Comparison of the cytotoxic activities of naturally occurring hydroxyanthraquinones and hydroxynaphthoquinones

Seven hydroxyanthraquinone derivatives, 1–7, were isolated from the root of Rheum palmatum (Polygonaceae). Two propionated anthraquinone derivatives, 8 and 9, were synthesized. Four hydroxynaphthoquinone derivatives, 13, 14, 16 and 21, were isolated from the root of Lithospermum erythrorhizon Sieb. et Zucc. (Boraginaceae) and also three naphthoquinone derivatives, 19, 22 and 23, were isolated from the root of Macrotomia euchroma (Royle) Pauls. (Boraginaceae). The cytotoxicity of the anthraquinone and naphthoquinone derivatives on P-gp-underexpressing HCT 116 cells and P-gp-overexpressing Hep G2 cells was examined by MTT assay. Among the anthraquinone derivatives, compounds 3–5 which had OH, CH2OH and COOH substituent groups on the anthraquinone skeletons, respectively, showed potent growth inhibitory activities against both types of cancer cells (IC50 values: 5.7 ± 0.9 to 13.0 ± 0.7 μM in the case of HCT 116 cells and 5.2 ± 0.7 to 12.3 ± 0.9 μM in the case of Hep G2 cells). All hydroxynaphthoquinone derivatives isolated in this study exhibited extremely potent growth inhibitory activities against both types of cancer cells (IC50 values: 0.3 ± 0.09 to 0.46 ± 1.0 μM in the case of HCT 116 cells and 0.22 ± 0.03 to 0.59 ± 0.06 μM in the case of Hep G2 cells) as well as shikonin 10 (IC50 values: 0.32 ± 0.02 μM in the case of HCT 116 cells and 0.24 ± 0.03 μM in the case of Hep G2 cells).

Graphical abstractHydroxyanthraquinones (A type compounds) were isolated from Rheum palmatum (Polygonaceae). B type hydroxynaphthoquinones were isolated from Lithospermum erythrorhizon Sieb. et Zucc. (Boraginaceae) and C type hydroxynaphthoquinones from Macrotomia euchroma (Royle) Pauls. (Boraginaceae). The cytotoxicities of these quinones on P-gp-underexpressing HCT 116 cells and P-gp-overexpressing Hep G2 cells were compared.Figure optionsDownload full-size imageDownload as PowerPoint slide