Endocyclic double bond isomers and by-products from rebaudioside A and stevioside formed under acid conditions

Publication date: June 2018 Source:Phytochemistry Letters, Volume 25 Author(s): Wilmer H. Perera, Maite L. Docampo, Frank T. Wiggers, Charles D. Hufford, Frank R. Fronczek, Bharathi Avula, Ikhlas A. Khan, James D. McChesney The hydrolysis reaction of rebaudioside A and stevioside was studied under mild and strong acidic conditions at different temperatures and times. Exposure of rebaudioside A to vigorous acid conditions yielded three different aglycone cores which were purified by silica gel chromatography: compound 1 (isosteviol), 2 (steviol) and 3 (endocyclic isomer of steviol). Four new glucoside degradation products with an ent-kaur-15-en-19-oic acid skeleton together with three known compounds were obtained after mild acid hydrolysis from rebaudioside A and stevioside. Compounds were identified based on extensive 1D and 2D NMR measurements and/or MS/MS fragmentation: compound 4 (Endo-steviolmonoside), compound 5:(Endo-rebaudioside G1), compound 6 (Endo-steviolbioside) and compound 7 (Endo-rubusoside) while compounds 8–10 were identified as iso-rebaudioside A (Endo-rebaudioside A) (8), iso-rebaudioside B (Endo-rebaudioside B) (9) and iso-stevioside (Endo-stevioside) (10). Crystal structure determination of compound 3 and 6 allowed confirmation of their structures by X-ray diffraction. Acidic beverages based on steviol glycosides as sugar substitutes should be properly storage for avoiding the loss of their organoleptic properties by formation of these or othe...

Source: Phytochemistry Letters - April 14, 2018 Category: Chemistry Source Type: research