Cytotoxic Activity of Diterpenoids from Rabdosia japonica var. glaucocalyx

Abstract

The cytotoxicity of five diterpenoids (Glaucocalyxins A-E) from the whole plant of Rabdosia japonica var. glaucocalyx against four human tumor cell lines (HL-60,6T-CEM, LOVO and A549) was tested, respectively. The results suggested that Glaucocalyxins A, B and D showed an apparent activity with IC50 values from 0.0490 to 2.65 μg/mL. Glaucocalyxin A showed a strong activity (IC₅₀ = 0.0490 μg/mL) against 6T-CEM cells, which is stronger than that of doxorubicin (IC₅₀ = 0.0809 μg/mL). However, Glaucocalyxins C and E exhibited no cytotoxic activities against the four cell lines with IC₅₀ values higher than 100 μg/mL. Furthermore, Glaucocalyxins A, B, D and X exhibited the cytotoxicity in the order: A > B > D > X. Therefore, the structure-activity relationship of the diterpenoids can be concluded that the a,b-unsaturated ketone moiety in ring D is the leading active sites; OH-7 and OH-14 play an important role in keeping the cytotoxicity.