Total Synthesis, Cytotoxic Effects of Damnacanthal, Nordamnacanthal and Related Anthraquinone Analogues

Naturally occurring anthraquinones, damnacanthal (1) and nordamnacanthal (2) were synthesized with modified reaction steps and investigated for their cytotoxicity against the MCF-7 and K-562 cancer cell lines, respectively. Intermediate analogues 2-bromomethyl-1,3-dimethoxyanthraquinone (5, IC(50) = 5.70 ± 0.21 and 8.50 ± 1.18 μg/mL), 2-hydroxymethyl-1,3-dimethoxyanthraquinone (6, IC(50) = 12.10 ± 0.14 and 14.00 ± 2.13), 2-formyl-1,3-dimethoxyantharquinone (7, IC(50) = 13.10 ± 1.02 and 14.80 ± 0.74), 1,3-dimethoxy-2-methylanthraquinone (4, IC(50) = 9.40 ± 3.51 and 28.40 ± 2.33), and 1,3-dihydroxy-2-methylanthraquinone (3, IC(50) = 25.60 ± 0.42 and 28.40 ± 0.79) also exhibited moderate cytotoxicity against MCF-7 and K-562 cancer cell lines, respectively. Other structurally related compounds like 1,3-dihydroxyanthraquinone (13a, IC(50) = 19.70 ± 0.35 and 14.50 ± 1.28), 1,3-dimethoxyanthraquinone (13b, IC(50) = 6.50 ± 0.66 and 5.90 ± 0.95) were also showed good cytotoxicity. The target compound damnacanthal (1) was found to be the most cytotoxic against the MCF-7 and K-562 cancer cell lines, with IC(50) values of 3.80 ± 0.57 and 5.50 ± 1.26, respectively. The structures of all compounds were elucidated with the help of detailed spectroscopic techniques.