Increased cardenolides production by elicitation of Digitalis lanata shoots cultured in temporary immersion systems

Digitalis lanata is an important source of cardenolides such as digoxin and lanatoside C, which have been widely applied in the treatment of cardiac insufficiencies. Elicitation is one of the most effective methods to enhance the biosynthesis of several secondary metabolites in medicinal plants. We studied the effect of elicitation with Chitoplant(A (R)), Silioplant(A (R)) and methyl jasmonate on biomass and cardenolides accumulation in shoots of D. lanata cultivated in temporary immersion systems. Morphological response of the shoots was influenced by elicitors. A reduction in length and number of shoots was evident with all MJ concentrations. Regarding biomass production, Chitoplant(A (R)) (0.1 g l(-1)) was found to impact significantly on fresh and dry weight of the shoots. HPLC analysis revealed a higher content of lanatoside C compared to digoxin in all treatments. The highest accumulation of lanatoside C was achieved with Chitoplant(A (R)) (0.1 g l(-1)), which resulted in 316 mu g g-DW-1 and with Silioplant(A (R)) (0.01 g l(-1); 310 mu g g-DW-1), which accounted for a 2.2-fold increase in lanatoside C content compared to non-elicited shoot cultures. Additionally, elicitation of D. lanata shoots in temporary immersion systems resulted in an oxidative stress characterized by hydrogen peroxide and malondialdehyde accumulation. These observations point to a connection between hydrogen peroxide generation, lipid peroxidation and cardenolide accumulation. The optimization of elicitor treatment and culture conditions for cardenolide production as well as the advantages of TIS for this purpose are discussed.