The Design, Synthesis , And Anti-tumor Activities Of DMAKO-20 As A Shikonin Oxime Derivative

Cancer is a kind of disease that seriously threaten the human health.Finding new anti-cancer compounds from natural products has become a hot spot in current research.Shikonin and alkannin,the main active ingredient of Lithospermum,have been proved to have antitumor effects for their naphthazarin mother nucleus can generate reactive oxygen species and alkylate key endogenous nucleophiles.However,these two compounds failed to become candidate drugs because of their wide toxicity.In our previous study,alkannin oxime derivative was obtained by structural modification and evaluated as an strong anti-cancer compound in vitro and in vivo.Though DMAKO-20 was unable to generate reactive oxygen species or alkylate biomacromolecule by sheltering the naphthazarin mother nucleus by the oxime group,enhanced selective anti-proliferative activity was exhibited in vitro and in vivo evaluation.The further development of this compound is also limited due to unclear anti-tumor mechanism and poor water solubility.Based on the previous synthetic method of shikonin oxime derivatives and optimized conditions,target compound was synthesized by 11-stage process starting from1,5-dihydroxynaphthalene with overall yields of 10.6%.(S)-2-(1-isopentyloxy 4-methyl-3-pentenyl)-1,4,5,6 8-tetramethoxide naphthalene as a key intermediate was prepared by using asymmetric hydrogenation of shikonin ketone.In this way,the product of invalid R-isomer was avoided,compared with the reported splitting method.In addition,2-carbonyl was converted to 6-carbonyl on naphthazarin mother nucleus by reduction,methylation and oxidation,which increased the overall yield.Additionally,the synthetic procedure was simple and easy to be industrialized.Previous study indicated that the anti-tumor activity of DMAKO-20 was significantly decreased by combination of ?-naphthoflavone,which is recognized as a strong inhibitor of the CYP1B1 enzyme.On the basis of the molecular docking and in vitro metabolism study of DMAKO-20,this research paper revealed plausible metabolic pathways of this compound,which is mediated by CYP1B1 enzyme.In order to increase water solubility,prodrug principle as a kind of drug design strategy was applied and the water soluble prodrug DMAKO-20 derivatives were designed,synthesized and evaluated their anti-cancer activities in vitro and in vivo.The results demonstrated that glucosyl and nicotinate substituted DMAKO-20 derivatives showed good water solubility and similar anti-tumor activity compared with the prototype drug.From other perspective,it suggested the two compounds could be a good starting point for the development of novel lead compounds in the fight against cancer.In summary,the optimized synthetic route for DMAKO-20,preliminary study on action mechanism and prodrug structural modification were performed in our study and DMAKO-20 derivatives with good water solubility and strong anti-tumor activity were obtained.Our study laid a good foundation for subsequent developement of anti-tumor drugs.