An organic polysulfide compound found in garlic that acts as an H2S donor; reduces the survival of prostate cancer PC-3 cells (IC50 = 22 μM) and inhibits the growth of human colon adenocarcinoma HCT15 cells (IC50 = 11.5 μM); suppresses the growth of PC-3 xenografts in vivo in mice and induces vascular smooth muscle relaxation.