Calcium and magnesium elimination enhances accumulation of cardenolides in callus cultures of endemic Digitalis species of Turkey

Elimination of calcium (Ca), magnesium (Mg) or both from the medium of callus cultures of Digitalis davisiana Heywood, Digitalis lamarckii Ivanina, Digitalis trojana Ivanina and Digitalis cariensis Boiss. ex Jaub. et Spach increased cardenolides production. Callus was induced from hypocotyl segments from one-month old seedlings were cultured on MS medium containing 0.5 μg ml−1 thidiazuron (TDZ) and 0.25 μg ml−1 indole acetic acid (IAA). After 30 days of culture, callus was transferred in hormone-free MS medium (MSO) as well as Ca or Mg or both were completely eliminated from same medium. The amount of five cardenolides from D. davisiana Heywood, D. lamarckii Ivanina, D. trojana Ivanina and D. cariensis Boiss. ex Jaub. et Spach were compared. Higher amounts of five cardenolides and total cardenolides were obtained when callus of four Digitalis species were incubated on MS medium lacking both Ca and Mg. The mean contents of total cardenolides obtained were in the order of D. lamarckii (2017.97 μg g−1) > D. trojana (1385.75 μg g−1) > D. cariensis (1038.65 μg g−1) > D. davisiana (899.86 μg g−1) when both Ca and Mg were eliminated from the medium, respectively. This protocol is useful for development of new strategies for the large-scale production of cardenolides.