Biosynthetic Capacity of Stachys Seedlings for Verbascoside and Related Caffeoyl Derivatives

Abstract

Abstract The caffeoyl derivatives of Stachys leaves (Labiateae) were identified as chlorogenic acid, verbascoside and stachyoside. The latter compound, reported here for the fist time, was shown to be a verbascoside derivative containing an extra glucose residue attached to C-2, C-3 or C-4 of rhamnose. Cotyledonary leaves of Stachys accumulate high levels (8 -16 μmol/g dry tissue) of the three caffeoyl derivatives; all of which decrease significantly in amount during plant growth. Intact organs of the seedling were shown to efficiently incorporate the label from different precursors into caffeoyl derivatives. The biosynthesis of both verbascoside and stachyoside from labelled precursors revealed that the caffeoyl moiety was exclusively labelled from phenylalanine or cinnamic acid, whereas the 3,4-dihydroxyphenylethanol moiety was labelled from tyrosine, and better from tyramine.