Phytochemical and biological studies on rare and endangered plants endemic to China. Part XV. Structurally diverse diterpenoids and sesquiterpenoids from the vulnerable conifer Pseudotsuga sinensis

摘要

An extensive phytochemical investigation on the chemical constituents from the needles and twigs of the vulnerable conifer Pseudotsuga sinensis yielded 19 diterpenoids and 21 sesquiterpenoids with various carbocyclic skeletons. Among them, 13 (named pseudosinins A-M, resp.) were undescribed compounds. Their structures with absolute configurations were characterized by a combination of spectroscopic methods, calculated and experimental electronic circular dichroism (ECD) data, quantum chemical calculations of the chemical shifts, and single crystal X-ray diffraction analyses. In particular, an array of labdane-derived norditerpenoids with C-19-, C-18-, and C-16-skeletons, and related drimane-type sesquitepenoids with C-15- and C-13-skeletons were found in the title plant. The possible biogenetic relationships of these degraded terpenoids were briefly discussed. Among the isolates, pseudosinin D, cis-communic acid, and 4 beta,15-dihydroxy-19-norabieta-8,11,13-trien-7-one showed moderate inhibitory activities against the enzyme ATP-citrate lyase (ACL), a potential drug target for the treatment of hyperlipidemia and hypercholesterolemia.