Cardenolide estimation in callus-mediated regenerants of Digitalis lamarckii Ivanina (dwarf foxglove)

Abstract

Digitalis cardenolides can regulate heart rhythms and are effective agents in cancer chemotherapy, in particular, for treating prostate and breast cancer. In this study, an optimized and efficient plant tissue culture protocol was established using callus cultures of Digitalis lamarckii Ivanina, commonly known as dwarf foxglove. Lamina explants developed callus when cultured on Linsmaier and Skoog (LS) medium containing different concentrations of 6-benzyladenine (BA; 4.4, 13.3, or 22.2 μM) and α-naphthalene acetic acid (NAA; 2.7, 5.4, or 10.8 μM). The highest incidence of callus formation (100%) was achieved on LS medium containing 13.3 μM BA and 10.8 μM NAA. Indirect shoot regeneration was achieved when the callus explants were cultured on LS medium supplemented with varying concentrations of BA (0.4, 1.1, or 2.2 μM) and/or gibberellic acid (0.7 or 1.4 μM) for 8 wk. Following the rooting of shoots on LS medium supplemented with either indole-3-acetic acid (ranging from 1.4 to 5.7 μM) or NAA (1.3 to 5.2 μM), lamina and petiole tissues of the 4-mo-old regenerated plants were compared for their cardenolide contents. Lamina extracts showed nearly three times higher cardenolide accumulation than petiole extracts. Of the cardenolides analyzed by reverse-phase high-performance liquid chromatography, neo-odorobioside G and glucogitoroside were abundant in lamina extracts (170.3 and 143.9 mg/kg dry weight, respectively). The regeneration protocol described in this study can be used for the in vitro production of certain cardenolides from D. lamarckii.