Aims: Isolation, identification and characterization of an endophytic fungus from Juniperus communis L. Horstmann, as a novel producer of deoxypodophyllotoxin and its in vitro antimicrobial assay.

Methods and Results: The methodology for the isolation, identification and characterization of a novel endophytic fungus from the twigs of the J. communis L. Horstmann plant, which specifically and consistently produces deoxypodophyllotoxin, was unequivocally established. The fungus was identified as Aspergillus fumigatus Fresenius by molecular, morphological and physiological methods. Deoxypodophyllotoxin was identified and quantified by high‐resolution LC‐MS, LC‐MS² and LC‐MS³. The antimicrobial efficacy of the fungal deoxypodophyllotoxin against a panel of pathogenic bacteria was established.

Conclusions: The production of deoxypodophyllotoxin (found in the host) by the cultured endophyte is an enigmatic observation. It demonstrates the transfer of gene(s) for such accumulation by horizontal means from the host plant to its endophytic counterpart. It would be interesting to further study the deoxypodophyllotoxin production and regulation by the cultured endophyte in J.  communis and in axenic cultures.

Significance and Impact of the Study: This endophyte is a potential handle for scientific and commercial exploitation. Although the current accumulation of deoxypodophyllotoxin by the endophyte is not very high, it could be scaled‐up to provide adequate production to satisfy new drug development and clinical needs. However, further refined precursor‐feeding and mass‐balance studies are required to result in the consistent and dependable production.