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

Apoptosis is the principal molecular goal of chemotherapeutics for effective anticancer action. We studied the effect of 50% ethanolic-water extracts of Pinus kesiya, Cratoxylum formosum ssp. pruniflorum and melphalan on cytotoxicity and apoptosis induction for human leukemic U937 cells, and explored the mode of action using FTIR microspectroscopy. The number of viable U937 cells in vitro was decreased in a concentration-dependent manner by all tested compounds, although potency differed between the U937 and Vero cells. Melphalan and the extract of C. formosum exhibited relatively lower IC50 values (15.0 ± 1.0 and 82.7 ± 3.2 μg/mL respectively) and higher selectivity (selective index > 3) than the extract of P. kesiya (299.0 ± 5.2 μg/mL; selective index < 3) on the U937 cells. All three compounds significantly induced apoptosis through the late stage – seen by the indicative DNA ladder – with the most effective being melphalan, then the P. kesiya and C. formosum extracts. FTIR microspectroscopy revealed that all three compounds raised the intensity of the β-pleated sheet – higher than that of the untreated U937 cells – corresponding to a shift in the α-helix band associated with an alteration in the secondary structure of the protein band, confirming induction of apoptosis via pro-apoptotic proteins. The differences in intensity of the FTIR bands associated with lipids, proteins and nucleic acids were responsible for discrimination of the anticancer mode of action of each of the three compounds. The FTIR data suggest that the two plant extracts possessed anticancer activity with a different mode of action than melphalan.