| Abstract
| - In a continuation of our search for potential tumor inhibitors from plants, it was found that the CH2Cl2−MeOH (1:1) extracts from Digitalispurpurea and Penstemonlinarioides both showed PKCα-inhibitorybioactivity. Bioassay-directed fractionation of the extract from D. purpurea yielded the new, weakly activephenylethanoid glycoside 2-(3-hydroxy-4-methoxy-phenyl)-ethyl-O-(α-l-rhamnosyl)-(1→3)-O-(α-l-rhamnosyl)-(1→6)-4-O-E-feruloyl-β-d-glucopyranoside (1) together with the four known compounds calceolarioside A (2), calceolarioside B (3), forsythiaside (4), and plantainoside D (5). The extract from P. linarioidesyielded the three known glycosides leucosceptoside A (6), acteoside (7), and poliumoside (8), togetherwith the iridoid plantarenaloside (9). All of the isolated compounds, except compound 9, showed inhibitoryactivity against PKCα with IC50 values (in μM) of 125 (1), 0.6 (2), 4.6 (3), 1.9 (4), 14.8 (5), 19.0 (6), 9.3 (7),and 24.4 (8).
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