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Leaves of a new variety of Stevia rebaudiana with a high content of rebaudioside A were pretreated with ethanol. The ethanolic extract showed high antioxidant potential and 39 compounds were identified, by UPLC/HRMS, among them one not yet mentioned in the literature for stevia leaves. From the in natura leaves and pretreated leaves, the conditions of aqueous extraction of steviol glycosides were investigated using response surface methodology. The aqueous extracts obtained were purified by ion exchange chromatography techniques and membrane separation methods. The recuperation of steviol glycosides was 4.02g for pretreated leaves and 2.20g for in natura leaves. The level of purity was, respectively, 87% and 84.8%. The results obtained demonstrate that pretreatment increases the yield and purity level of stevia sweeteners by the use of environmentally friendly methodologies and the final product presented acceptable sensory characteristics.

This work aimed to formulate and perform physicochemical and functional characterization of maltodextrin microcapsules containing ethanolic extract of stevia, rich in antioxidant compounds, encapsulated by a spray-drying process with two maltodextrins (DE10 and DE19). The powders were named M10 and M19, respectively. We analyzed the physicochemical parameters, antidiabetic activity, cytotoxicity, bioaccessibility of the compounds by in vitro digestion, as well as the structure of the microcapsules by scanning electron microscopy. Microcapsules showed higher solubility (∼35%), lower moisture content (∼29%), and the maltodextrin DE10 had higher efficiency as an encapsulating agent (87%) when compared to DE19 (76%) and showed well-defined spherical structures. The microencapsulation preserved the content of phenolic compounds and antioxidant activity present in the extract (7.2% and 87.5%, respectively). The bioaccessibility of these microencapsulated compounds and antioxidant activity were higher under different conditions of in vitro digestion (mouth, gastric, and intestinal conditions) and showed no cytotoxic effects. We identified 41 compounds (by UHPLC-MS/MS-Qtof) related to the nutritional benefits offered by stevia and the microencapsulation technique can be recommended to preserve bioactive compounds.

The aim of this study was to determine the composition and antioxidant potential of leaves of a new variety of Stevia rebaudiana (Stevia UEM-13). Stevia leaves of UEM-13 contain rebaudioside A as the main glycoside, while most wild Stevia plants contain stevioside. Furthermore can be multiplied by seed, which reduces the cost of plant culture techniques as other clonal varieties are multiplied by buds, requiring sophisticated and expensive seedling production systems. Ethanol and methanol were used in the extraction to determine the bioactive compounds. The methanolic extract was fractionated sequentially with hexane, chloroform, ethyl acetate and isobutanol, and the highest concentration of phenolic compounds and flavonoids was obtained in the ethyl acetate fraction (524.20 mg galic acid equivalent/g; 380.62 µg quercetin equivalent/g). The glycoside content varied greatly among the fractions (0.5% -65.3%). Higher antioxidant potential was found in the methanol extract and the ethyl acetate fraction with 93.5% and 97.32%, respectively. In addition to being an excellent source for obtaining of extracts rich in glycoside, this new variety can also be used as raw material for the production of extracts or fractions with a significant amount of antioxidant activity and potential to be used as additives in food.

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Objective: To develop a natural dietary product with functional benefits for diabetic patients. Whey protein concentrate was obtained through the separation membrane processes and sweetened with rebaudioside A. This product was submitted to sensory testing in humans and used to evaluate possible functional properties in male Wistar rats models with diabetesMellitus induced by streptozotocin. Methods: Two concentrates were produced. Only the second showed protein content of 74.3 and 17.3% of lactose was used as supplementation in induced diabetic rats. This concentrate was obtained from the concentration by reverse osmosis system (180 k Daltons), followed by nanofiltration in a 500 k Daltons membrane and spray drying at 5.0% solution of the first concentrate developed. The concentrate was sweetened with rebaudioside A (rebaudioside A 26 mg/100 g concentrate). All procedures were performed at the Center for Studies in Natural Products, at the Universidade Estadual de Maringá. Three experimental groups were established (n=6): two groups of diabetic animals, one control group and one supplemented group; and a control group of normal mice (non-diabetic). The supplemented group received concentrates sweetened with rebaudioside A in a dose of 100 mg/kg bw/day by an esophageal tube for 35 days. Fasting, the fed state and body weight were assessed weekly for all groups. At the end of the supplementation period, the following were analyzed: plasma parameters of glucose, total cholesterol, triglycerides and fructosamine; the serum levels of aspartate aminotransferase and alanine aminotransferase, water and food intake. Organs and tissues were removed and weighed to assess mass and anatomical changes. Results: The product presented 74% of proteins and 17% of lactose and showed satisfactory sensory testing by the addition of 26 mg of rebaudioside A/100 g concentrate. Supplementation of the product reduced hyperglycemia, plasma fructosamine levels, triglycerides and total cholesterol, and improved body weight gain of streptozotocin-induced diabetic rats. Conclusion: Whey protein concentrate with substantial content of protein (above 70%) and low lactose was obtained through the membrane separation processes. The addition of rebaudioside A at the concentration of 26 mg/100 g rebaudioside A proved to be as sweet as sucralose with satisfactory sensory testing, which indicates that this is a non-caloric natural sweetener that can replace artificial sweeteners. The product (whey protein concentrate sweetened with rebaudioside A) presented important functional properties and reduced the metabolic disorders caused by the syndrome.

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Stevia rebaudiana (Bert.) Bertoni besides being a source of noncaloric sweeteners is also an important source of bioactive molecules. Many plant extracts, mostly obtained with ethyl acetate solvent, are rich in polyphenol compounds that present insulinotropic effects. To investigate whether the nonsweetener fraction, which is rich in phenolic compounds isolated from Stevia rebaudiana with the solvent ethyl acetate (EAF), has an insulinotropic effect, including interference at the terminals of the autonomic nervous system of the pancreatic islets of rats. Pancreatic islets were isolated from Wistar rats and incubated with EAF and inhibitory or stimulatory substances of insulin secretion, including cholinergic and adrenergic agonists and antagonists. EAF potentiates glucose-stimulated insulin secretion (GSIS) only in the presence of high glucose and calcium-dependent concentrations. EAF increased muscarinic insulinotropic effects in pancreatic islets, interfering with the muscarinic receptor subfamily M3. Adrenergic inhibitory effects on GSIS were attenuated in the presence of EAF, which interfered with the adrenergic α 2 receptor. Results suggest that EAF isolated from stevia leaves is a potential therapy for treating type 2 diabetes mellitus by stimulating insulin secretion only in high glucose concentrations, enhancing parasympathetic signal transduction and inhibiting sympathetic signal transduction in beta cells.