Antioxidation and Antiglycation Properties of a Natural Sweetener: Stevia rebaudiana

Stevia rebaudiana, a natural sweetener and a non-caloric sugar substitute, is known to exhibit several medicinal properties including anti-diabetic effects. However, its mechanism of action, as an antidiabetic agent, is not completely understood. In this study, aqueous, methanol, and ethanol extracts of leaves were used. Among all the extracts, the methanolic extract exhibited the highest TPC (41.00 ± 0.69 mg GAE/g DW), TFC (22.66 ± 0.036 mg QE/g DW), FRAP activity (2.50 ± 0.09 mmol of Fe2+/g DW) along with lowest IC50 values for ABTS (3.8 ± 0.01 µg/mL), and nitric oxide radical scavenging activity (150 ± 0.05 µg/mL), whereas ethanolic extract showed the lowest IC50 value of 41 ± 0.20 µg/mL against DPPH than the aqueous (80 ± 0.09 µg/mL) and methanolic (70 ± 0.10 µg/mL). However, aqueous extract showed a strong correlation between phenolic content and antioxidant capacities with R2 values of 0.961 (DPPH), 0.990 (ABTS), and 0.916 (nitric oxide) assays, respectively. Additionally, the aqueous extract inhibited 17.41 ± 0.11% activity of α-amylase and 8.30 ± 0.95% of α-glucosidase. Moreover, the antiglycation properties of the aqueous extract were confirmed with observations like reduction in browning (34.95 ± 11.09%), fructosamine formation (80 ± 5.12%), carbonyl content (11.68 ± 2.12%), and protein aggregation, in an in vitro glycation system. Furthermore, the extract showed high efficiency in protection against H2O2-induced DNA damage. It can also be used as a source of antiglycation and antioxidant agent for the management of glycation-induced disorders like diabetes. This report also shows a positive correlation between phytochemicals present in the Stevia and their associated antioxidant power. Moreover, these antioxidant compounds can prevent the consequences of AGEs formation.