Di- and Triterpenoids from the Rhizomes of Isodon amethystoides and Their Anti-inflammatory Activities
- J Nat Prod. 2023 May 26;86(5):1230-1239. doi: 10.1021/acs.jnatprod.2c01136.
- 1. State Key Laboratory of Quality Research in Chinese Medicine, Guangdong-Hong Kong-Macao Joint Laboratory of Respiratory Infectious Disease, Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Macau 999078, People's Republic of China.
- 2. School of Pharmaceutical Sciences, Shandong University of Traditional Chinese Medicine, Jinan 250355, People's Republic of China.
Amethystoidesic acid (1), a triterpenoid with an unprecedented 5/6/6/6 tetracyclic skeleton, and six undescribed Diterpenoids, amethystoidins A-F (2-7), were isolated from the rhizomes of Isodon amethystoides along with 31 known di- and triterpenoids (8-38). Their structures were fully elucidated via extensive spectroscopic analysis including 1D and 2D NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), and electronic circular dichroism (ECD) calculations. Compound 1 is the first example of a triterpenoid possessing a rare ring system (5/6/6/6) derived from a contracted A-ring and the 18,19-seco-E-ring of ursolic acid. Compounds 6, 16, 21, 22, 24, and 27 significantly inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, which could be partly mediated by the downregulation of LPS-induced inducible nitric oxide synthase (iNOS) protein expression.