Synthesis of ester derivatives of Rhein and their in vitro antitumor activities on cervical cancer cells (Hela)

Abstract

Taking Rhein as the lead compound, ten esters of rhein were synthesized by esterification. For synthesis of smaller steric hindrance alcohols, SOCl₂ was used as a catalyst to synthesize methyl, ethyl and butyl esters. For lager steric hindrance alcohols, dicyclohexyl carbodiimide (DCC) was used as dehydrating agent, and 4-dimethylaminopyridine (DMAP) was used as the catalyst to synthesize isopropyl, isobutyl, tertbutyl, isoamyl, benzyl, 2-phenyl ethyl, 2-chloroethyl esters. Structural characterization of the target compounds were done using melting point, ¹H NMR, ¹³C NMR and HRMS. Five out of the 10 compounds were new. All the compounds were evaluated for antitumor activities in vitro against Hela human cervical carcinoma cell lines. Study found that all the ten compounds showed differences in their growth inhibitory effect on tumor cells. Compound with benzyl groups improved the antitumor activity. Results showed that compound 3b exhibited maximum activity against Hela cell lines at 100 μg mL^–1 (IC₅₀ value) with an inhibition rate of 70%, while the derivative 3i showed the lowest inhibitory activity (IC₅₀ <64.3 μg mL^–1).