Isoquinoline alkaloids from endophytic fungus Aspergillus puniceus and their potential as inhibitors for tobacco powdery mildew

Abstract

The isoquinoline alkaloids have attracted widespread attention from chemists and biologists. With the aims of screening for biological compounds produced by fungi, three new (1-3), together with four known (4-7) isoquinolines were isolated from the cigar tobacco-derived endophytic fungus Aspergillus puniceus in this study. Their structures were determined by means of HRESIMS and NMR spectroscopic studies. Interestingly, the antifungal activity test revealed that compound 5 showed high antifungal activity against G. cichoracearum (DC) (the main pathogen of tobacco powdery mildew disease) with an inhibition rate of 76.3% ± 5.0. Compared to the negative control, compounds 1-4, 6, and 7 also showed notable anti-G. cichoracearum activities with inhibition rates in the range of 38.5-56.9%. The isolation of the above isoquinolines may provide materials for the study of more potent antifungal inhibitors and contribute to an improved utilisation of cigar tobacco-derived endophytic fungi.

Keywords: Aspergillus puniceus; Isoquinolines; alkaloids; antifungal activity.