The biosynthetic relationship between littorine and hyoscyamine in transformed roots of Datura stramonium

The metabolic relationship between littorine and hyoscyamine has been monitored in transformed roots of Datura stramonium. Quantification by GC of unlabelled littorine and by GCMS of ¹³C-labelled littorine demonstrated that exogenously added littorine (0.1 mm) was significantly metabolised (35%) to hyoscyamine. In contrast, exogenously added hyoscyamine was not metabolised to littorine, indicating that this conversion is irreversible. The conversion of littorine to hyoscyamine was suppressed by P-450 oxidase inhibitors (particularly clotrimazole), implicating the involvement, at least in part of a cytochrome P-450 activity operating hyoscyamine biosynthesis. Received: 15 September 1997 / Revision received: 14 February 1998 / Accepted: 10 March 1998