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Pale Indian plantain (Arnoglossum atriplicifolium (L.) H. Rob.) is a plant with traditional medicinal usage among the Cherokee Native American tribe for treating cancer. Two oplopane sesquiterpenoids were isolated from an extract of A. atriplicifolium from Western North Carolina. The compounds were isolated by bioassay-guided fractionation using an MCF-7 breast tumour cell line assay. The known compound (1S,6R,7R,8R)-1-acetoxy-6,7-diangeloxy-8,10-epoxy-2-oxo-oplopa-3,14Z,11,12-dien-13-al (1) had an EC50 value of 9.0 μM against MCF-7 cells, while the new compound (1S,3R,6R,7R,8R,11S)-1-acetoxy-6,7-diangeloxy-8,10,11,13-bisepoxyoplopan-2-one (2) had an EC50 value of 96 μM. The compounds were characterised by 1D and 2D NMR spectroscopy and by comparison with literature values in the case for 1. Based on NOESY analysis, a correction of the relative configuration for 1 is presented. The presence of these compounds may help to explain the folk remedy usage of this plant as an anticancer agent.

Two new triterpenoids (1, 2) and two new steroids (3, 4) along with twelve related known compounds (5-16) were isolated from the bark of Melia azedarach. The new structures were elucidated by means of spectroscopic methods and molecular modeling studies and found to be 21,24-cycloeupha-7-ene-3 β,16 β,21 α,25-tetrol (1), 3 β-acetoxy-12 β-hydroxy-eupha-7,24-dien-21,16 β-olide (2), 29-hydroperoxy-stigmasta-7,24(28) E-dien-3 β-ol (3), and 24 ξ-hydroperoxy-24-vinyl-lathosterol (4). All isolated compounds were tested for their cytotoxic activity against three human cancer cell lines (A549, H460, HGC27) using the CellTiter Glo™ luminescent cell viability assay. Among them, compounds 2- 4, 24 ξ-hydroperoxy-24-vinyl-cholesterol (6), kulinone (7), meliastatin 3 ( 8), 3-oxo-olean-12-en-28-oic acid (10), and (22 E,24 S)-5 α,8 α-epidioxy-24-methyl-cholesta-6,22-dien-3 β-ol (12) were found to have cytotoxic effects, with IC₅₀ values of 5.6-21.2 µg/mL., (© Georg Thieme Verlag KG Stuttgart · New York.)

Ten new triterpenoids, named meliasenins I-R (1-10), one new steroid (11), and 11 related known compounds (12-22) were isolated from fruits of Melia toosendan. The structures of the new compounds were established on the basis of spectroscopic methods, including 2D NMR techniques and mass spectrometry. The relative configuration of 1, (20R*,23E)-25-hydroperoxyeupha-7,23-diene-3β,16β-diol (meliasenin I), was confirmed by single-crystal X-ray diffraction analysis. All isolated triterpenoids (1-10, 12-15) and two steroids (11, 20) were tested for their cytotoxicity against U20S human osteosarcoma and MCF-7 human breast cancer cells using the MTT assay, and some of them were significantly cytotoxic (IC(50) <10 μg/mL). The insecticidal properties of compounds 1-15 and 20 were also briefly evaluated.