The plant itself carries an impressive ethnobotanical pedigree. Species of the genus Carpesium have been employed in traditional Chinese medicine as antipyretic, anti-inflammatory, analgesic, antifungal, antibacterial, and antitumor remedies, and C. abrotanoides in particular has a folk-medicine history spanning antiparasitic, insecticidal, antidiabetic, antioxidant, and anti-inflammatory uses. Earlier phytochemical work established that sesquiterpenoids, fifteen-carbon terpene molecules built from three isoprene units, are the characteristic chemical signature of this species. The genus produces an unusually broad spectrum of skeletal architectures, including eudesmanolides, guaianolides, germacranolides, and even large dimeric assemblies in which two sesquiterpene units are joined together. Prior studies had also hinted at anticancer potential: an ethanol extract of the whole plant was shown to activate the Nrf2/NQO1 antioxidative pathway and trigger G2/M cell cycle arrest and apoptosis in colon cancer cells, while individual sesquiterpenoids could induce protective autophagy in various cancer lines.

To mine this chemical diversity systematically, the researchers collected twenty kilograms of dried, powdered branches and leaves from plants gathered in Baishan City in China’s Jilin Province and extracted the material with ninety-five percent ethanol. After concentrating the crude extract to more than 1.3 kilograms and partitioning it into an ethyl acetate-soluble fraction, they deployed a battery of chromatographic techniques, including macroporous resin, silica gel columns, Sephadex LH-20 gel filtration, and semipreparative high-performance liquid chromatography on both reversed-phase and chiral columns. The painstaking fractionation ultimately delivered twenty-eight pure compounds, each verified to greater than ninety-five percent purity by nuclear magnetic resonance analysis.

Structural elucidation of the five new molecules demanded a full forensic toolkit of modern spectroscopy. Carpabrotane A, for example, revealed a molecular formula of C14H18O5 by high-resolution mass spectrometry, indicating six degrees of unsaturation. Its proton and carbon NMR spectra showed an alpha,beta-unsaturated ketone, two epoxy rings spanning the C-1/C-10 and C-4/C-5 positions, and a five-membered lactone fused to the ring system, all features that together defined a rare 13-nor-germacrane skeleton, a sesquiterpene framework missing one carbon from the standard thirty-carbon count. Nuclear Overhauser effect correlations established which protons sat on which face of the molecule, and a single crystal grown from a dichloromethane-methanol mixture allowed single-crystal X-ray diffraction to lock down the absolute configuration as 1R,4R,5R,8S,10R with unambiguous precision.

The other new compounds showcased complementary structure-solving strategies. Carpabrotane B presented a tricyclic 5/7 fused carbocyclic core characteristic of a 13-nor-pseudoguaiane skeleton, and its absolute configuration was assigned by comparing its experimental electronic circular dichroism spectrum with spectra calculated using time-dependent density functional theory, a computational method that predicts how chiral molecules absorb circularly polarized light. Carpabrotane C turned out to be a twelve-carbon fragment differing from a known compound only by the migration of a hydroxyl group from position 4 to position 3, while carpabrotanes D and E were distinguished from known relatives by hydroxyl migration and by epimerization at a single stereocenter, respectively. Notably, the team also resolved long-standing ambiguities in the literature: the absolute configurations of three known compounds, including the eudesmanolide telekin, were established for the first time through X-ray crystallography and ECD calculations, correcting a gap that had persisted since their original isolation.

With all twenty-eight compounds in hand, the researchers turned to biology, screening each one for cytotoxicity against NCI-H1975 cells using the CCK-8 colorimetric assay over seventy-two hours. Two molecules dominated the results. Compound 25, the known eudesmanolide 5-alpha-epoxyalantolactone, showed an IC50 of 0.93 micromolar, while compound 13, the pseudoguaiane 2-desoxy-4-epi-pulchellin, came in at 3.68 micromolar. Both figures markedly surpass the positive control gefitinib, an approved EGFR inhibitor that managed only 9.27 micromolar against this resistant cell line. Because compound 25 had already been well characterized in prior work, including as the first small-molecule inhibitor of the annexin A2 protein, and because its natural yield was too low for extensive follow-up, the team prioritized compound 13 for mechanistic study.

What they found gives compound 13 an unusual pharmacological fingerprint. Western blot analysis after twenty-four hours of treatment revealed pronounced downregulation of three key cell-cycle regulators: Cyclin A1, which drives cells through S phase; CDC2, the kinase that propels entry into mitosis; and c-MYC, the master transcriptional controller of proliferation. Flow cytometry confirmed the functional consequence, showing a dose-dependent accumulation of cells in S phase, with a ten micromolar dose increasing the S-phase population by 1.5-fold relative to untreated controls. In parallel, levels of cleaved PARP, the canonical molecular signature of apoptosis, rose sharply, and Annexin V staining demonstrated concentration-dependent programmed cell death. Compound 13 thus operates as a dual-function agent, simultaneously halting DNA replication and dismantling the cell’s survival machinery.

This S-phase arrest mechanism is relatively uncommon among natural anti-lung-cancer agents, and the contrast with related molecules is instructive. The structurally similar 5-alpha-epoxyalantolactone induces G2/M arrest and reactive oxygen species accumulation, while santamarine, another plant sesquiterpenoid, kills lung adenocarcinoma cells through oxidative stress-mediated mitochondrial dysfunction and NF-kappa-B inhibition. A compound that combines cytostatic S-phase blockade with cytotoxic apoptosis may carry a therapeutic advantage, because forcing tumor cells through two distinct bottlenecks could reduce the likelihood that resistance mutations allow escape, a persistent problem in non-small-cell lung cancer treatment.

Comparing activity across all twenty-eight compounds also yielded preliminary structure-activity relationships that could guide medicinal chemistry. The alpha-methylene-gamma-lactone motif, an exocyclic double bond conjugated to a gamma-lactone ring, emerged as the key pharmacophore: compounds bearing it, including 25, 13, 6, and 9, were consistently the most potent, while those lacking it showed markedly reduced activity. A single hydroxyl group at position 4 or 5 proved beneficial, but multiple hydroxyls diminished potency, likely by reducing the molecules’ ability to cross cell membranes. An epoxide at positions 5 and 6 enhanced activity in compound 25 but not in its diastereomer 26, underscoring how three-dimensional orientation governs biological effect. Eudesmanolides and pseudoguaianes generally outperformed guaianolides, and the two nor-sesquiterpenoids were the least active of all.

Much work remains before any of these molecules approaches the clinic. The mechanistic studies were conducted in a single cell line, the structure-activity relationships remain preliminary, and compound 13’s molecular target has not yet been identified. Nevertheless, the study demonstrates how classical natural products chemistry, when paired with modern crystallography, computational spectroscopy, and rigorous cancer biology, can still surface genuinely novel chemical matter from medicinal plants. With five new skeletons mapped, three old configurations corrected, and a dual-mechanism lead compound in hand, Carpesium abrotanoides has earned its place on the growing list of traditional remedies whose chemistry may yet translate into modern anticancer therapeutics.

Subject of Research: Anti-NSCLC sesquiterpenoids isolated from Carpesium abrotanoides

Article Title: Sesquiterpenoids from Carpesium abrotanoides with structural diversity and anti-NSCLC activity

Article References: Tang, G.-H., Ling, L., Zhao, Z.-T., Huang, C.-J., Li, L., Wu, S.-Q., Cui, Y.-J., Jiang, L., Gan, L., Yin, S., & Pu, R. (2026). Sesquiterpenoids from Carpesium abrotanoides with structural diversity and anti-NSCLC activity. Results in Chemistry, 31, Article 103936. https://doi.org/10.1016/j.rechem.2026.103936

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103936

Keywords: Carpesium abrotanoides, sesquiterpenoids, non-small-cell lung cancer, natural products, cell cycle arrest, apoptosis, X-ray crystallography, structure-activity relationships, carpabrotanes, NCI-H1975, eudesmanolides, pseudoguaianes