Sulochrins and alkaloids from a fennel endophyte Aspergillus sp. FVL2

The fungal endophyte Aspergillus sp. strain FVL2, isolated from the traditional medicinal fennel plant, Foeniculum vulgare, was investigated for secondary metabolites. Fermentation on rice medium followed by chromatographic separation delivered three new natural products, 7-demethyl-neosulochrin ( 1 ), fumigaclavine I ( 3 ) and N-benzoyl-tryptophan ( 6 ) together with further 14 known metabolites, 1-O-methyl-sulochrin-4'-sulfate, questin, laccaic acid, isorhodoptilometrin, fumigaclavine A, fumigaclavine C, fumitremorgin C, fumigaquinazoline C, tryptoquivaline J, trypacidin, 3'-O-demethyl-sulochrin, 1-O-methyl-sulochrin, protocatechuic acid, and vermelone.

The chemical structures of the new metabolites were determined by NMR spectroscopy and ESI HR mass spectrometry. For fumigaclavine I, we observed the partial deuterium transfer from the solvent to the enol form with a remarkable high stereo selectivity. The discovery of the new seco-anthraquinone 7-demethyl-neosulochrin ( 1 ) revealed a second type of ring cleavage by a questin oxygenase.

The discovery of diverse secondary metabolites broadens the chemical space of Aspergillus.