Interconvertible Pyridone Alkaloids from the Marine-Derived Fungus Penicillium oxalicum QDU1
- J Nat Prod. 2023 Apr 28;86(4):739-750. doi: 10.1021/acs.jnatprod.2c00886.
- 1. Department of Natural Medicinal Chemistry and Pharmacognosy, School of Pharmacy, Qingdao University, Qingdao 266071, China.
- 2. Key Laboratory of Chemical Biology of Ministry of Education, Department of Natural Product Chemistry, School of Pharmaceutical Sciences, Shandong University, Jinan 250100, China.
Eleven new pyridone Alkaloids, penicipyridones A-K (1-11), and three new tetramic acids, tolypocladenols D-F (12-14), were isolated from rice media cultures of the marine-derived fungus Penicillium oxalicum QDU1. Their structures, including absolute configurations, were determined by comprehensive analyses of spectroscopic data, electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction data. Interestingly, several of the penicipyridones undergo interconversions between hydroxy and methoxy groups at C-4 in acidic MeOH solution. Furthermore, in an acidic aqueous solution, OH-4 could be replaced by diverse substituent groups. Compounds 1, 4, 5, 8, 10, 11, and 14 exhibited moderate inhibitory effects on NO production in the LPS-induced RAW264.7 macrophages, with IC50 values ranging from 9.2 to 19 μM.