Jongsomjainuk O.Boonsombat J.Thongnest S.Prawat H.Batsomboon P.Charoensutthivarakul S.Ruchisansakun S.Chainok K.Sirirak J.Mahidol C.Ruchirawat S.Mahidol University2023-12-112023-12-112023-12-01Natural Products and Bioprospecting Vol.13 No.1 (2023)21922195https://repository.li.mahidol.ac.th/handle/123456789/91384Four highly oxidized pimarane diterpenoids were isolated from Kaempferia takensis rhizomes. Kaemtakols A–C possess a tetracyclic ring with either a fused tetrahydropyran or tetrahydrofuran motif. Kaemtakol D has an unusual rearranged A/B ring spiro-bridged pimarane framework with a C-10 spirocyclic junction and an adjacent 1-methyltricyclo[3.2.1.02,7]octene ring. Structural characterization was achieved using spectroscopic analysis, DP4 + and ECD calculations, as well as X-ray crystallography, and their putative biosynthetic pathways have been proposed. Kaemtakol B showed significant potency in inhibiting nitric oxide production with an IC50 value of 0.69 μM. Molecular docking provided some perspectives on the action of kaemtakol B on iNOS protein. Graphical Abstract: [Figure not available: see fulltext.].Biochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1007/s13659-023-00420-02-s2.0-8517819420121922209