Three New Cytotoxic ent-Kaurane Diterpenes from Isodon excisoides
2015
Li-Ping Dai | Chun Li | Han-Ze Yang | Yan-Qing Lu | Hong-Yan Yu | Hui-Min Gao | Zhi-Min Wang
Three types of ent-kaurane diterpenoids were isolated from the aerial parts of Isodon excisoides, including three new diterpenoids, 1α,7α,14β-trihydroxy-20-acetoxy-ent-kaur-15-one (1): 1α,7α,14β,18-tetrahydroxy-20-acetoxy-ent-kaur-15-one (2): and 1α-acetoxy-14β-hydroxy-7α,20-epoxy-ent-kaur-16-en-15-one (3): together with six known diterpenes henryin (4): kamebanin (5): reniformin C (6): kamebacetal A (7): kamebacetal B (8): and oridonin (9). The structures of the isolated compounds were elucidated by means of nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry in conjunction with published data for their analogs, as well as their fragmentation patterns. Compounds 5 and 9 were isolated from Isodon excisoides for the first time. To explore the structure-activity relationships of the isolated compounds, they were tested for their cytotoxic effects against five human cancer cell lines: HCT-116, HepG2, A2780, NCI-H1650, and BGC-823. Most of the isolated compounds showed certain cytotoxic activity against the five cancer cell lines with IC50 values ranging from 1.09–8.53 µM. Among the tested compounds, compound 4 exhibited the strongest cytotoxic activity in the tested cell lines, with IC50 values ranging from 1.31–2.07 µM. Compounds 1, 6, and 7 exhibited selective cytotoxic activity.
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