Discovery of stereospecific cytotoxicity of (8R,8'R)-trans-arctigenin against insect cells and structure-activity relationship on aromatic ring.

One of the arctigenin stereoisomers, (8R,8'R)-trans-form 1, showed stereospecific cytotoxicity against insect cells, Sf9 and NIAS-AeAl-2 cells. By the comparison with other stereoisomers, the most importance of the 8'R stereochemistry for the higher activities was clarified. On the other hand, the wider range of activity level among stereoisomers against cancer cells, HL-60, was not observed. The structure-activity relationship research using derivatives bearing (8R,8'R)-trans-form was performed to show the same level of activities of 3-iodo, 4-iodo, and 3,4-methylenedioxy derivatives 28, 29, and 36 as (8R,8'R)-trans-arctigenin 1. In the examination of thiono derivatives, 4-iodo thiono and 3,4-methylenedioxy thiono derivatives 66, 67 showed similar level of activities to that of (8R,8'R)-trans-arctigenin 1. The expression of ribosomal 28S rRNA gene of Sf9 cells was increased by (8R,8'R)-trans-arctigenin 1, whereas a degradation of DNA was not observed.