Indole diketopiperazine alkaloids from the deep-sea-derived fungus Aspergillus sp. FS445

Abstract

Twelve indole diketopiperazine alkaloids (1‒12) including four new ones aspechinulins A‒D (1, 3, 5 and 12) were isolated from the deep-sea-derived fungus Aspergillus sp. FS445. Their structures were elucidated through spectroscopic analysis and the absolute configurations were determined by analyzing the experimental ECD data as well as the quantum chemical calculations. Compounds 1, 3 and 5 represented the first examples of indole diketopiperazine derivatives constructing a C₅ unit at 11-NH through an imide linkage. The NO production inhibitory activity of the isolated compounds was evaluated and compounds 2‒5, 7 and 9 exhibited potential inhibitory activities against NO production with the IC₅₀ values in the range of 20 ∼ 90 µM.

Keywords:

• Indole diketopiperazine
• deep-sea-derived fungus
• quantum chemical calculations
• NO production inhibitory activity

Acknowledgement

We gratefully acknowledge support from the Guangzhou Branch of the Supercomputing Center of Chinese Academy of Sciences, and thank Ai-Jun Sun and Yun Zhang, South China Sea Institute of Oceanology, Chinese Academy of Sciences, for the measurement of HRESIMS.

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

This work was supported financially by the National Natural Science Foundation of China (41906106, 31272087), Guangdong Provincial Special Fund for Marine Economic Development Project (GDNRC [2020]042), the Team Project of the Natural Science Foundation of Guangdong Province (2016A030312014), the GDAS’ Project of Science and Technology Development (2019GDASYL-0103007). National Natural Science Foundation of China (NSFC).