Gymnemic acids are glycosides isolated from the leaves of Gymnema sylvestre (Asclepiadaceae). Gymnemic acids like ziziphin and hodulcine are anti-sweet compounds, or sweetness inhibitors. After chewing the leaves, solutions sweetened with sucrose taste like water. More than 20 homologues of gymnemic acid are found in the leaves. Gymnemic acid I has the highest anti-sweet properties. It suppresses the sweetness of most of the sweeteners including intense artificial sweeteners such as aspartame and natural sweeteners such as thaumatin, a sweet protein. The anti-sweet activity is reversible, but sweetness recovery on the tongue can take more than 10 minutes.