Eight new cembranoids, boscartins A-H (1, 2, and 4-9), and the known incensole oxide were isolated from the gum resin of Boswellia carterii. The absolute configurations of 1, 2, 4, and incensole oxide were unequivocally resolved using single-crystal X-ray diffraction analysis with Cu Kα radiation, and the absolute configuration of 5 was resolved via electronic circular dichroism data. The antiulcerative colitis activities of the compounds were evaluated in an in vitro x-box-binding protein 1 (XBP 1) transcriptional activity assay using dual luciferase reporter detection. At 10 μM, compounds 1, 5, 6, and 7 significantly activated XBP 1 transcription with EC50 values of 0.34, 1.14, 0.88, and 0.42 μM, respectively, compared with the pGL3-basic vector control.
Chemical examination of the exuded gum resin of Boswellia carterii resulted in the isolation of nine new prenylaromadendrane-type diterpenes, boscartols A-I (1-9). The structures of these compounds were established by extensive 1D and 2D NMR spectroscopic analyses, mass spectrometric data, and circular dichroism spectra. Compounds 1-3, 5, 6, 8, and 9 (10 μM) showed moderate hepatoprotective activity against d-galactosamine-induced HL-7702 cell damage.
Six new phenolic diglycosides, named gymnetinosides A-F (1-6), were isolated from the ethanolic extract of Gymnema tingens, together with three known diglycosides, sequinoside K (7), khaephuoside B (8), and albibrissinoside A (9). The structures of the new compounds were determined by spectroscopic techniques including 1D-, 2D NMR, mass spectroscopy, and circular dichroism. Compounds 1, 5, and 6 showed hepatoprotective activities against D-galactosamine-induced HL-7702 cell damage.
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