Specific accumulation and revised structures of acridone alkaloid glucosides in the tips of transformed roots of Rutagraveolens

The root tips of Ruta graveolens (common rue) show strong autofluorescence of acridone alkaloids, which are characteristic secondary metabolites of this plant. To study the specific distribution and accumulation of acridone alkaloids in various root segments of Ruta graveolens, root material was harvested from genetically transformed root cultures and extracts were investigated by chromatographic techniques and HPLC-1H NMR spectroscopy. The cells of the elongation and differentiation zones contained acridone glucosides and large amounts of acridone alkaloids, mainly rutacridone. Gravacridondiol glucoside was identified as the dominant secondary compound of the root tips and its structure revised by means of spectroscopic methods. In addition, minor acridones, including the structurally revised gravacridontriol glucoside and unknown natural products, were found in the root tip.

The tissue-specific distribution of acridone alkaloids and glucosides was studied in hairy root cultures of Ruta graveolens by chromatographic and spectroscopic methods including HPLC-NMR. Rutacridone was the major alkaloid in the differentiation zone and gravacridonediol glucoside was the dominant metabolite in the root tips. The structures of two acridone glucosides have been revised.