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A detailed chemical investigation of the secondary metabolites produced by the endophytic fungus Xylaria sp. isolated from the stems of Isodon sculponeatus afforded six new compounds, xylariahgins A–F (1–6), two new natural products (7 and 8), along with two known compounds (9 and 10) (Fig. 1). The structures of all compounds were unambiguously established by analyzing their spectroscopic data or referring to pertinent literature. Compounds 1–8 were tested for their cytotoxic activity against five human tumor cell lines. Electronic supplementary material The online version of this article (10.1007/s13659-018-0158-x) contains supplementary material, which is available to authorized users.

One new 6,7-seco-ent-kaurane diterpenoid, sculponin T (1), was isolated from the aerial parts of Isodon sculponeatus, along with four known analogs, sculponeatin J (2), sculponeatin K (3), sculponeatin C (4), and sculponeatin Q (5). Their structures were elucidated by extensive spectroscopic analysis and by comparison with data reported in the literature. Significant cytotoxic activity was observed for compound 2 against five human tumor cell lines with IC50 values ranging from 1.8 mu mol/L to 3.31 mu mol/L, and it also inhibited NO production in LPS-stimulated RAW264.7 cells, with IC50 value of 3.3 mu mol/L. (C) 2014 Jian-Xin Pu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Phytochemical investigation of the aerial parts of Isodon sculponeatus afforded six new 7,20-epoxy-ent-kauranoids, sculponins U-Z (1-6), and 11 known diterpenoids (7-17). The structures of these new compounds were elucidated primarily by means of extensive spectroscopic analysis, and the absolute configuration of 1 was determined by single crystal X-ray diffraction. Compound 5 exhibited weak cytotoxic activity against HL-60, SMMC-7721, MCF-7, and SW-480 cell lines, and it also inhibited NO production in LPS-stimulated RAW264.7 cells, with IC50 value of 13.8 μM.

Fourteen enmein-type 6,7-seco-ent-kaurane diterpenoids, seven new ones (sculponins M-S, 1-7) and seven known compounds (8-14), were isolated from the aerial parts of Isodon sculponeatus. Compound 1 is the first example of an ent-kauranoid, possessing a 11,12-epoxy group, and compounds 6 and 7 have a rare 3,6-epoxy group. The structures were established primarily by NMR and MS methods, and the absolute configurations of 1, 3, and 6 were determined by single-crystal X-ray diffraction. Compound 14 showed significant cytotoxic activity against five human tumor lines, with IC50 values ranging from 1.0 to 3.5 mu M, and it also inhibited NO production in LPS-stimulated RAW264.7 cells, with an IC50 value of 2.2 mu M.

Six new 6,7-seco-ent-kaurane diterpenoids, sculponeatins N-S (1-6, resp.), together with eleven known analogues, 7-17, were isolated from the aerial parts of Isodon sculponeatus. The structures of compounds 1-6 were elucidated by spectroscopic methods including extensive ID- and 2D-NMR experiments, as well as HR-ESI-MS analysis. All diterpenoids obtained were assayed for their cytotoxic activity against K562 and HepG2 human tumor cell lines. Among them, compound 1 showed the most significant cytotoxicity with the IC(50) values of 0.21 and 0.29 mu M, respectively. The structure-activity relationships are discussed.

Further investigation on the leaves of Isodon sculponeatus afforded two new ent-kaurane diterpenoids, sculponeatins J and K. Their structures were elucidated on the basis of their spectral properties, as well as X-ray crystallographic analysis. The cytotoxicities of these two new compounds against human tumor cells K562 and T24 were also tested, and sculponeatin J showed significant inhibitory effects with IC50 values less than 1.0 μg/mL.

Three new 6,7-seco-eni-kauranoids (1-3) were isolated and structures were elucidated from Isodon sculponeatus. Diterpenoids 1-3 possessing multicyclic skeletons formed via oxygen atoms are all unprecedented among ent-kauranes. Compound I displayed significant cytotoxic activity against K562, A549, and HepG2 human tumor cell lines, with IC50 values of 1.4, 2.3, and 2.0 mu M, respectively, equal to the positive control. Plausible pathways for the biosynthesis of I and 2 from one related diterpenoid were also postulated. (C) 2007 Elsevier Ltd. All rights reserved.

Sculponin T (I) is isolated from the aerial parts of Isodon sculpneatus along with four known analogs.

Nine new ent-kauranoids, sculponins D-L (1-9), and 14 known diterpenoids (10-23) were isolated from the aerial parts of Isodon sculponeatus. The structures of the new diterpenoids were determined by detailed interpretation of their 1D and 2D NMR spectra and HRESIMS. The isolated compounds were evaluated for their cytotoxic activities against a small panel of human cancer cell lines.