3,4-Secocycloartane Triterpenoids from the Cones of Pseudolarix amabilis

Abstract Four new 3,4-secocycloartane triterpenoids, pseudolactones A–D (1–4), were isolated from the ethanol extract of the cones of Pseudol arixamabilis. Their structures were established by extensive 1D- and 2D-NMR experiments. The cones of P. arixamabilis are enriched in the ring-expanded or cleaved cycloartane triterpenoids. This work provides new insight into cycloartane triterpenoids from the cones of P. arixamabilis. Graphic Abstract Electronic supplementary material The online version of this article (10.1007/s13659-020-00285-7) contains supplementary material, which is available to authorized users.


3
of them, such as psedolaric acids A and B [10], have shown potent antimicrobial and cytotoxic activities. Peudolarolide B, a triterpene lactone, has shown potent cytotoxic activity [8]. Novel nortriterpenoid lactone, pseudolarenone [11], as well as triterpenoid-diterpenoid dimers [12], have also been reported from the cones of this plant. In this paper, we describe the isolation and structure elucidation of four new 3,4-secocycloartane triterpenoids from the cones of P. amabilis.

Results and Discussion
The dried cones of P. amabilis, collected in Jiujiang, Jiangxi province, P. R. China, were extracted with 80% EtOH for three times at room temperature. The extract was separated by chromatography techniques to yield four new triterpenes, pseudolactones A-D (1-4) (Fig. 1). The structures of four new triterpenoids were determined by analysis of HRESIMS and NMR spectroscopic data.
Compound 1 corresponds to the molecular formula C 32 H 50 O 6 as established by the hydrogen adduct ion peak at m/z 531.3678 [M + H] + (calcd. 531.3680 for C 32 H 51 O 6 + ) in HR-ESI-MS spectrum, indicative of 8 degrees of unsaturation.

General Experimental Procedures
Optical rotations were measured with a Perkin-Elmer 341 polarimeter. IR spectra were recorded with a Bruker Vector-22 Spectrophotometer with KBr discs. NMR spectra were recorded with Bruker DRX-400 spectrometer (400 MHz). The chemical shifts (δ) are given in ppm with TMS as internal standard and coupling constants (J) are given in Hz. MS spectra were recorded with a Agilent MSD-Trap-XCT (for ESI) and Waters Micro-mass Q-TOF mass spectrometer (for HR-ESI-MS), in m/z. Column chromatographic separations were carried out by using silica gel (200-300 mesh; Marine Chemical Factory, Qingdao, P. R. China), Sephadex LH-20 (Pharmacia Fine Chemicals, Piscataway, NJ, USA) as packing material. TLC was carried out on precoated silica gel GF 254 plates (Yantai Chemical Industrials) and the TLC spots were viewed at 254 nm and visualized by using 10% sulfuric acid in alcohol containing 10 mg/mL vanillin.

Plant Material
The