Low doses of partially purified fraction of kaffir lime (Citrus hystrix DC.) leaf extract induce cell death in Molt4 cells

Introduction: Kaffir lime ( Citrus hystrix DC.) is a medicinal plant found in Southeast Asia, both fruit and leaf have been used in Thai traditional medicine and food recipes. Objectives: Previous report demonstrated that partially purified fraction F9 of kaffir lime has anti-leukemic activity. This study aimed to investigate the anti-proliferative effects of low doses of F9 in Molt4 (human acute lymphoblastic leukemia) cell line. Effects on cell cycle progression as well as cell cycle regulatory proteins at the related phases after treatment were also studied. Materials and methods: Cytotoxic effect of F9 was studied by MTT assay, and its effect on cell cycle progression in Molt4 cells was further examined by flow cytometry. The effect on regulatory proteins was determined by Western blot analysis. Results: The F9 showed cytotoxic activity with an IC50 value of 24.5 μg/mL and low dose at the concentration of IC20 (2.5 μg/mL) of F9 induced cell death (sub-G1) as analyzed by flow cytometry. The F9 also increased p53 level while decreased cyclin A, cyclin B, and cdc2 (regulatory proteins in S and G2/M phases) protein expressions in a time- and dose-dependent manner. Conclusion: The F9 from kaffir lime leaf at low doses induced cell death. Moreover, it also inhibited cell cycle regulatory proteins. This new knowledge will be further investigated to determine active compounds in the future.