Secondary metabolites in hairy root cultures of Leontopodium alpinum Cass. (Edelweiss)

Abstract

The formation of 5 hairy root lines of Leontopodium alpinum was induced by infection of sterile plants with Agrobacterium rhizogenes. The transformed roots were grown as batch cultures in a phytohormone-free modified Murashige & Skoog medium. A time-course experiment with the most productive line showed that a culture period of 6 weeks was optimum for biomass production yielding a 70-fold increase in fresh weight. A 70% enhancement of anthocyanin formation could be induced by addition of benzyladenine (to a final concentration of 0.5 mg l^-1) to the culture medium 14 days before harvest. The presence in the cultures of chlorogenic acid as well as other hydroxycinnamic acid esters was confirmed by TLC. An essential oil (ca. 0.6%) was separated from the hairy roots by steam distillation, a high variability in oil yield being observed between the different lines. GC analyses showed the oils to be complex mixtures of > 30 compounds, with 2 of these consistently representing ca. 60% of the oils. The essential oils isolated from hairy roots were found to be qualitatively similar to the natural root oil, although quantitative differences in oil components were apparent. Oil yields could be increased by growing roots in the absence of light.