Diketopiperazine and enterotoxin analogues from the mangrove derived-soil Streptomyces sp. SCSIO 41400 and their biological evaluation

Abstract

A new diketopiperazine, cyclo-(d-8-acetoxyl-Pro-l-Leu) (1), together with eight known compounds (2–9) including three enterotoxins (2–4), four diketopiperazines (5–8) and maltol (9), were isolated from the mangrove derived-soil Streptomyces sp. SCSIO 41400. The planar structures of all compounds were determined from analysis of NMR spectra, MS, optical rotation and comparing with literature data. The absolute configuration of compound 1 was assigned by electronic circular dichroism (ECD). The isolated compounds (1–9) were tested for their acetyl cholinesterase (AChE) and pancreatic lipase (PL) enzyme inhibitory activities. Among them, the new diketopiperazine (1) displayed preferable PL enzyme inhibitory activity with IC₅₀ value of 27.3 μg/mL, while compounds 2, 5 and 6 showed weak PL enzyme inhibitory activity. Further molecular docking simulation exhibited that compound 1 could be well bind with the catalytic pocket of the PL. Besides, compound 9 showed moderate antibacterial activity against Methicillin-resistant Staphylococcus aureus with MIC value of 12.5 μg/mL, which was comparable to that of the positive control ampicillin with MIC value of 3.125 μg/mL.

Keywords:

• Mangrove derived-soil
• Streptomyces sp.
• diketopiperazine
• enterotoxin
• enzyme inhibitory activities

Acknowledgements

We are grateful to Dr. Zhihui Xiao, Aijun Sun, Xiaohong Zheng, Yun Zhang, and Xuan Ma in the analytical facility at SCSIO for recording spectroscopic data.

Disclosure statement

The authors declare that they have no conflict of interest.

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China (Nos. 41,776,169 and 21,772,210), Special Funds for Promoting Economic Development (Marine Economic Development) of Guangdong Province (No. [2019]A28, [2020]033, [2020]037, [2020]039), and the foundation from Shanxi Educational Committee (15JK1717), National Key Research and Development Program of China (2019YFC0312503), Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0406), Guangdong Local Innovation Team Program (2019BT02Y262).