Structural Modification of Sylibin to Derivatives of Sylibin/Hydnocarpin D /Silandrin, and Evaluation of Their Cytotoxicity Against Cancer Cells
Background: Flavonolignans like silybin, hydnocarpin, and siliandrin are a group of natural compounds combining the structural moieties of flavonoid and phenylpropanoid (lignan). Hydnocarpin and silandrin were less explored because of trace occurrence in nature. Objective: The present study aimed to develop a chemical conversion of silybin to hydnocarpin, and siliandrin. Also, a series of amide derivatives would be synthesized and biologically evaluated with regard to their anti-cancer effects. Methods: In order to selectively convert silybin to 23-iodo silybin, 23-iodo hydnocarpin D and 23-iodo isosilandrin, the ratio of Ph3P, imidazole and molecular iodine was meticulously adjusted. These three iodide compounds were converted into amide compounds by chemical transformation. MTT method was applied to evaluate their anti-cancer potency. The binding affinity to related proteins was calculated by molecular docking. Results: Totally, 45 new amido-derivatives were synthesized and structurally characterized by NMR and HRMS. Some of them showed moderate to good antiproliferative potency against cancer cells. The activity of compound 10j was further testified by colony formation assay and molecular docking. Conclusion: Synthesis of 23-iodo silybin, 23-iodo hydnocarpin D and 23-iodo isosilandrin from silybin was successfully accomplished by one simple iodination reaction. Some of the amide derivatives of sylibin/hydnocarpin D /silandrin exhibit a remarkable inhibitory effect of proliferation on cancer cells as compared to silybin. These results would pave the way for further investigation on the derivatives of flavonolignans for the treatment of cancer.