ABSTRACT
Whey protein was fortified with a microencapsulated fraction of Stevia rebaudiana, in the proportion 1:4 (w/w), with maltodextrin from the elite variety of Stevia UEM-13, rich in antioxidant compounds, and evaluated its antioxidant and antidiabetic potential in vitro. The fraction in ethyl acetate, the microencapsulated fraction, the whey protein obtained by membrane and a commercial whey protein were characterized and were also investigated solubility, microencapsulation efficiency and stability and digestion in vitro. In addition, these products and two formulations of the icroencapsulated fraction with the obtained whey protein were tested for their potential to inhibit the α-amylase and α-glucosidase enzyme (antidiabetic activity). The microencapsulated fraction (0.5%) and the supplement fortified with the 20% fraction microencapsulated showed inhibitory potential for the enzyme. As for the α-glucosidase enzyme, all products tested showed inhibition, with the formulation with 1.6% microencapsulated fraction added to whey protein being significantly higher. The microencapsulated fraction showed better solubility and stability, including in vitro digestion analysis, and showed antioxidant and antidiabetic capacity. A sensory evaluation was performed with panelists who regularly consume whey protein supplements and products with stevia and the supplement formulation with 1.6 g microencapsulated stevia per 100 g of whey protein have good sensory acceptance.
ABSTRACT
A stevia fraction (ASF) free of steviol glycosides was extracted from Stevia rebaudiana leaves (Stevia UEM-13). ASF essentially constitutes phenolic compounds (52.42%), which were identified by liquid chromatography tandem mass spectrometry (LC-MS/MS) as caffeic acid, quercetin-3-o-glycoside, cyanidin-3-glucoside, kaempferol, quercetin, apigenin, rozmarinic acid, chlorogenic acid and dicaffeoylquinic acid. ASF was used as a multi-functional source of phenolic compounds to fortify the whey protein isolate (WPI) obtained by membrane separation. WPI fortified with 0.2% ASF showed an 80% increase in its antioxidant activity and more pronounced antidiabetic effects than the unfortified WPI, mainly in the glycemic control of diabetic animals induced by streptozotocin. The in vitro and in vivo antioxidant effects of ASF may enhance the effects of WPI. Indeed, this pioneering study revealed that ASF can be used to enrich the antioxidant and antidiabetic properties of WPI.
ABSTRACT
The purpose of this work was to evaluate if the fat liver accumulation interferes with intracellular calcium fluxes and the liver glycogenolytic response to a calcium-mobilizing α(1)-adrenergic agonist, phenylephrine. The animal model of monosodium L-glutamate (MSG)-induced obesity was used. The adult rats develop obesity and steatosis. Calcium fluxes were evaluated through measuring the (45)Ca(2+) uptake by liver microsomes, inside-out plasma membrane, and mitochondria. In the liver, assessments were performed on the calcium-dependent glycogenolytic response to phenylephrine and the glycogen contents. The Ca(2+) uptake by microsomes and plasma membrane vesicles was reduced in livers from obese rats as a result of reduction in the Ca(2+)-ATPase activities. In addition, the plasma membrane Na(+)/K(+)-ATPase was reduced. All these matched effects could contribute to elevated resting intracellular calcium levels in the hepatocytes. Livers from obese rats, albeit smaller and with similar glycogen contents to those of control rats, released higher amounts of glucose in response to phenylephrine infusion, which corroborates these observations. Mitochondria from obese rats exhibited a higher capacity of retaining calcium, a phenomenon that could be attributed to a minor susceptibility of the mitochondrial permeability transition pore opening.
