Dicarabrones A and B, a pair of new epimers dimerized from sesquiterpene lactones via a [3 + 2] cycloaddition from Carpesium abrotanoides

MS/MS-based molecular networking discovery of sesquiterpenes from Carpesium abrotanoides L. with their cytotoxic and acetylcholinesterase inhibitory activity

Employing an MS/MS-based molecular networking-guided strategy, three new eudesmane-type sesquiterpenes (1-3) and one undescribed pseudoguaianolide sesquiterpene (8), along with four known eudesmane-type sesquiterpene lactones (4-7) were extracted and purified from the herbs of Carpesium abrotanoides L. Structural elucidation encompassed comprehensive spectroscopic analysis, NMR calculations, DP4+ analysis, and ECD calculations. The cytotoxicity activity of all isolates was evaluated against two human hepatoma carcinoma cells (HepG2 and Hep3B) in vitro. It was demonstrated that compounds 2 and 4 showed moderate cytotoxic against HepG2 and Hep3B cells. Furthermore, all compounds were evaluated for their acetylcholinesterase (AChE) inhibitory activity. Particularly noteworthy is that, in comparison to the positive control, compound 1 demonstrated significant AChE inhibition with an inhibition rate of 77.86%. In addition, the inhibitory mechanism of compound 1 were investigated by in silico docking analyze and molecular dynamic simulation.

Aspercitrininone A, novel antibacterial polyketide featuring unusual spiral skeleton from Aspergillus cristatus

Aspercitrininone A (1), a novel polyketide featuring an unprecedented tetracyclic 6/6/6/5 spiral skeleton, was obtained from the rice fermentation cultures of the fungus Aspergillus cristatus together with five known compounds (2-6). Their structures were determined by HRESIMS data, 1D and 2D NMR spectroscopic analysis, and electronic circular dichroism (ECD) calculations. Aspercitrininone A was revealed as a new type of C/D cycle spiral structure and an unusual addition product of o-quinoid form citrinin with 2-methylterrefuranone. Compounds 1, 4, and 5 exhibited potent antibacterial activities with minimal inhibitory concentration (MIC) values from 13.2 to 67.3 μg/mL against four strains of human pathogenic bacteria in vitro.

Hysterolides A-I, dimeric or monomeric sesquiterpene lactones from Parthenium hysterophorus L

Nine undescribed sesquiterpene lactones, including two pseudoguaianolide dimers (1 and 2), a pseudoguaiac dilactone (3), and six pseudoguaianolides (4-9), along with 13 known analogues (10-22) were isolated from Parthenium hysterophorus. Among them, hysterolide A (1) possesses an unusual carbon skeleton with a unique cyclobutane ring connecting two pseudoguaianolides. Hysterolide C (3) is a sesquiterpene dilactone incorporating a bicyclo[5.1.0]octane core. Spectroscopic analyses, 13C NMR and ECD calculations, and X-ray diffraction elucidated their structures and absolute configurations. Moreover, all the isolates were assayed for their anti-inflammatory activities by inhibiting LPS-induced nitric oxide production in BV-2 microglia cells, wherein, nine compounds displayed significant inhibitory activities with IC50 of 0.52-6.32 μM. Furthermore, the preliminary structure-activity relationship was also established.

Sesquiterpene lactone dimers from the fruit of Carpesium abrotanoides L

Seven undescribed sesquiterpene lactone dimers (SLDs) (carpeabrodilactones A-G), one known SLD, and six known sesquiterpenes were isolated from the fruit of Carpesium abrotanoides L. Carpeabrodilactone A was a dimeric carabrane featuring a rare C-13-C-13' linkage. Carpeabrodilactones B and C are the first two SLDs to be described possessing a carabranolide unit and a guaianolide unit connected by an O-ether linkage. The structures of the SLDs were assigned based on HRESIMS, NMR analysis, ¹³C NMR calculation, ECD calculation, and modified Mosher's method. Four SLDs showed potent cytotoxicity against K562 and/or A549 cells, with IC₅₀ values below 10 μM, but none inhibited protein tyrosine phosphatases at 40 μM, including PTP1B, SHP1, CD45, and TCPTP.

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.

Ethnobotanical Uses, Phytochemical Composition, Biosynthesis, and Pharmacological Activities of Carpesium abrotanoides L. (Asteraceae)

Carpesium abrotanoides L. (Asteraceae) is a medicinal plant with immense therapeutic importance and bioactivities. It is commonly encountered in various Asian regions. It has numerous ethnomedicinal uses for curing diverse ailments such as toothache, stomach ulcer, boils, tonsillitis, bronchitis, bacterial infection, bruises, swelling, virus infection, fever, and amygdalitis, as well as an anthelmintic versus round-, tape-, hook-, and pinworms. Different classes of phytoconstituents such as sesquiterpenes, sesquiterpene dimers, monoterpenes, and nitrogenous compounds have been reported from this plant. These phytoconstituents have proved to possess anti-inflammatory, cytotoxic, antimicrobial, and insecticidal capacities. The present review aims to summarize all published data on C. abrotanoides including traditional uses, phytoconstituents, bioactivities, and toxicological aspects, as well as the synthesis and biosynthesis of its metabolites through an extensive survey on various databases and various publishers. These reported data could draw the attention of various natural-metabolite-interested researchers and medicinal chemists towards the development of this plant and/or its metabolites into medicine for the prevention and treatment of certain illnesses. Despite the diverse traditional uses of C. abrotanoides, there is a need for scientific evidence to support these claims. Clinical trials are also required to further assure these data and validate this plant utilization in treating several diseases.

Three new carabrane sesquiterpenoid derivatives from the whole plant of Carpesium abrotanoides L

Dicarabrols B and C (1 and 2), two new carabrane sesquiterpenoid dimers, along with one new carabrane sesquiterpenoid (3) were isolated from the whole plant of Carpesium abrotanoides L. Their full structures were established by extensive analysis of HR-ESI-MS and NMR spectroscopic data, and time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. Dicarabrol B possesses a novel C₃₀ skeleton featuring a methylene-tethered bridge between two sesquiterpene moieties, while dicarabrol C presents the unique linkage of a cyclopentane ring in the molecule. Dicarabrol C exhibited potent inhibitory effects on HL-60 cells with an IC₅₀ value of 3.7 μmol·L^-1.

Targeted isolation of two disesquiterpenoid macrocephadiolides A and B from Ainsliaea macrocephala using a molecular networking-based dereplication strategy

Two novel dimeric sesquiterpenoids with potent anti-inflammatory activity were characterized from Ainsliaea macrocephala through a molecular networking-based dereplication strategy.

Tricarabrols A–C, three anti-inflammatory sesquiterpene lactone trimers featuring a methylene-tethered linkage from Carpesium faberi

Three anti-inflammatory trimeric compounds constructed from carabrol-type sesquiterpenoids through a methylene-tethered linkage were characterized from Carpesium faberi.

Natural disesquiterpenoids: an update

This review highlights the progress on the isolation, bioactivity, biogenesis and total synthesis of dimeric sesquiterpenoids since 2010.

Fused multicyclic polyketides with a two-spiro-carbon skeleton from mangrove-derived endophytic fungus Epicoccum nigrum SCNU-F0002

A pair of uncommon fused multicyclic polyketides, (±)-isoepicolactone and one new isobenzofuranone monomer, together with four other known biosynthetically related compounds were isolated from the fermentation of fungus Epicoccum nigrum SCNU-F0002.

Artemisianins A-D, new stereoisomers of seco-guaianolide involved heterodimeric [4+2] adducts from Artemisia argyi induce apoptosis via enhancement of endoplasmic reticulum stress

Artemisianins A-D (1-4), four stereoisomers of sesquiterpenoid dimers, forming via [4+2] cycloaddition from a 1, 10-seco-guaianolide dienophile and a guaianolide diene, along with two biosynthetically related precurors 5 and 6, were isolated from the famous traditional Chinese medicine Artemisia argyi. The structures of 1-4, including their absolute configurations, were elucidated by extensive spectroscopic data and ECD/TDDFT calculation analysis. Compounds 1-4 exhibited cytotoxicity with IC₅₀ values ranging from 7.2 to 23.3 μM. The accumulation of Ca²⁺ in cytoplasm and enlarged endoplasmic reticulum (ER) indicated that 1 mediated HT-29 cancer cell apoptosis through improvement of ER-stress, which was further proved by unfolded protein response (UPR) pathway on basis of the upregulation of IRE1α, p-PERK, ATF6, and CHOP.

Three New Highly Oxygenated Germacranolides from Carpesium Divaricatum and Their Cytotoxic Activity

Three new highly oxygenated (2⁻4), and two known (1 and 5) 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 configuration of 1 was established using the circular dichroism (CD) method and X-ray diffraction, and the stereochemistry of the new compounds 2⁻4 were determined using similar CD spectra with 1. The new compound 2 and the known compound 5 exhibited potent cytotoxicity against hepatocellular cancer (Hep G2) and human cervical cancer (HeLa) cells, superior to those of the positive control cis-platin.

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.

Dicarabrol A, dicarabrone C and dipulchellin A, unique sesquiterpene lactone dimers from Carpesium abrotanoides

Three sesquiterpene lactone dimers with an unprecedented skeleton were isolated from the whole plants of Carpesium abrotanoides.

New Highly Oxygenated Germacranolides from Carpesium divaricatum and their Cytotoxic Activity

Eight highly oxygenated germacranolides (1–8) including four new ones (2–5) were isolated from the whole plant of Carpesium divaricatum. The planar structures and relative configurations of the new compounds were determined by NMR experiment and HRESIMS data. The absolute configuration of 1 was established by circular dichroism (CD) method and X-ray diffraction, and the stereochemistry of the new compounds 2–5 were determined by similar CD spectra with 1. Compound 2 is the first hydroperoxyl germacrane from the genus Carpesium. The ¹³C NMR data of 1, NMR data of 6–7, and their absolute configurations were reported for the first time. Two new compounds (2 and 4) and two known compounds (6 and 8) exhibited potent cytotoxicity against human cervical cancer (HeLa) cells, superior to that of the positive control doxorubicin.

Dicarabrol, a new dimeric sesquiterpene from Carpesium abrotanoides L

A new dimeric sesquiterpene, dicarabrol (1), together with three known sesquiterpenes, carabrol (2), 11(13)-dehydroivaxillin (3), and 2-desoxy-4-epi-pulchellin (4), were isolated from the whole plant of Carpesium abrotanoides L. Their structures were elucidated on the basis of spectroscopic analysis, and single crystal X-ray diffraction analysis. Compound 1 possessed a dimeric sesquiterpene core featured with a cyclopentane ring connecting two sesquiterpene lactone units rarely discovered in nature. Dicarabrol (1), as well as three known sesquiterpenes (2-4), had potent in vitro cytotoxicities against the K562, MCF-7, Hela, DU145, U937, H1975, SGC-7901, A549, MOLT-4, and HL60 cell lines with IC50 values ranging from 0.10 to 46.7 μM, while they showed significant antiviral (H1N1 and H3N2) activities. Furthermore, compounds 1, 3 and 4 displayed significant antimycobacterial activity (IC50 3.7, 6.0, and 7.6 μM, respectively).

Cs2CO3-promoted [3 + 2] cycloaddition providing an easy protocol toward imidazo[1,2-a]indole derivatives

A base-promoted [3 + 2] cycloaddition for the construction of multi-functionalized imidazo[1,2-a]indole derivatives with good yields has been accomplished.

Hot off the press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as coprisamide A from a bacterium isolated from Copris tripartitus.