Two new terrein derivatives, aspergilethers A and B (1 and 2), two known analogues (3 and 4), and three known butenolides (5-7) were isolated from the endophyte Aspergillus terreus HT5. Their structures were determined by spectroscopic analysis and ECD and NMR calculations. Interestingly, 1 and 2 had unpresented medium aliphatic side chains in terrein derivatives, with different absolute configurations at C-7, which was very scarce. (+)-Terrein (3) exhibited potent postemergence phytotoxicity toward Amaranthaceae, Portulacaceae, and Fabaceae, with MIC values of 250-1000 μg/mL. Transcriptome analysis and qRT-PCR suggested that (+)-terrein induced the transcriptional expression of aging-related genes to accelerate organ senescence and stimulated plant detoxification response. The conjugated system between keto carbonyl and double bonds in the cyclopentenone ring and side chain, and the configurations of C-2 and C-3, played critical roles in the phytotoxicity of terrein derivatives. Meanwhile, 3 was first reported to display moderate antioomycetes activity toward Phytophthora nicotiana.
Keywords: antioomycetes; butenolides; phytotoxicity; terrein derivatives; transcriptome.