Structural Elucidation of Quinovose-Containing Steviol Glycosides from Enzymatic Biotransformation of Stevia rebaudiana

TL;DR

Researchers identified two new sweet compounds from Stevia rebaudiana, offering insights into the plant's chemical diversity and potential for better sweeteners.

Contribution

Discovery of two novel quinovose-containing steviol glycosides, Rebaudioside QM and 2QM, and their proposed biosynthetic pathways.

Findings

Rebaudioside QM and 2QM were isolated and structurally characterized using NMR and MS.

Stevioside E is hypothesized as a biosynthetic precursor for Rebaudioside QM.

LC-MS profiling suggests potential precursors for Rebaudioside 2QM.

Abstract

Two steviol glycosides containing quinovose were isolated from a biotransformation mixture of stevia extract derived from Stevia rebaudiana Bertoni leaves. These compounds were elucidated using comprehensive spectroscopic techniques, including nuclear magnetic resonance (NMR) and mass spectrometry (MS). These compounds were designated as Rebaudioside QM and the novel Rebaudioside 2QM. Based on structural similarity, we hypothesize that Stevioside E may serve as a biosynthetic precursor for Rebaudioside QM. Comprehensive LC-MS profiling also suggests potential precursors for Rebaudioside 2QM. Tentative biosynthetic pathways were proposed for both compounds. The presence of these unknown compounds further supports the notion that S. rebaudiana harbours a wide array of yet-undiscovered steviol glycosides, potentially driven by the inherent diversity of UDP-dependent glycosyltransferases (UGTs) within the plant itself. The discovery of Rebaudioside QM and Rebaudioside 2QM expands the known diversity of steviol glycosides and provides new insights into glycosylation patterns in S. rebaudiana, which may support the development and production of novel sweeteners with improved sensory and physicochemical properties.

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