Biosynthesis of the iridoid glucoside, lamalbid, in Lamium barbatum.

The biosynthesis of the iridoid glucoside lamalbid in Lamium barbatum, a plant species in the Lamiaceae, was investigated by administrating (13)C-labeled intermediates of MVA and MEP pathways, respectively. The results demonstrated that [3,4,5-(13)C(3)]1-deoxy-D-xylulose 5-phosphate could be incorporated into lamalbid, whereas the incorporation of [2-(13)C(1)]mevalonolactone was not observed. Based on the (13)C labeling pattern of lamalbid and the incorporation data, we deduce that the iridoid glucoside in L. barbatum is biosynthesized through the MEP pathway, whereas the classic MVA pathway is not utilized.