The combination of curcumin and ursolic acid (from apple peels) shrank prostate tumors in mice by inhibiting the tumor from metabolizing glutamine.

The combination of ursolic acid and resveratrol (from grape skin) also shrank the prostate tumors in mice. Many different tumor types rely on glutamine as a carbon source for energy and as a nitrogen source for building more DNA and proteins (macromolecular synthesis). Additionally, these compounds also activated pathways involved in cell death.