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4), have been synthesized and characterized by elemental analysis, IR, and 1 H and 13 C NMR spectra. The crystal structures of 1 and 4 have been determined by X-ray single crystal diffraction and show that the tin atom possesses a distorted tetrahedral geometry. Intermolecular O−H···O hydrogen bond in 1 connects neighboring molecules into a cyclic tetramer. The in vitro cytotoxicity of the compounds against the human tumor cell lines A549 was found to be higher than that of cis-platin used clinically.

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Summary. Scutellaria barbata D. Don has been used as a traditional Chinese medicine for antitumor and anti-inflammatory. However, there were just a few investigations about S. barbata D. Don according to bioactivity-directed isolation and online identification for the chemical constituents. In this work, eight compounds were isolated from S. barbata D. Don. The three flavonoids indicated the cytotoxic activity against human leukemic Reh cell lines. In addition, the constituents of S. barbata D. Don were further characterized and identified by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC−Q-TOF-MS). The UHPLC− Q-TOF-MS method was in negative ion mode. HPLC separation was performed on a Tosoh TSK gel ODS-100V (4.6 × 150 mm, 3.0 µm) column by gradient elution using water containing 0.3% formic acid and acetonitrile as mobile phase at a flow rate of 0.8 mL min −1 . A total of 18 compounds, including 4 phenolic acids and 14 flavonoids were tentatively characterized and identified by means of the retention time, accurate mass, and characteristic fragment ions.