Cytotoxicities of cucurbitacins from the stem bark of Aquilaria sinensis.

One previously undescribed cucurbitacin, 11-hydrocucurbitacin B (1), and five known analogs, 3-epicucurbitacin Q1 (2), cucurbitacin Q1 (3), cucurbitacin D (4), isocucurbitacin D (5), and hemslecin A (6), were isolated from the stem bark of Aquilaria sinensis (Thymelaeaceae). The chemical structure of 11-hydrocucurbitacin B was elucidated by MS and NMR analysis and ECD calculations. All the isolates were evaluated for their cytotoxicity against seven human cancer cell lines, namely, gastric cancer HGC-27 and AGS cells, leukemia HL-60 cells, breast cancer MDA-MB-231 cells, colon cancer SW480 cells, lung adenocarcinoma A549 cells, and paclitaxel-resistant A549 (A549/Taxol) cells, in addition to the normal human bronchial epithelial cell line BEAS-2B. Cucurbitacin Q1 exhibited the most potent inhibitory activity against these seven cancer cell lines, with IC 50 values ranging from 0.017 μ M to 7.68 μ M. The previously undescribed compound, 11-hydrocucurbitacin B exhibited moderate inhibitory effects on AGS (IC 50 = 2.66 μ M), HGC-27 (IC 50 = 0.54 μ M), SW480 (IC 50 = 3.94 μ M), A549 (IC 50 = 0.51 μ M), and A549/Taxol (IC 50 = 2.39 μ M) cell lines, with low toxicity toward normal BEAS-2B cells (IC 50 ˃ 40 μ M). [Display omitted] • Six cucurbitacins were isolated from the stem bark of Aquilaria sinensis. • 11-Hydrocucurbitacin B was cytotoxic to AGS, HGC-27, SW480, A549, and A549/Taxol cells. • 11-Hydrocucurbitacin B exhibited low toxicity toward normal BEAS-2B cells. [ABSTRACT FROM AUTHOR]