Cereus peruvianus Mill. (Cactaceae) as a source of natural antioxidants: Phenolic compounds and antioxidant activity of cladode extracts in two collection periods.

The economic potential of the cactus species Cereus peruvianus Mill. (syn. C. hildmannianus K. Schum.) has already been demonstrated through the generation of products and patents. However, the phenolic compounds and antioxidant activity have not yet been evaluated. The aim of our study was to determine the total phenolic compounds, evaluate the antioxidant activity and characterize the phenolic compounds of cladode extracts from C. peruvianus grown in the southern region of Brazil, in two collection periods. Higher total content of phenolic compounds and antioxidant activity were detected in the cladode extract collected in 2016 than in the cladode extract collected in 2015. The profile of phenolic compounds identified five flavonoids that had not previously been reported in species of the genus Cereus. The phenolic compounds linked to antioxidant activities identified in the cladode extract from C. peruvianus support the use of this species in human food as a source of natural antioxidants.

Pretreatment with ethanol as an alternative to improve steviol glycosides extraction and purification from a new variety of stevia.

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.

Fortification of the whey protein isolate antioxidant and antidiabetic activity with fraction rich in phenolic compounds obtained from Stevia rebaudiana (Bert.). Bertoni leaves.

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.