Alterbutenolide, a new butenolide derivative from a sponge-derived fungus I-YLW6-1.

Alterbutenolide (), a new butenolide derivative with a long-chain aliphatic acid substitution, together with seven known phenolic compounds i.e. alternariol (), asperigillol B (), -hydroxyphenylacetic acid (), -hydroxyphenylethyl alcohol (), methyl -hydroxyphenyl acetate (), 2-(4-hydroxyphenyl)ethyl acetate (), and 5,6-dihydro-4-methyl-2-pyran-2-one (), was isolated from the cultures of a sponge-derived fungus I-YLW6-1. The structure of was established on the basis of HR-MS, 1D and 2D NMR, as well as by comparison of the optical rotation data with the literature reported. Compounds and showed significant to moderate inhibitory activities against three harmful microalgae with IC values from 3.0 to 36.2 μg/mL, whereas compound only displayed moderate inhibition against with IC value of 34.6 μg/mL. Meanwhile, compounds and showed weak toxicity against brine shrimp larvae with LC values >100 μg/mL.