Allicin Purified From Fresh Garlic Cloves Induces Apoptosis in Colon Cancer Cells Via Nrf2

Abstract

Allicin (diallyl thiosulfinate) is the best-known biologically active component in freshly crushed garlic extract. We developed a novel, simple method to isolate active allicin, which yielded a stable compound in aqueous solution amenable for use in in vitro and in vivo studies. We focused on the in vitro effects of allicin on cell proliferation of colon cancer cell lines HCT-116, LS174T, HT-29, and Caco-2 and assessed the underlying mechanisms. This allicin preparation exerted a time- and dose-dependent cytostatic effect on these cells at concentrations ranging from 6.2 to 310 μM. Treatment with allicin resulted in HCT-116 apoptotic cell death as demonstrated by enhanced hypodiploid DNA content, decreased levels of B-cell non-Hodgkin lymphoma-2 (Bcl-2), increased levels of bax and increased capability of releasing cytochrome c from mitochondria to the cytosol. Allicin also induced translocation of NF-E2-related factor-2 (Nrf2) to the nuclei of HCT-116 cells. Luciferase reporter gene assay showed that allicin induces Nrf2-mediated luciferase transactivation activity. SiRNA knock down of Nrf2 significantly affected the capacity of allicin to inhibit HCT-116 proliferation. These results suggest that Nrf2 mediates the allicin-induced apoptotic death of colon cancer cells.

ACKNOWLEDGMENTS

This study was partially supported by an internal grant program from The Robert H. Smith Faculty of Agriculture, Food, and Environment, The Hebrew University of Jerusalem. We declare that we have no conflict of interests. W. Bat-Hen, a student, performed experiments of cell culture, and isolation of allicin. G. Tal, a student, helped with allicin isolation and HPLC measurements, I. Peri helped with experimental design, Z. Ludmer conceived the novel isolation procedure of allicin and helped to draft the manuscript, and B. Schwartz was in charge of the design of the study and its coordination, performed the statistical analyses, and was in charge of the draft of the article. All authors read and approved the final manuscript.