Purpose: Daphne mucronata Royle grown in Iran has shown anticancer activities against different cancer cell lines. Therefore, within this study, we investigate the phytochemical pattern of this plant.
Method: Phytochemical investigation was done using standard column chromatography system: The structures were recognized by the interpretation of one and two-dimensional nuclear magnetic resonance (NMR) spectra and the help of High-Resolution Electrospray Ionization Mass spectroscopy (HR-ESIMS) and Infrared spectroscopy (IR) data. Stereochemistry was determined using 2D and 3D NOESY, and comparison of coupling constant values with literature. The absolute configuration was determined and confirmed using specific rotation and electronic circular dichroism experiments. Cytotoxicity was done against HeLa cells by standard MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Luciferase assay was used to check if the compounds can inhibit the activation of cancer-related signaling pathways. Molecular docking simulation was done for biological activity evaluation and to examine the interaction of the ligand with each of the proteins.
Results: A new sesquiterpenoid, 4,11(12)-guiadiene-1-ol-3-one (4), together with eight specialized metabolites, betulinic acid (1), coniferyl aldehyde (2), oleanolic acid (3), daphnetoxin (5), apigenin (7), syringin (8), and genkwanol A (9) were isolated and reported for the first time from the shoots of the plant. Compound 4 as an undescribed compound was submitted for cytotoxicity assay and showed moderate activity with the IC50 value of 51.3 ± 4.2 μM against HeLa cancer cells. It showed selective inhibition of Interleukin-6 mediated signal transducer and activator of transcription 3 pathway (STAT-3/ IL-6), and Smad protein / transforming growth factor beta (TGF-β) transcription factors when screened through an array of cancer signaling pathways. Molecular docking confirmed biological tests and showed the interaction with STAT3 and Smad proteins.
Conclusion: An undescribed sesquiterpenoid: 4,11(12)-guiadiene-1-ol-3-one in addition to eight known compounds were isolated. The new sesquiterpene was evaluated for the luciferase assay on 14 main cancer-related signaling pathways and showed selective inhibition of STAT3/IL6, and Smad/ TGF-β transcription factors. Molecular docking simulation showed more interactions with STAT3 than Smad, which confirms better interaction of compound 4 with STAT3 than Smad proteins. Graphical abstract.
Keywords: Cancer signaling; Daphnemucronata; Luciferase assay; Molecular docking; STAT; Smad.