FTIR microspectroscopy discriminates anticancer action on human leukemic cells by extracts of Pinus kesiya; Cratoxylum formosum ssp. pruniflorum and melphalan

► FTIR microscopy distinguished the anticancer mode of action of the test compounds against U937 cells, with the most effective being melphalan, followed by Pinus kesiya and Cratoxylum formosum extracts. ► All compounds raised the intensity of the β-pleated sheet higher than that of the control with the shift of α-helix band and alteration of the secondary structure of the protein band. ► The difference in IR intensity associated with lipids, proteins and nucleic acids were responsible for discrimination of the anticancer mode of action of each compound.