Helenin from Stevia lucida. The first report of this natural eudesmanolide mixture in Eupatorieae tribe

From aerial parts of Stevia lucida Lagasca was isolated the natural mixture of isomeric eudesmanolides helenin. The identification and quantification of the constituents of helenin (alantolactone 1 and isoalantolactone 2, ratio 3:7) was performed through the quantitative analysis of its 1D and 2D NMR spectra.