| Abstract
| - Two cytotoxic rocaglate derivatives possessing an unusual dioxanyloxy unit, silvestrol (1) andepisilvestrol (2), were isolated from the fruits and twigs of Aglaia silvestris by bioassay-guidedfractionation monitored with a human oral epidermoid carcinoma (KB) cell line. Additionally, twonew baccharane-type triterpenoids, 17,24-epoxy-25-hydroxybaccharan-3-one (3) and 17,24-epoxy-25-hydroxy-3-oxobaccharan-21-oic acid (4), as well as eleven known compounds, 1β,6α-dihydroxy-4(15)-eudesmene (5), ferulic acid (6), grasshopper ketone (7), apigenin, cabraleone, chrysoeriol, 1β,4β-dihydroxy-6α,15α-epoxyeudesmane, 4-hydroxy-3-methoxyacetophenone, 4-hydroxyphenethyl alcohol,ocotillone, and β-sitosterol 3-O-β-d-glucopyranoside, were also isolated and characterized. Thestructures of compounds 1−4 were elucidated by spectroscopic studies and by chemical transformation. The absolute stereochemistry of silvestrol (1) was established by a X-ray diffraction study ofits di-p-bromobenzoate derivative, and the structure of 3 was also confirmed by single-crystal X-raydiffraction. The isolates and chemical transformation products were evaluated for cytotoxicityagainst several human cancer cell lines, and silvestrol (1) and episilvestrol (2) exhibited potent invitro cytotoxic activity. Silvestrol (1) was further evaluated in vivo in the hollow fiber test and inthe murine P-388 leukemia model.
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