Triggering epipolythiodioxopiperazine alkaloid biosynthesis in fungal endophytes of Goldenseal (Hydrastis Canadensis)

Epipolythiodioxopiperazine (ETP) alkaloids are secondary metabolites that are biosynthesized in fungi and have been reported to have notable cytotoxic and antibacterial activities. ETPs are isolated from a wide variety of fungi, and their biosynthesis does not seem to be linked to certain genera. Preliminary LC-HRESIMS dereplication suggested the presence of ETPs in extracts of two fungal endophytes from goldenseal (Hydrastis canadensis). However, these secondary metabolites were not encountered when regrown, which is a common challenge with fungal endophytes. Therefore, an evaluation of growth conditions to reactivate and maintain the ETP biosynthetic pathway was conducted by adopting the “One Strain-Many Compounds” (OSMAC) approach to culture-based methods. Both endophytes were plated on solid media that varied in nutritional value and in the presence of autoclaved goldenseal and fungal material to trigger the targeted pathway. When these cultures reached full growth on Petri plates, they were subjected to extraction. Then dereplication and mass defect filtering was carried out to identify the presence of potential verticillin analogues under distinct conditions.