The dried skins of grapes (Vitus vinifera) are used in various supplemental products. Containing much of the color of the grape, the skins have many flavonoids called anthocyanins. Flavonoids such as anthocyanins were at one time called "Vitamin P" because they were thought to be necessary and even able to substitute for vitamin C. While this turned out not to be true, the ability of these flavonoid compounds to enhance and synergize with vitamin C is now well established. While grape seed and whole grape extracts are now more popular for these uses, grape skins are still of great use when combined with vitamin C containing botanicals or ascorbic acid.