The Metabolites Produced by Citrus reticulata ‐Derived Endophyte Aspergillus fumigatus as Potential Antifungal Agents Against Citrus Pathogens

ABSTRACT

Six new bergamotene sesquiterpenoids ( 1 – 6 ), one new cyclohexenone derivative ( 7 ), and nine known compounds ( 8 – 16 ) were isolated from Citrus reticulata ‐associated endophytic fungus Aspergillus fumigatus . The structures were systematically established mainly by NMR data, HRESIMS, DP4+ analysis, and ECD calculations. Compounds 2 – 6 were proposed to be derived from β‐ trans ‐bergamotene via C‐5/C‐6 skeletal cleavage and further modifications. Among them, compounds 2 and 3 represent the first reported instances of the β‐bergamotene derivatives bearing an epoxide moiety, characterized by unique 6/5/3 and 6/6/3 tricyclic frameworks based on oxabicyclo[3.2.1]octane and oxabicyclo[3.3.1]nonane cores, respectively. Antifungal activities against two citrus pathogens, Fusarium graminearum and Alternaria alternata , revealed that most compounds exhibited significant antifungal activities, with MIC values of 1–8 µg/mL. Notably, the antifungal activities of compounds 8 and 9 against A. alternata and compound 14 against F. graminearum were comparable to those of nystatin.