Isolierung weiterer Alkaloide ausRauwolfia vomitoria Afz. Vomalidin, ein neues Alkaloid der Ajmalin-Gruppe. 8. Mitteilung überRauwolfia-Alkaloide

Dual Catalytic Activity of a Cytochrome P450 Controls Bifurcation at a Metabolic Branch Point of Alkaloid Biosynthesis in Rauwolfia serpentina

Plants create tremendous chemical diversity from a single biosynthetic intermediate. In plant-derived ajmalan alkaloid pathways, the biosynthetic intermediate vomilenine can be transformed into the anti-arrhythmic compound ajmaline, or alternatively, can isomerize to form perakine, an alkaloid with a structurally distinct scaffold. Here we report the discovery and characterization of vinorine hydroxylase, a cytochrome P450 enzyme that hydroxylates vinorine to form vomilenine, which was found to exist as a mixture of rapidly interconverting epimers. Surprisingly, this cytochrome P450 also catalyzes the non-oxidative isomerization of the ajmaline precursor vomilenine to perakine. This unusual dual catalytic activity of vinorine hydroxylase thereby provides a control mechanism for the bifurcation of these alkaloid pathway branches. This discovery highlights the unusual catalytic functionality that has evolved in plant pathways.

Indole alkaloids from cell suspension cultures of Rauwolfia serpentina benth

Twelve indole alkaloids belonging to the Ajmaline-, Sarpagine-, Yohimbine-, and Heteroyohimbine-type have been isolated and identified from cell suspension cultures of Rauwolfia serpentina. Ten of the alkaloids were found for the first time in cultured R. serpentina cells. The yield of the main alkaloid vomilenine was 51 times more than that of differentiated plants. Crude enzymes isolated from this cell suspension culture completely metabolize the biogenetic precursor strictosidine under formation of several alkaloidal compounds.

3,4-DIHYDRO-β-CARBOLINES: II. THE EXHAUSTIVE METHYLATION OF 3,4-DIHYDRO-β-CARBOLINE

The methiodide of 3,4-dihydro-β-carboline yields a dimeric anhydro base which, on heating, disproportionates to a β-carboline and a tetrahydro-β-carboline derivative, and on methylation is converted to 3-[2-formylindolyl]-β-ethyltrimethylamnionium iodide.