Stevia rebaudiana Bertoni is a shrub having a high content of sweet diterpenoid glycosides in its leaves, mainly stevioside and rebaudioside A, which are used as noncaloric, natural sweeteners. The aim of this study was to deepen the knowledge about the insulin-mimetic effect exerted by four different mixtures of steviol glycosides, rich in stevioside and rebaudioside A, in neonatal rat cardiac fibroblasts. The potential antioxidant activity of these steviol glycosides was also assessed, as oxidative stress is associated with diabetes. Likewise the insulin effect, steviol glycosides caused an increase in glucose uptake into rat fibroblasts by activating the PI3K/Akt pathway, thus inducing Glut4 translocation to the plasma membrane. The presence of S961, an insulin antagonist, completely abolished these effects, allowing to hypothesize that steviol glycosides could act as ligands of the same receptor engaged by insulin. Moreover, steviol glycosides counteracted oxidative stress by increasing reduced glutathione intracellular levels and upregulating expression and activity of the two antioxidant enzymes superoxide dismutase and catalase. The present work unravels the insulin-mimetic effect and the antioxidant property exerted by steviol glycosides, suggesting their potential beneficial role in the cotreatment of diabetes and in health maintenance.

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Glycosides from Stevia rebaudiana Bertoni Possess Insulin-Mimetic and Antioxidant Activities in Rat Cardiac Fibroblasts.

Pressurized hot water extraction (PHWE) for the green recovery of bioactive compounds and steviol glycosides from Stevia rebaudiana Bertoni leaves

Stevia rebaudiana is a nutrient rich natural sweetest plant of Asteraceae family. The leaves naturally contain diterpene glycosides stevioside, rebaudiosides A-F, steviolbioside and dulcoside, which are responsible for its sweet taste and have commercial value all over the world as sugar substitute in foods, beverages or medicines. It is a plant which offers sweetness with fewer calories and do not show any side effects after consumption on human health. Stevia has many pharmacological and therapeutic applications as suggested by many preclinical and some clinical studies; these are nontoxic and possess antioxidant, antimicrobial, antifungal and anticarcinogenic activity. In future Stevia is likely to become a major source of high potency low calorie sweetener for growing natural food market. This review article presents beneficial role of Stevia and its metabolites on health promoting properties.

	 

	Key words: Stevia rebaudiana, steviosides, sweetner.

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Nutritional and therapeutic values of Stevia rebaudiana: A review

The aim of the presented study was to characterize the content and biological activity of extracts prepared from dried Stevia rebaudiana leaves with potential application in the food or cosmetic industry. Aqueous (A), ethanolic (E) and glycol-aqueous (GA) extracts were analyzed for the content of polyphenols and proteins, showing that the highest amount of phenols (15.50 mg/g) and flavonoids (3.85 mg/g) contained GA. All extracts contained significant amount of protein (69.40–374.67 mg/g). Between analyzed stevia extracts (HPLC) GA contained the highest amount of polyphenols, especially ferulic (5.50 mg/g) and rozmaric (4.95 mg/g) acids derivates. The highest antiradical activity against DPPH• and ABTS•+ was noted for GA and E (IC50 = 0.38 and 0.71 µg flavonoids/mL). The highest ability to chelate Fe2+ was observed for E (IC50 = 2.08 µg flavonoids/mL). Stevia extracts were also analyzed for their cytotoxicity and fibroblast irritation potential in vitro. E and GA were the most cytotoxic and irritating, probably due to the high content of biologically active phytochemicals. On the other hand, a extract was the most tolerable by the cells. To summarize, the presented study evaluated the potential application of A, E and GA stevia extracts as natural source of antioxidants in the food and cosmetic industry.

Stevia rebaudiana Bert. leaf extracts as a multifunctional source of natural antioxidants

Response surface methodology to optimise Accelerated Solvent Extraction of steviol glycosides from Stevia rebaudiana Bertoni leaves

article i nfo Background: Stevia rebaudiana Bertoni has been used for the treatment of diabetes in, for example, Brazil, although a positive effect on antidiabetic and its complications has not been unequivocally demonstrated. This herb also has numerous therapeutic properties which have been proven safe and effective over hundreds of years. Streptozotocin is a potential source of oxidative stress that induces genotoxicity. Objective: We studied the effects of stevia leaves and its extracted polyphenols and fiber on streptozotocin induced diabetic rats. We hypothesize that supplementation of polyphenols extract from stevia to the diet causes a reduction in diabetes and its complications. Design/Methods: Eighty Wistar rats were randomly divided into 8 groups; a standard control diet was supplemented with either stevia whole leaves powder (4.0%) or polyphenols or fiber extracted from stevia separately and fed for one month. Streptozotocin (60 mg/kg body weight, i.p) was injected to the diabetic groups on the 31st day. Several indices were analyzed to assess the modulation of the streptozotocin induced oxidative stress, toxicity and blood glucose levels by stevia. Results: The results showed a reduction of blood glucose, ALT and AST, and increment of insulin level in the stevia whole leaves powder and extracted polyphenols fed rats compared to control diabetic group. Its feeding also reduced the MDA concentration in liver and improved its antioxidant status through antioxidant enzymes. Glucose tolerance and insulin sensitivity were improved by their feeding. Streptozotocin was also found to induce kidney damage as evidenced by decreased glomerular filtration rate; this change was however alleviated in the stevia leaves and extracted polyphenol fed groups. Conclusion: The results suggested that stevia leaves do have a significant role in alleviating liver and kidney damage in the STZ-diabetic rats besides its hypoglycemic effect. It might be adequate to conclude that stevia leaves could protect rats against streptozotocin induced diabetes, reduce the risk of oxidative stress and ameliorate liver and kidney damage.

http://biostevera.com/wp-content/uploads/2014/11/11-Antioxidant-anti-diabetic-and-renal-protective-properties-of-Stevia-rebaudiana.pdf

Antioxidant, anti-diabetic and renal protective properties of Stevia rebaudiana

When people are exposed to the extreme environmental conditions, such as high altitude (HA) where there is decrease in temperature and partial pressure of oxygen induces fatigue, insomnia, loss of appetite and increased cardiac output. Hence there is need to improve the appetite through the diet and digestion clout of the individual. In the present review paper we have discussed the efficiency of digestion is compromised at HA. Also about, Hypoxia, resulting by decreased partial pressure of oxygen can be classified into acute hypoxia and chronic hypoxia based on the exposure time. There is increased formation of reactive oxygen species (ROS) due to less oxygen available in the air at HA which leads to oxidative stress. Lipid peroxidation caused by oxidative stress. Hypoxia is mediated through hypoxia inducible factors which maintain oxygen haemostasis in the body. At HA diet rich in carbohydrates have been found to be beneficial as it increases glucose metabolism. Requirement of nutrients such as vitamin A, vitamin E and vitamin C as well as micronutrients such as zinc, iron, selenium, copper and manganese will be required at HA. Hypoxia effect on the intestine leads to malabsorption and the lipid storage is stimulated and lipid catabolism is inhibited through β-oxidation.

http://publications.drdo.gov.in/ojs/index.php/dlsj/article/download/11371/5880

Naveen Shivanna

Papers

Antioxidant, anti-diabetic and renal protective properties of Stevia rebaudiana

Nutritional requirement at high-altitude with special emphasises to behaviour of gastro-intestinal tract and hormonal changes