Eutypoids B−E Produced by a Penicillium sp. Strain from the North Sea

Crude extracts of the Penicillium sp. strain KF620 isolated from the North Sea showed antimicrobial activities against Xanthomonas campestris and Candida glabrata. Purification of the extracts led to the isolation of the new aromatic butenolides eutypoids B (1), C (2), D (3), and E (4). Their structures were elucidated by NMR spectroscopy and supported by HRESIMS and UV data. The antibacterial activity of the crude extracts was due to the presence of the known diketopiperazine fellutanine (cyclo(Trp-Trp)). The eutypoids were neither cytotoxic nor antibacterial, but inhibited the activity of glycogen synthase kinase-3β.