Ocellatuspyrones A‒G, new antibacterial polypropionates from the Chinese mollusk Placobranchus ocellatus

Song-Wei Li; Dan-Dan Yu; Ming-Zhi Su; Li-Gong Yao; Hong Wang; Xueting Liu; Yue-Wei Guo

doi:10.1007/s42995-023-00179-w

Ocellatuspyrones A‒G, new antibacterial polypropionates from the Chinese mollusk Placobranchus ocellatus

Mar Life Sci Technol. 2023 Jul 6;5(3):373-386. doi: 10.1007/s42995-023-00179-w. eCollection 2023 Aug.

Authors

Song-Wei Li¹, Dan-Dan Yu², Ming-Zhi Su², Li-Gong Yao³, Hong Wang¹, Xueting Liu⁴, Yue-Wei Guo^{1

3

2}

Affiliations

¹ Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310014 China.
² Shandong Laboratory of Yantai Drug Discovery, Bohai Rim Advanced Research Institute for Drug Discovery, Yantai, 264117 China.
³ State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203 China.
⁴ State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237 China.

Abstract

Marine invertebrates serve as rich sources of secondary metabolites with intriguing chemical diversities and a wide spectrum of biological activities. Particularly, marine shell-less sacoglossan mollusks have attracted much attentions due to the fact that mollusks apply complex metabolites as chemical defense agents against to their predators. With the purpose of discovering bioactive secondary metabolites to develop marine-derived medicines from the South China Sea, we have conducted a chemical study on the photosynthetic mollusk Placobranchus ocellatus. As a result, seven new γ-pyrone polypropionates, namely ( ±)-ocellatuspyrone A (1), ( ±)-ocellatuspyrone B (2), and ocellatuspyrones C-G (5, 9-12), along with five known polypropionates, have been isolated and characterized from the South China Sea photosynthetic mollusk Placobranchus ocellatus. Extensive spectroscopic analysis, single crystal X-ray diffraction analysis, modified Mosher's method, ECD comparison, CD exciton chirality method, TDDFT-ECD calculation, and chemical conversion were used to determine the structures and absolute configurations of the new compounds and the stereochemistry of undefined known compounds 4, 6 and 7. All these isolated polypropionates were evaluated in bioassays for their biological activities, including antibacterial, neuroprotective effect, anti-inflammatory, PTP1B inhibitory, and antiviral activities. Compounds 7, 8 and 11 were found for the first time to show antibacterial activity against fish pathogenic bacteria Streptococcus parauberis (the main pathogen causing fish streptococcal infections and acute death) with MIC values of 35.8, 34.2, and 37.4 μg/mL, respectively, which might be potential novel antibacterial agents for the treatment of fish infectious diseases.

Supplementary information: The online version contains supplementary material available at 10.1007/s42995-023-00179-w.

Keywords: Antibacterial activity; Photosynthetic mollusk; Placobranchus ocellatus; Stereochemistry; γ-pyrone polypropionate.