A novel acetophenone, cynantetrone (1), was isolated from the rhizome of Cynanchum taiwanianum and its structure determined by spectroscopic methods. Compound 1 and cynandione B (3) showed significant in vitro cytotoxicity against T-24 cell lines, and 3 also against PLC/PRF/5 cell lines.
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Introduction. Β± In previous papers [1 Β± 4] we have reported the isolation and biological activity of acetophenones, i.e., of cynandiones A Β± D, cynanchone A, and 2,5dihydroxyacetophenone, from Cynanchum taiwanianum (Asclepiadaceae). In continuation of the investigation on bioactive constituents from this plant, a novel acetophenone, cynantetrone (1), was isolated from the rhizome of C. taiwanianum, and its structure was elucidated. The cytotoxic activity of 1, cynandiones A (2) and B (3), and cynanchone A (4) against some cell types are reported.
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Results and Discussion. Β± Compound 1, an orange powder, possesses the molecular formula C 66 H 44 O 20 as determined by DCI mass spectra (negative mode; [M Γ H] Γ at m/z 1155) and by H-and C-atom counting in NMR spectra. IR Absorptions were indicative of OH (3260 and 3430 cm Γ1 ), carboxylic-acid (1720 and 3560 cm Γ1 ), conjugated CO (1660 cm Γ1 ), and aromatic-ring moieties (1580 cm Γ1 ). The 1 H-and 13 C-NMR data ( Table 1), including NOESY, COSY, HMQC, and HMBC, suggested that 1 is a planar tetraacetophenone derivative with eight aromatic rings and two ether linkages (Fig. 1).