Ustusaustin A: a new neuraminidase inhibitory meroterpene from the ascidian-derived endophytic fungus Aspergillus ustus TK-5

Abstract

A new austin-type meroterpene, namely, ustusaustin A (1), together with seven related known analogues (2–8), were isolated and identified from the culture extract of Aspergillus ustus TK-5, an endophytic fungus obtained from the marine ascidian Pyura momus. The structures of these compounds were established on the basis of detailed interpretation of their NMR and MS data, and the relative and absolute configurations of 1 was confirmed by X-ray crystallographic analysis. Among them, ustusaustin A (1) represents the first example of 1’-nor-austin analogues with an unique 7-benzoylation. Compounds 1–4, 6, and 7 exhibited potent neuraminidase inhibitory activity and this is the first report of neuraminidase inhibitory activity for austin-type meroterpenes.

Graphical Abstract

Keywords:

• Endophytic fungus
• Aspergillus ustus
• secondary metabolites
• neuraminidase inhibitory activity

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the European Commission under the program ‘Marie Curie Actions-International Research Staff Exchange Scheme’ (IRSES, with Grant Agreement Number PIRSES-GA-2011-295226) and by the National Natural Science Foundation of China-Shandong Joint Fund for Marine Science Research Centers (U1606403). X. Li thanks the China Postdoctoral Science Foundation (Grant No. 2017M612360) and the Shandong Provincial Natural Science Foundation (ZR2017BB073) for the support to the work. B.-G.W. appreciates the support of Taishan Scholar Project from Shandong Province of China.