Bioassay-guided isolation of cytotoxic constituents from the flowers of Aquilaria sinensis
Jun Yang, Dong‐Bao Hu, Mengyuan Xia, Ji‐Feng Luo, Xingyu Li, Yue‐Hu Wang
Abstract
Abstract Bioassay-guided fractionation of the EtOH extract from the flowers of Aquilaria sinensis (Lour.) Spreng. (Thymelaeaceae) led to the isolation of a new cucurbitane-type triterpenoid, aquilarolide A ( 1 ), along with five known compounds ( 2 – 6 ). The structure of 1 was elucidated by extensive 1D and 2D nuclear magnetic resonance (NMR) experiments and mass spectrometry (MS) data and theoretical calculations of its electronic circular dichroism (ECD) spectra. Aquilarolide A, cucurbitacin E ( 3 ), cucurbitacin B ( 4 ), and 7-hydroxy-6-methoxy-2-[2-(4-methoxyphenyl)ethyl]-4 H -1-benzopyran-4-one ( 6 ) showed significant cytotoxicity against human lung adenocarcinoma SPC-A-1, human lung squamous cell carcinoma NCI-H520, human lung adenocarcinoma A549, and paclitaxel-resistant A549 (A549/Taxol) cell lines. All four active compounds, with IC 50 values ranging from 0.002 to 0.91 μM, had better inhibitory activities against A549/Taxol cells than paclitaxel (IC 50 = 1.80 μM). Among them, cucurbitacin E (IC 50 = 0.002 μM) is the most active. Further studies are needed to evaluate their in vivo antitumor activities and to clarify their mechanisms. Graphical Abstract