Investigation into tannins with antitumor properties led to the isolation of two new C-glycosidic ellagitannins (1 and 2) along with seven known ellagitannins (3–9) and a related polyphenolic constituent (10) from Lawsonia inermis leaves. Intensive HRESIMS, 1D and 2D NMR, and ECD spectroscopic analyses confirmed that compound 1 possesses a monomeric structure characteristic of a C-glycosidic tannin, while compound 2 exhibits a dimeric structure composed of a 2,3-O-hexahydroxydiphenoyl glucopyranose unit linked to a C-glycosidic tannin moiety. Among the known compounds, one (3) is a C-glycosidic tannin first isolated from nature, five are C-glycosidic ellagitannins—vescalagin (4), 1-O-methylvescalagin (5), castalagin (6), stachyurin (7), and casuarinin (8)—and one is an O-glycosidic ellagitannin, tellimagrandin II (9). The remaining phenolic constituent was identified as valoneic acid dilactone (10). The ellagitannins 1, 3–9 demonstrated significant cytotoxicity against human oral squamous cell carcinoma cell lines (HSC-2, HSC-4, and Ca9-22), with lower effects observed on human oral normal cells (HGF, HPC, and HPLF). Tellimagrandin II (9) exhibited the highest tumor-specific cytotoxicity and induced cleavage of poly (ADP-ribose) polymerase 1 (PARP1) in HSC-2 cells. These findings suggest that L. inermis ellagitannins hold potential as candidates for the development of anti-oral cancer agents.
The study focused on the phytochemical investigation of Lawsonia inermis, a plant traditionally used in herbal medicine and known for its dye-producing properties. The leaves were extracted using sequential solvent partitioning followed by chromatographic separation techniques including Diaion HP-20, MCI-gel CHP-20P, Toyopearl HW-40C, and preparative RP-HPLC. The structural elucidation of the isolated compounds relied heavily on advanced spectroscopic methods: high-resolution electrospray ionization mass spectrometry (HRESIMS), one-dimensional and two-dimensional NMR (1H, 13C, COSY, HSQC, HMBC), and electronic circular dichroism (ECD). Compound 1, named 1-O-methylflosin B, was characterized as an off-white amorphous powder with a molecular formula of C56H34O34, confirmed by HRESIMS m/z 1273.06317 [M + Na]+. Its NMR data revealed a glucose core with methoxy substitution at the anomeric position, connected via a C–C bond to a HHDP unit and further linked to a valoneic acid dilactone (VADL) moiety through ester linkages. The presence of VADL was supported by key HMBC correlations and ECD analysis indicating an aS configuration. Compound 2, reginin E, was identified as a dimeric ellagitannin with a molecular formula of C61H44O40, based on HRESIMS m/z 1439.CA I Antibody Autophagy 1278 [M + Na]+. It consists of two monomeric units: a 2,3-O-(S)-HHDP-D-glucose core and an open-chain glucose linked to a valoneoyl group. The dimeric nature was confirmed by duplicated signals in NMR spectra and HMBC correlations between aromatic protons and sugar carbons. The stereochemistry of both HHDP moieties was assigned as aS based on strong positive Cotton effects in their ECD spectra.Phospho-GSK3 β(Ser9) Antibody supplier
Compound 3, 1-O-methylstachyurin, was also isolated and structurally confirmed as a C-glycosidic ellagitannin with a methylated glucose core and identical aromatic moieties to stachyurin. All isolates were evaluated for cytotoxic activity against three human oral squamous cell carcinoma (HOSCC) lines—Ca9-22, HSC-2, and HSC-4—and three human oral normal (HON) cell types: gingival fibroblast (HGF), pulp cell (HPC), and periodontal ligament fibroblast (HPLF). The results showed that ellagitannins 1, 3–9 exhibited pronounced cytotoxicity toward malignant cells while showing minimal toxicity toward normal oral cells, indicating a favorable tumor-specific profile. Notably, tellimagrandin II (9) displayed the most potent activity with a CC50 value of 0.2 μg/mL against HSC-2 cells, and its tumor-specificity index (TS) reached 4.3, the highest among all tested compounds. This indicates superior selectivity for cancer cells over normal cells. The cytotoxicity of the tannins was not significantly altered by methylation at the C-1 position, suggesting that the glycosidic linkage pattern is more critical than methylation status for biological activity.
Further investigation focused on the mechanism of action of tellimagrandin II (9). Immunoblot analysis revealed that it induces cleavage of PARP1 in HSC-2 cells in a dose-dependent manner, confirming its ability to trigger apoptosis—a key pathway in cancer cell death.PMID:34893821 This effect was observed at concentrations ranging from 1 to 30 μg/mL, with significant cleavage evident at 10 μg/mL and above. Given that PARP1 inhibitors are currently used in targeted cancer therapies, particularly in BRCA-mutated cancers, the ability of tellimagrandin II to induce PARP1 cleavage highlights its potential as a lead compound for novel chemotherapeutic agents. Moreover, its natural origin and low toxicity to normal oral cells make it a promising candidate for development into anti-oral cancer therapeutics.
In conclusion, this study identifies two new C-glycosidic ellagitannins—1-O-methylflosin B (1) and reginin E (2)—from Lawsonia inermis leaves, along with several bioactive known tannins. The comprehensive structural characterization and biological evaluation demonstrate that these compounds possess selective cytotoxicity against oral cancer cells and can modulate key apoptotic pathways such as PARP1 cleavage. These findings support the continued exploration of L. inermis-derived ellagitannins as valuable sources of natural anticancer agents, particularly for oral cavity malignancies. Future research will focus on optimizing their delivery systems and evaluating their efficacy in vivo.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
