Enkleia siamensis Kurz (Thymeliaceae) is a climbing shrub commonly distributed throughout the northeastern region of Thailand. An ethanolic extract of the dried roots was found to be active in the P-388 in vitro cytotoxicity assay (ED50 0.1 µg/ml). Bioassay-directed fractionation of the total alcoholic extract resulted in the isolation of three coumarins, clausarin, nordentatin, and daphnoretin.Clausarin and nordentatin were obtained from the petroleum ether fraction of the ethanolic extract.Clausarin was identified by comparing its spectra ('H nmr, uv, ir, ms) with published data (1,2). Norden-
Enkleia siamensis Kurz (Thymelaeaceae) is a climbing shrub commonly found in the northeastern region of Thailand. In a previous communication (1), we have reported on the isolation of three bioactive coumarins, namely, clausarin, daphnoretin, and nordentatin, from a cytotoxic extract of the roots. Further examination of the CHC13 fraction has now led to the isolation of two known compounds, identified as (-)-eudesmin, chamaej asmin(e), and a new isoquinolone alkaloid, enkleine (1), each of which was devoid of significant cytotoxic activity when tested in the KB and P-388 cell culture systems. The first isolate, m.p. 104-106°C, [a]0: 705° was identified as the lignan (-)-eudesmin. Its NMR and mass spectra were consistent with the general structure of eudesmin (2, 3), but the specific optical rotation indicates that it is antipodal to the common (+)-isomer.
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