Isolation and Characterization of a Novel Rebaudioside M Isomer from a Bioconversion Reaction of Rebaudioside A and NMR Comparison Studies of Rebaudioside M Isolated from Stevia rebaudiana Bertoni and Stevia rebaudiana Morita

• Main Authors: Indra Prakash, Cynthia Bunders, Krishna P. Devkota, Romila D. Charan, Catherine Ramirez, Christopher Priedemann, Avetik Markosyan
• Format: Article
• Language: English
• Published: MDPI AG 2014-03-01
• Series: Biomolecules
• Subjects: Stevia rebaudiana Bertoni; Stevia rebaudiana Morita; rebaudioside M; rebaudioside D; rebaudioside M2; bioconversion; steviol glycosides; structure characterization; nuclear magnetic resonance (NMR)
• Online Access: http://www.mdpi.com/2218-273X/4/2/374

A minor product, rebaudioside M2 (2), from the bioconversion reaction of rebaudioside A (4) to rebaudioside D (3), was isolated and the complete structure of the novel steviol glycoside was determined. Rebaudioside M2 (2) is considered an isomer of rebaudioside M (1) and contains a relatively rare 1→6 sugar linkage. It was isolated and characterized with NMR (1H, 13C, COSY, HSQC-DEPT, HMBC, 1D-TOCSY, and NOESY) and mass spectral data. Additionally, we emphasize the importance of 1D and 2D NMR techniques when identifying complex steviol glycosides. Numerous NMR spectroscopy studies of rebaudioside M (1), rebaudioside D (3), and mixture of 1 and 3 led to the discovery that SG17 which was previously reported in literature, is a mixture of rebaudioside D (3), rebaudioside M (1), and possibly other related steviol glycosides.