Chrysophanol and 1,8-di-O-hexylchrysophanol derivatives having nucleic acid bases at position 5 were synthesized. Furthermore, derivatives of menadione substituted at position 11 (type A naphthoquinone derivatives) or methylmenadione substituted at position 7 (type B naphthoquinone derivatives) modified with nucleic acid bases, amines and thiocyano, selenocyano or thioacetyl groups were synthesized. The cytotoxic effects of these derivatives on HCT 116 cells, which poorly express P-glycoprotein (P-gp), and Hep G2 cells, which stably express P-gp, were evaluated by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results were compared with those obtained using 5-fluorouracil (5-FU), which has been used clinically. Several of these derivatives exhibited markedly higher potent cytotoxic effects not only on HCT cancer cells but also Hep G2 cancer cells as compared with 5-FU.

AbstractSynthesis and biological evaluation of chrysophanol and menadione derivatives are described.

1,8-di-O-alkylaloe-emodin derivatives (namely, methyl-, propyl-, hexyl-, dodecyl-, and octadecyl) were synthesized from naturally occurring aloe-emodin. Further, derivatives having various substituents such as diethylamino, pyrrolidinyl, piperidinyl, methylpiperazinyl, imidazolyl, thiocyano and selenocyano groups at the 15 position of chrysophanol and 1,8-di-O-hexylchrysophanol from aloe-emodin were synthesized. The cytotoxic effects of these derivatives on less P-glycoprotein (P-gp)-expressing HCT 116 cells and stably P-gp-expressing Hep G2 cells were evaluated by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Among these products, several of them exhibited markedly higher potent cytotoxic effects not only on HCT116 cells but also Hep G2 cancer cells as compared to aloe-emodin.

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).

26-Iodopseudodiosgenin (8) and 26-iodopseudodiosgenone (9) were reacted with various nucleophiles (KSCN, KOCN, NaCN, NaN(3) and various amines) to give pseudodiosgenin derivatives (4, 12, 16-20, 26) and pseudodiosgenone derivatives (5, 13, 21-25, 27), respectively. The reactions of 8 and 9 with KOCN gave the elimination products (10) and (11), respectively. The reaction of 9 with NaCN gave 5alpha,26- (14) and 5beta,26-dicyanocholestan-3-one (15). The reaction of 8 with NaN3 gave triazepine derivative (30), while that of 9 gave 26-azidopseudodiosgenone (31). Compound 31 was converted into triazepine derivative (32) by heating at 120 degrees C. The cytotoxicity of the pseudodiosgenins and pseudodiosgenones on P-gp-underexpressing HCT 116 cells and P-gp-overexpressing Hep G2 cells was examined by MTT assay. Pseudodiosgenins 2, 4, 12 and 30 showed strong cytotoxic activity (IC50 values: 2.6+/-0.3-6.7+/-1.4 microM), as did pseudodiosgenones 3, 5, 11, 13, 21-25 and 27 (IC50 values: 1.3+/-0.3-6.4+/-0.3 microM) toward HCT 116 cells. Pseudodiosgenins 12, 16 and 30 (IC50 values: 1.2+/-0.7-2.2+/-0.6 microM) and pseudodiosgenones 22, 23, 25 and 27 (IC50 values: 0.6+/-0.1-2.5+/-0.3 microM) were highly cytotoxic to Hep G2 cells. Compounds 3 and 27 showed efficient antibacterial activity (MIC: 15.6, 10.4 microg/ml) and (MIC: 7.8, 15.6 microg/ml) against Bacillus subtilis and Staphylococcus aureus, respectively.