4-dicaffeoylquinic acid, 3-caffeoylquinic acid, and rutin, which were improved after boiling but reduced after in vitro digestion. Phenolics were reduced after digestion of black nightshade and spinach; however, bioactivity was still retained, especially in preventing oxidative stress in Caco-2 cells. Hence, indicating their potential to reduce oxidative stress related diseases of the digestive tract.

Influence of boiling and subsequent phases of digestion on the phenolic content, bioaccessibility, and bioactivity of Bidens pilosa (Blackjack) leafy vegetable.

The effects of boiling and in vitro human simulated digestion on phenolic compounds and bioactivity of the African leafy green vegetable, Bidens pilosa, known as Blackjack in South Africa, was investigated and compared to the leafy green vegetable Spinacia oleracea (Spinach). Metabolites such as 3-caffeoylquinic acid, catechin, 4-caffeoylquinic acid, quercetin-3-O-robinobioside, rutin and quercetin-3-O-glucoside were dominant in the boiled methanolic compared with the raw methanolic extracts of the Blackjack. The total phenolic and flavonoid content generally decreased after in vitro complete digestion for both raw and boiled extracts, indicating that pH and environment associated with digestion alters the bioactivity of the extracted phenolics. Both leafy green vegetables had beneficial effects, but all Blackjack extracts were more effective in preventing the AAPH-mediated oxidation of Caco-2 cells, low-density lipoprotein and deoxyribonucleic acid than those of the spinach. This study identified the health benefits of eating Blackjack and therefore, the cultivation and consumption of this leafy green vegetable should be promoted.

Oxidative and haemostatic effects of copper, manganese and mercury, alone and in combination at physiologically relevant levels: An ex vivo study.

Water contamination with metals due to anthropogenic activity is increasing and subsequent exposure increases the risk of associated toxicity. Exposure is not limited to a single metal but usually involves mixtures of different metals at different concentrations. Little is known about the contribution of this type of exposure, in humans, to the development of non-communicable diseases such as cardiovascular disease, and an increased risk to thrombosis. The World Health Organization has established limits for metal levels in drinking water and this includes levels for copper (Cu), manganese (Mn) and mercury (Hg). In this study, at 100X these limits, the ability of the metals' oxidative effects as catalysts of the Fenton reaction and/or ability to bind glutathione (GSH) were determined. The haemostatic effects of these metals, alone and in combination, at the World Health Organization limit were then evaluated. The ultrastructural and viscoelastic alterations of exposed ex vivo whole blood were also evaluated using scanning electron microscopy and thromboelastography® (TEG), respectively. Cu, alone and in combination with Mn and/or Hg, induced hydroxyl radical formation and reduced GSH levels. Ex vivo exposure caused deformation of erythrocytes and accelerated platelet activation especially for Cu, alone and in combination, with Mn. Reduction in the lysis potential of the clot was also observed for all combinations, especially Cu in combination with Hg as well as Mn alone. Although the TEG findings were not statistically significant, the trends indicate that the exposure to these metals, alone and in combination, adversely affects thrombus formation in ex vivo blood, thereby potentially increasing the risk in exposed individuals for thrombosis.