Differential accumulation profiles of hordatine glucosides and aglycons during seedling and seed maturation stages in barley

Hordatines, dehydrodimers of hydroxycinnamoylagmatines, are antifungal compounds that accumulate abundantly in young barley (Hordeum vulgare) seedlings. In addition to the aglycons, several hordatine glucosides have been isolated. However, detailed accumulation profiles of the hordatine glucosides and aglycons remain poorly understood. In this study, we identified the glucosides of hordatines A, B, and C in barley and examined the accumulation profiles of both the glycosides and aglycons during seedling and seed maturation stages. Aglycons accumulated predominantly in shoots, whereas glucosides were the major forms in roots and scutella during seedling stage, and in immature and mature seeds during seed maturation stage. These findings demonstrate that the predominant forms of hordatines vary among tissues and growth stages. The distinct accumulation profiles provide clues for identifying hordatine glucosyltransferase and hordatine glucoside glucosidase, and for elucidating the defensive system involved in the interconversion of hordatine glucosides and aglycons.