Chlorophyllin refers to any one of a group of closely related water-soluble salts that are semi-synthetic derivatives of chlorophyll, differing in the identity of the cations associated with the anion. Its most common form is a sodium/copper derivative used as a food additive and in alternative medicine. Chlorophyll is present in green leafy vegetables and reaching levels as high as 5.7% in spinach. As a food coloring agent, copper complex chlorophyllin is known as natural green 3 and has the E number E141.