Antiproliferative Activity and Effect on GABAA Receptors of Callitrisic Acid Derivatives

[EN] The semisynthesis and biological activity of the naturally occurring abietane diterpenoids callitrisic acid (4a; 4-epidehydroabietic acid) and callitrisinol (6) are reported. These compounds and jiadifenoic acid C (5) were obtained from methyl callitrisate (4b) isolated from Sandarac resin for biological evaluation and comparison with the biological activities of C4 epimers such as dehydroabietic acid (2a). In particular, the antiproliferative activity against a panel of six representative human solid tumor cell lines (A549, HBL-100, HeLa, SW1573, T- 47D, WiDr) and the effect on GABAA receptors (¿1ß2¿2s) were evaluated. The GI50 values were in the range of 3.4¿61 ¿M and the potentiation of IGABA was 269¿311 % at 100 ¿M. Callitrisinol (6) was found to be 6.7-fold more potent than the reference etoposide in the WiDr (colon) cancer cell line. The role of the stereogenic center at C4 for antiproliferative and GABAA receptor modulating activities in the dehydroabietane scaffold has thus been revealed.