New citrinin analogues produced by coculture of the marine algal-derived endophytic fungal strains Aspergillus sydowii EN-534 and Penicillium citrinum EN-535

Abstract

Ten citrinin analogues (1–10), including a new citrinin dimer (seco-penicitrinol A, 2) and a new citrinin monomer (penicitrinol L, 3), were isolated from the EtOAc extracts of the coculture of two marine algal-derived endophytic fungal strains Aspergillus sydowii EN-534 and Penicillium citrinum EN-535. Their structures were elucidated by detailed analysis of their NMR spectra, ECDs, HRESIMS, optical rotation, and X-ray crystallographic data, and by comparison with literature data as well. The crystal structure of compound 1 was reported for the first time in this paper and resulted in unambiguous confirmation of its absolute configuration as 3R, 4S, 2′R, and 3′S, while the absolute configuration of compound 3 was determined by TDDFT calculations of its ECD spectrum. The antimicrobial and influenza neuraminidase inhibitory activities of compounds 1–10 were evaluated.