Prospecting endophytic fungal assemblage of Digitalis lanata Ehrh. (foxglove) as a novel source of digoxin: a cardiac glycoside

Endophytes, the chemical synthesizers inside plants, are the microorganisms having mutualistic relationship with the host plant. They can be used by plants for defense in addition to the production of a wide variety of beneficial bioactive secondary metabolites. There are reports that microbial endophytes mimic the bioactive compounds as produced by the plant itself thus making them a promising source of novel compounds. During the present study, endophytes were isolated from the symptomless leaves and stem of the angiosperm, Digitalis lanata (foxglove). Digitalis lanata belongs to the family Plantaginaceae and is an important medicinal plant known for the production of an important glycoside, digoxin having valuable medicinal importance. Glycosides from Digitalis have been reported to be cardiotonic and are widely used in the treatment of various heart conditions namely atrial fibrillation, atrial flutter, heart failure, etc. Endophytic fungi were isolated from Digitalis to screen them for such glycosides as have been found in the plant itself. A total of 35 fungal endophytes were isolated and screened for the production of secondary metabolites. After preliminary analysis by thin layer chromatography for the presence of bioactive compounds, crude extracts of five fungal cultures were selected for HPLC. HPLC chromatograms revealed the production of glycoside digoxin from the five selected endophytic cultures, thus providing a novel, alternative and eco-friendly source for the production of such a pharmaceutically important and valuable drug.