Isolation and identification of progenitors, glycoconjugates of β-damascenone precursors, in sweet potato (Ipomoea batatas)

β-Damascenone, which has a characteristic sweet and fruity aroma, is a key flavour of various food and drinks, including sweet potato shochu, a Japanese traditional spirit. The compound in the spirits is known to be hydrolytically generated and liberated from progenitors in sweet potato during the manufacturing processes. However, thus far, the progenitors have not been well investigated. In this study, we isolated and identified 11 glycosidic progenitor compounds 1–11 using various chromatographic and spectroscopic techniques combined with a hydrolysis assay. These progenitors consist of two types of aglycones [3,5,9-trihydroxymegastigma-6,7-diene (A1) and 3,9-dihydroxymegastigma-4,6,7-triene (A2)] and four types of glycones [β-d-glucopyranoside (G1), (2-O-β-apiofuranosyl)-β-d-glucopyranoside (G2), (6-O-β-xylopyranosyl)-β-d-glucopyranoside (G3) and (2-O-β-d-apiofuranosyl,6-O-β-d-xylopyranosyl)-β-d-glucopyranoside (G4)]. Aglycones A1 and A2 are known as direct precursors of β-damascenone, and compounds 1–3, which have A1 as an aglycone, have been previously reported from other plant materials. On the other hand, compounds 4–11 are newly characterized as glycosidic progenitors of β-damascenone.