Steviol glycosides are extracted from the leaves of the plant species Stevia rebaudiana, they are the natural constituents that are used as sweeteners in foods and beverages. Some of the more common steviol glycosides include Stevioside and Rebaudioside A1.
Shin, Dong Hee et al. Glycemic Effects of Rebaudioside A and Erythritol in People with Glucose Intolerance. Diabetes & metabolism journal vol. 40,4 (2016): 283-9. doi:10.4093/dmj.2016.40.4.283.