Novel cembranoid diterpenoids from the leaves of <i>Nicotiana tabacum</i> with anti-proliferative activity

Phytochemical investigation of the leaves of Nicotiana tabacum L. led to the isolation of eleven compounds, including nine known compounds (1–5, 8–11) and two previously undescribed cembranoid diterpenes (6 and 7). The known compounds were identified by analysis of spectroscopic data and comparison with literature data, while the structures of the two new cembranoid diterpenes were elucidated by analysis of spectroscopic (NMR and ECD) and spectrometric data (HRMS). Both new cembranoid diterpenes were screened against A549, HL-60, HeLa and MRC-5 cell lines. Compound 6 demonstrated strong anti-proliferative activity against HL-60 cells (IC50 = 9.9 µM), while compound 7 displayed strong activity against HeLa cells (IC50 = 6.2 µM). Notably, both compounds showed low cytotoxicity towards normal MRC-5 cells (IC50 > 67 µM), with selectivity indices (SI) exceeding 4 for all tested cancer cell lines, indicating favourable selective anti-proliferative effects.