A Cytotoxic Principle of Tamarindus indica, Di-n-butyl Malate and the Structure-Activity Relationship of Its Analogues

Bioassay-guided fractionation of the methanolic extract of Tamarindus indica fruits led to the isolation of l-(-)-di-/n-butyl malate which exhibited a pronounced cytotoxic activity against sea urchin embryo cells. In order to study structure-activity relationships, close-structure relatives of di-n-butyl malate were synthesized using d-(+)- and l-(-)-malic acid as starting materials, and their cytotoxic activities were examined for the sea urchin embryo assay. l-(-)-Di-n-pentyl malate was the most effective inhibitor to the development of the fertilized eggs. Significant inhibitory activity was not seen in the esters of d-(-)-isomer.