Isolation, Structure Elucidation, and Absolute Configuration of Highly Oxygenated Germacranolides from Carpesium cernuum

New 11-Methoxymethylgermacranolides from the Whole Plant of Carpesium divaricatum

Eight new 11-methoxymethylgermacranolides (1–8) were isolated from the ethanol extract of the whole plant of Carpesium divaricatum. The planar structures and relative configurations of the new compounds were determined by detailed spectroscopic analysis. The absolute configuration of 1 was established by electronic circular dichroism (ECD) spectrum and X-ray crystallographic analysis, and the stereochemistry of the new compounds 2–8 were determined by similar ECD data with 1. The absolute configurations of 5 and 7 were further confirmed by using quantum chemical electronic circular dichroism (ECD) calculations. Compound 4 exhibited weak cytotoxicity against MCF-7 cells. Compound 8 could potently decrease PGE2 productions in LPS-induced RAW 264.7 cells.

Chemical constituents of plants from the genus Carpesium

Carpesium (Family – Compositae) is a genus with 24 species of mainly perennial herbs. Several species of this genus have served as folk medicine in China and Korea for their antipyretic, anti-inflammatory, analgesic, antifungal, antibacterial, and cytotoxic activity properties. Chemical constituents are mostly sesquiterpenes, diterpenes, glycosides, and several other types of compounds. This article summarizes the literature on the isolated and identified constituents from various Carpesium species and their various biological activities.

Vlasouliodes A-D, four new C30 dimeric sesquiterpenes exhibiting potential inhibition of MCF-7 cells from Vladimiria souliei

As our ongoing interest to search bioactive dimeric sesquiterpenes from the genus Vladimiria (Asteraceae), the plant of Vladimiria souliei was studied. Based on the repetitive chromatographic fractionation, a chemical investigation on the roots of Vladimiria souliei led to the isolation and the identification of four previously undescribed sesquiterpene dimers, vlasouliodes A-D (1-4). Their chemical structures were elucidated by comprehensive analysis of spectroscopic data, including HRESIMS, 1D and 2D NMR spectroscopic data. The absolute configurations of them were unambiguously established by the experimental and calculated ECD data. In the in vitro biological activity evaluation, 1 and 3 displayed pronounced inhibitory activity against human breast adenocarcinoma cell lines (MCF-7) with IC₅₀ values of 17.12 ± 0.42 μM and 13.12 ± 0.10 μM, respectively. Additionally, treatment with 1 and 3 induced cell apoptosis in MCF-7 cells, down-regulated the expression of Caspase-3 and up-regulated the expression of Cleaved-caspase-3.

A new highly oxygenated germacranolide from Carpesium nepalense var. lanatum (C.B.Clarke) Kitam

A new highly oxygenated germacranolide, carcerlane A (1), together with four known highly oxygenated germacranolides (2-5), was isolated from an ethanol extract of the whole plant of Carpesium nepalense var. lanatum (C.B.Clarke) Kitam. The structures were determined by HRESIMS and extensive analysis of their spectroscopic data including IR, 1 D and 2 D NMR spectra. To our best knowledge, it was the first time to report the phytochemical investigation on this plant. The anti-Alzheimer's disease (AD) activities of 1-5 were evaluated using Caenorhabditis elegans AD pathological model. All the tested compounds showed that they have the anti-AD bioactivities of delaying worms paralysis.

Germacranolide sesquiterpenes from Carpesium cernuum and their anti-leukemia activity

In this study, three new germacranolide sesquiterpenes (1-3), together with six related known analogues (4-9) were isolated from the whole plant of Carpesium cernuum. Their structures were established by a combination of extensive NMR spectroscopic analysis, HR-ESIMS data, and ECD calculations. The anti-leukemia activities of all compounds towards three cell lines (HEL, KG-1a, and K562) were evaluated in vitro. Compounds 1-3 exhibited moderate cytotoxicity with IC₅₀ values ranging from 1.59 to 5.47 μmol·L^-1. Mechanistic studies indicated that 2 induced apoptosis by decreasing anti-apoptotic protein Bcl-2 and activating the caspase family in K562 cells. These results suggest that compound 2 is a potential anti-leukemia agent.

Antiprostate Cancer Activity of Ineupatolide Isolated from Carpesium cernuum L

Objective

The aim of the study was to investigate the antiprostate cancer effects and mechanism of ineupatolide (T-21), a natural product isolated from the Compositae plant Carpesium cernuum L., on PC-3 human prostate cancer cells.

Methods

The effect of T-21 on the proliferation of PC-3 cells was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, cell migration, and invasion experiments; the morphology of cell apoptosis was observed by Hoechst-propidium iodide staining; the effects of T-21 on PC-3 cell apoptosis and the cell cycle were evaluated by flow cytometry; and the effect of T-21 on the expression levels of phosphorylated protein kinase B (p-AKT), AKT, X-linked inhibitor of apoptosis protein (xlAP), procaspase-3, and poly (ADP-ribose) polymerase (PARP) in PC-3 cells was measured by western blotting.

Results

T-21 significantly inhibited the proliferation of cells, and its half-maximal inhibitory concentrations at 12, 24, and 48 h were 38.46 ± 1.01, 24.63 ± 0.70, and 7.36 ± 0.58 μM, respectively. T-21 may promote cell apoptosis in a concentration-dependent manner and block the cell cycle in the G2 and S phases. In addition, T-21 significantly reduced the protein expression levels of p-AKT, AKT, xlAP, procaspase-3, and PARP.

Conclusion

T-21 exhibits antiproliferation effects on PC-3 cells by promoting apoptosis and arresting the cell cycle in the G2 and S phases. The possible mechanism underlying its potential therapeutic effects against prostate cancer is related to the AKT/xlAP pathway.

Composition of Essential Oils from Roots and Aerial Parts of Carpesium cernuum and Their Antibacterial and Cytotoxic Activities

Carpesium cernuum L., one of the two Carpesium species occurring in Europe, in the Far East and India, found use as a vegetable and a traditional medicinal remedy for several ailments. In the present study, compositions of essential oils distilled from roots and shoots of C. cernuum plants, cultivated in the open field, have been studied by GC-MS-FID supported by NMR spectroscopy. The analyses led to the identification of 120 compounds in total, of which 115 were found in aerial parts and 37 in roots of the plants. The major constituents found in the oil from shoots were: α-pinene (35%) and 2,5-dimethoxy-p-cymene (thymohydroquinone dimethyl ether, 12%), whereas 2,5-dimethoxy-p-cymene (55%), thymyl isobutyrate (9%) and thymol methyl ether (8%) predominated in the essential oil obtained from the roots. Antibacterial and cytotoxic activities of the essential oils distilled from C. cernuum were also tested. The essential oil from aerial parts of the plant demonstrated good inhibitory activity against Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 (MIC: 15.6 μL/mL).

Cytotoxic Germacranolides from the Whole Plant of Carpesium minus

Eight new germacranolides, minusolides A-H (1-8), along with two known analogues, 9 and 10, were isolated from the whole plant of Carpesium minus. Their structures were elucidated by spectroscopic analysis. Compounds 1 and 2, and 6 and 9 are two pairs of rare epimers with opposite configurations at C-2 of the 2-methylbutyryloxy group. The absolute configurations were determined by X-ray diffraction studies. Compound 7 exhibited cytotoxic activities against MDA-MB-231, A549, and HCT-116 cells with IC₅₀ values of 6.1 ± 0.2, 8.4 ± 0.6, and 3.7 ± 0.6 μM, respectively. Compound 7 induced the apoptosis of HCT-116 cells via suppression of PARP and promoting cleavage of PARP.

xOPBE: A Specialized Functional for Accurate Prediction of 13C Chemical Shifts

In this study, we present a new hybrid functional denoted as xOPBE, which is optimized at the 6-311+G(2d,p) basis set and designed with a specific aim of providing accurate ¹³C chemical shifts. By mixing the Hartree-Fock exchange into the OPBE functional, xOPBE provides a significantly improved overall performance as compared to its parent OPBE functional, while OPBE was shown previously as an excellent functional for ¹³C chemical shifts. Even in the case of the 1-adamantyl cation, for which OPBE completely fails in reproducing the experimental results, xOPBE still performs very well with similar accuracy as the standard CCSD(T) method with a large basis set. Our results also demonstrate that xOPBE not only can improve quantitatively the description of the correct assignments given by OPBE but also can revert OPBE's incorrect assignments qualitatively. Thus, we would like to recommend the use of xOPBE for routine evaluations of ¹³C chemical shifts.

Identification of Carpesium cernuum extract as a tumor migration inhibitor based on its biological response profiling in breast cancer cells

BACKGROUND

Breast cancer is one of the most lethal cancers in women when it reaches the metastatic stage. The plant Carpesium cernuum has been used as an anti-inflammatory, analgesic, and detoxifying agent in Chinese folk medicine. However, the inhibitory activity and molecular mechanisms of Carpesium cernuum in breast cancer cells have not been investigated.

METHODS

RNA sequencing experiments were performed to elucidate the cellular pathways affected by Carpesium cernuum extract (CCE). Cell viability and EdU incorporation assays were conducted to determine the effect of CCE on cell proliferation. The inhibitory effects of CCE on the expression levels of target genes were confirmed by qRT-PCR and Western blot. Cell migration and invasion were analysed with transwell chamber assays.

RESULTS

Proliferation assays indicated that CCE inhibited cell proliferation in multiple cancer cell lines and the IC₅₀ value of CCE was the smallest in MDA-MB-231 cells. Transcriptome analysis showed that CCE significantly affected the cell adhesion pathway. Further experiments revealed that CCE suppressed cell migration and invasion. The inhibitory effect on migration was likely mediated by targeting TIMP1, MMP9, CD44 and COL4A2. The main active components of CCE were isolated, and CCE-derived sesquiterpene lactone substances could reproduce the inhibitory effect of CCE on cell migration and invasion.

CONCLUSIONS

Overall, both molecular and phenotypic assays showed that CCE has potential in the treatment of breast cancer, especially for the treatment of breast cancer metastasis. CCE-derived sesquiterpene lactone substances are the foundation for the tumor inhibitory effect of CCE.

Cytotoxic Germacrane-Type Sesquiterpene Lactones from the Whole Plant of Carpesium lipskyi

Ten new sesquiterpene lactones, carlipsines A-J (1-10), and 12 known analogues (11-22) were isolated from the whole plant of Carpesium lipskyi. Their structures were elucidated by using 1D and 2D NMR and HRESIMS analyses, and their absolute configurations were confirmed by X-ray diffraction studies. All compounds were identified as germacranolides with diverse substructural features. Compounds 1-4 are 2,5-hemiacetal-linked germacranolides. Compounds 5 and 6 possess a 1,2-epoxy moiety. Compounds 7 and 8 represent unusual 1,5-hemiacetal-linked germacranolides. Compounds 9 and 10 contain a tetrahydrofuran unit with the oxygen atom bridging C-1 and C-8. Compounds 6, 7, 8, 19, 20, 21, and 22 showed cytotoxicity against HL-60 and A-549 cell lines with IC₅₀ values ranging from 2.8 to 10.3 μM.

New antiproliferative germacranolides from Carpesium divaricatum

Six new highly oxygenated (2–7) and one known (1) germacranolides were isolated from the whole plant of Carpesium divaricatum. The planar structures and relative configurations of the new compounds were determined by detailed spectroscopic analysis. The absolute configurations of 1 and 3 were established by circular dichroism (CD) and X-ray crystallographic analyses, and the stereochemistry of the new compounds 2 and 4–6 were determined by similar CD data to 1 and 3, respectively. All isolates were evaluated for their antiproliferative activities against three human tumor cell lines, and compounds 3 and 6 show antiproliferative activities against HeLa and Hep G2 cells with IC₅₀ values of 4.13–8.37 μM. Intensive mechanism study showed that 3 caused cell-cycle arrest at the S/G2 phase and induced apoptosis in Hep G2 cells through a mitochondria-related pathway.

A new compound from Carpesium divaricatum has the potential to treat liver cancer through apoptosis induction and cell cycle arrest.

Isolation, Structure Elucidation, and Absolute Configuration of Germacrane Isomers from Carpesium divaricatum

Five sets of germacrane isomers (1/8/17, 2/7/10/11/13/16/18, 3/4/5/14/20, 6/12/15, and 9/19) with different skeletal types, including seven new ones (1-3, 8-9, and 15-16) were isolated from the whole plant of Carpesium divaricatum. Among them, there are six pairs of stereoisomers (1/8, 2/13, 4/14, 6/12, 7/11 and 10/11). The planar structures and relative configurations of the new compounds were elucidated by detailed spectroscopic analysis. The absolute configurations of 4, 10, 11, and 17 were established by circular dichroism (CD) spectra and X-ray crystallographic analyses, and the stereochemistry of the new compounds 1-3, 8-9, and 15-16 were determined by similar CD spectra with 4, 10, 11, and 17, respectively. The confusion in the literature about subtypes I and II of germacranolides was clarified in this paper. The NMR data of 10-11, and the absolute configurations of the known compounds 4-6, 13-14, and 17-20 were reported for the first time. Compounds 13, 17, and 18 showed cytotoxicity against human cervical (HeLa), colon (LoVo) and stomach cancer (BGC-823) cell lines with IC₅₀ values in the range 4.72-13.68 μM compared with the control cis-platin (7.90-15.34 μM).

Natural Products Research in China From 2015 to 2016

This review covers the literature published by chemists from China during the 2015-2016 on natural products (NPs), with 1,985 citations referring to 6,944 new compounds isolated from marine or terrestrial microorganisms, plants, and animals. The emphasis is on 730 new compounds with a novel skeleton or/and significant bioactivity, together with their source organism and country of origin.

Survey of natural products reported by Asian research groups in 2016

The new natural products reported in peer-reviewed articles in 2016 in journals with good reputations were reviewed and analyzed. The advances that Asian research groups made in the field of natural products chemistry in 2016 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on structural classification.