ADA and cancer: In the present study, we describe for the first time, the anti-cancer properties of ADA, a naturally occurring H2S donor, isolated and purified from Ferula assa-foetida L. Sulfur compounds contained within vegetables may be chemically or enzymatically transformed in the human body with subsequent formation of H2S (Jacob et al., 2008) and their consumption has been associated to chemopreventive effects (Krasilnikov et al., 2003).