Novel propanamide analogue and antiproliferative diketopiperazines from mangrove Streptomyces sp. Q24

Abstract

A new propanamide analogue (1), along with one known alkaloid (2) and four known diketopiperazines (3–6), was isolated from a cultured broth of the actinomycete Streptomyces sp. Q24 that was obtained from a sample of mangrove soil. The structures of these isolates were characterised as 3-acetylamino-N-2-thienyl-propanamide (1), N-acetyltryptamine (2), cyclo-(l-phenylalanine-l-4-hydroxyproline) (3), cyclo-(l-leucine-l-4-hydroxyproline) (4), cyclo-(l-phenylalanine-d-4-hydroxyproline) (5) and cyclo-(l-leucine-l-proline) (6) based on their NMR and HRESIMS data as well as optical rotation. Three diketopiperazines (3, 4, 6) showed activity in inhibiting the proliferation of human glioma U87-MG and U251 cells. This type of the new propanamide analogue (1) is first found from a nature source and the antiproliferative property of these three diketopiperazines against glioma cells is also reported herein for the first time.

Keywords:

• Mangrove Streptomyces sp
• new propanamide analogue
• diketopiperazines
• glioma cells
• antiproliferative activity

Acknowledgements

Authors greatly appreciate Mrs. Jianyang Pan at Pharmaceutical Informatics Institute of Zhejiang University for performing NMR spectrometry for structure elucidation. We also thank Drs. Zhongjun Ma, Pinmei Wang and Bin Wu at Ocean College of Zhejiang University for donating samples of Staphylococcus aureus, Escherichia coli and Candida albicans. Professor Bi-Run Lin at Institute of Plant Protection of Guangdong Academy of Agricultural Science and Professor Guang-Xiong Zhou at College of Pharmacy of Jinan University were also much appreciated for their help with sample collection.