An assay for secologanin in plant tissues based on enzymatic conversion into strictosidine

Abstract

The secoiridoid glucoside secologanin is the terpenoid building block in the biosynthesis of terpenoid indole alkaloids. A method for its determination in plant tissues and in cell suspension cultures has been developed. This assay is based on the condensation of secologanin with tryptamine, yielding strictosidine, in a reaction catalysed by the enzyme strictosidine synthase (STR; E.C. 4.3.3.2). Subsequently, the formation of strictosidine is quantified by high performance liquid chromatography (HPLC). STR was isolated from transgenic Nicotiana tabacum cells expressing a cDNA-derived gene coding for STR from Catharanthus roseus. The high specificity of STR for secologanin, in combination with a sensitive and selective HPLC system, allows a simple extraction of secologanin from plant tissue. The detection limit of this method is 15 ng secologanin. Using this assay, secologanin contents were determined in tissues of various plant species; Lonicera xylosteum hairy roots were found to contain 1% of secologanin on a dry weight basis. # 1998 John Wiley & Sons, Ltd.