Diterpene glycosides from Stevia phlebophylla A. Gray

•The rare species Stevia phlebophylla A. Gray was investigated.•Previous research showed the presence of the highly sweet stevioside.•No such indications were found after extensive MS and NMR analyses.•Instead, a new ent-kaurene glycoside was identified while seven more were indicated.•Stevia rebaudiana likely remains the only known Stevia species synthesizing steviol glycosides.

The rare Mexican species Stevia phlebophylla A. Gray was long considered to be the only known Stevia species, beside the well-known S. rebaudiana, containing the highly sweet diterpenoid steviol glycosides. We report a re-evaluation of this claim after phytochemically screening leaves obtained from two herbarium specimens of S. phlebophylla for the presence of steviol glycosides. Despite extensive MS analyses, no steviol glycosides could be unambiguously verified. Instead, the main chromatographic peak eluting at retention times similar to those of steviol glycosides was identified as a new compound, namely 16β-hydroxy-17-acetoxy-ent-kauran-19-oic acid-(6-O-β-d-xylopyranosyl-β-d-glucopyranosyl) ester (1) on the basis of extensive NMR and MS data as well as the characterization of its acid hydrolysate. Seven more compounds were detected by ESIMS which are possibly structurally related to 1. It can therefore be concluded that S. phlebophylla is unlikely to contain significant amounts of steviol glycosides, if any.

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