Design, synthesis, and cytotoxicity evaluation of threonine-based galactoceramide with aromatic groups and various fatty-acyl side chains

Abstract

In galactoceramides, presence of fatty-acyl group on amide moiety or phytosphingosine group is some of the important features that influence the cytotoxicity. Continuous efforts are in progress to modify the fatty-acid moiety and phytosphingosine group present on the galactoceramides to enhance the cytotoxic potential of these compounds. Hence, in the present study, threonine-based β-galactoceramide and its derivatives were prepared by modifying the fatty-acyl group on amide moiety with different fatty-acyl moieties and aromatic acids employing trichloroacetimidate methodology. The structurally related threonine-based ceramide part was synthesized in multi-step process using different reagents. The ceramide part was glycosylated with galactose using trichloroacetimidate as donor. Further, all the synthesized compounds were evaluated for in vitro cytotoxicity against three cancer cell lines and one normal cell line and all the compounds exhibited good to moderate cytotoxicity against all the tested cancer cell lines. In aromatic derivatives, the compound 8i exhibited promising activity against MCF7, A549 and HeLa cancer cell lines with IC50 values of 14.08, 14.78, and 16.70 µM, respectively. In fatty-acid derivatives, two compounds exhibited promising activity, i.e., compound 8m against HeLa with IC50 value 16.34 µM and compound 8n against MCF7 with IC50 value 18.05 µM. Based on structure–activity relationship, aromatic acid derivatives exhibited potential activity as compared to fatty-acid derivatives. Further, the influence of some of the key factors such as spacer chain length between aromatic residue and amide functional group, methoxy substituents on aryl group, terminal unsaturation of fatty acid and branching chain effect on the cytotoxicity are discussed.