Investigation of Secondary Metabolites from Marine‐Derived FungiAspergillus

Abstract Marine fungi Aspergillus flavipes and A. terreus were investigated for secondary metabolites using electrospray ionization‐quadrupole time‐of‐flight mass spectrometry (ESI‐QTOF MS) analysis. The ESI‐MS analysis showed that A. flavipes showed molecular ion peaks for compounds, terrein (1) , butyrolactone I (2) , butyrolactone I‐carboxylic acid (3) , butyrolactone III (4) , while, A. terreus had additional presence of new compound aspernolide Q (5) with absence of compound (3) . By using tandem mass spectrometry data, the prominent fragment ions helped in the establishing the structure of compounds (2‐5) . Further, chemical transformation of butyrolactone I to butyrolactone III and aspernolide Q were carried out followed by NMR analysis which strongly suggested their structures. The evaluation of salt stress experiment of A. terreus culture medium affected the production of major bioactive metabolites, terrein and butyrolactone I (2) . The HPLC analysis showed that culture produces high amount of terrein at 35 ‰, while, maximum production of butyrolactone I was observed in fresh water i. e. 0‰. The study highlighted an importance of salinity in producing these metabolites where, terrein and butyrolactone I could be produced in equal ratio at 18‰. Importantly, we have demonstrated that using this fungal strain and by growing in medium at specific salinity could be way forward for commercial production of these bioactive compounds.