TRANSGLYCOSYLATION OF STEVIOSIDE AND BIOCHEMICAL AND PHYSIOLOGICAL EVALUATION COMPARED TO NATURAL AND ARTIFICIAL SWEETENERS

The increasing occurrence of metabolism-related diseases, such as obesity and diabetes, encouraged the consumption of high-intensity sweeteners, which can be natural or artificial, and preferentially non-caloric. The plant Stevia rebaudiana is a source of steviol glycosides, among which stevioside and rebaudioside A are highlighted. Stevioside, due to its bitter aftertaste that consequently restricts its use, has been processed by some enzymatic methodologies that enhance its sensory profile. In this study, a transglycosylation reaction catalyzed by the enzyme cyclodextrin glycosyltransferase (CGTase) was performed and the methodology involves carbohydrate molecules from the donor substrate, maltodextrin, which are hydrolyzed and transferred to stevioside at positions C13 and C19 of the steviol skeleton. Stevioside and transglycosylated products were identified by Liquid Chromatography-Mass Spectrometry (LC-MS). The presence of stevioside and steviol glycosides with one, two or three glucose molecules attached was confirmed in the product obtained with CGTase. The conversion rate of stevioside was 70%. Transglycosylation produced a mixture of enzymatically modified products with less bitter aftertaste compared to stevioside. A total of 86% of the tasters who underwent sensory testing preferred these modified products, suggesting that they could be used as low-calorie sweeteners. The transglycosylated product was tested in regard to its effects. Initially, the acute study was conducted on glucose through a venous infusion and the modified product did not affect significantly plasma glucose concentrations and did not interfere with the glucose tolerance test (GTT). The chronic study administrated the transglycosylated, stevioside and other sweeteners in 55-day-old male Wistar rats separated into 5 groups: Control, Stevioside, Transglycosylated, Saccharin and Cyclamate, and Sucrose. Each group received its respective treatment and the doses were determined by the Brazilian Diabetes Society and the World Health Organization (WHO).
Physiological and biochemical parameters were analyzed and were submitted to analysis of variance (ANOVA), followed by the Tukey test. The program GraphPad Prism, version 7.0, was used and the results were presented as the average ± standard error of the mean (SEM). The transglycosylation reaction yielded 43.66%. The parameters of water intake, in vitro and in vivo antioxidant activity, total cholesterol, aspartate aminotransferase, alanine aminotransferase and fructosamine presented significant differences between some groups. However, body weight, food intake, glycemic profile, triglycerides and organ analysis did not present significant differences. In conclusion, enzymatic modification of stevioside is viable and can be an alternative to table-top sweeteners because it can improve the sensorial profile of this steviol glycoside and can be consumed by individuals who want to prevent themselves from these metabolic syndromes and by carriers of these disorders, without losing its biochemical and physiological properties, in addition to the positive effect in the treatment and control of oxidative stress.