The present invention relates to a method of making a powder from apple peel by providing an apple peel, subjecting the apple peel to a phytochemical preservation treatment, drying the treated apple peel, and grinding the dried, treated apple peel to a powder. A powder from apple peel having a phenolic content and a flavonoid content similar to fresh apple peel on a fresh weight basis, where the powder has a water activity of less than 0.30 is also disclosed. The present invention also relates to a method of treating cancer in a patient by administering a powder from apple peel to a patient under conditions effective to treat cancer. Also disclosed is a method of inhibiting proliferation of cancer cells by contacting cancer cells with a powder from apple peel under conditions effective to inhibit proliferation of the cancer cells.
