Anthocyanins (from Greek: ἄνθος (anthos) = flower + κύανος (kyanos) = blue) are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH. They belong to a parent class of molecules called flavonoids synthesized via the phenylpropanoid pathway; they are odorless and nearly flavorless, contributing to taste as a moderately astringent sensation. Anthocyanins occur in all tissues of higher plants, including leaves, stems, roots, flowers, and fruits.
Anthocyanins are the colorful flavonoids concentrated in brightly colored berries and fruit ("anthos" means "flower" and "cyan" means "blue") being most concentrated in bilberries, blueberries, cranberries, elderberries, purple grapes, red wine and hawthorn berries.
Anthocyanin extracts are important for the health of the micro-blood vessel network and are clinically used in this way by medical herbalists and physicians in mainland Europe. Recent studies in the United Kingdom confirm that anthocyanins facilitate the repair of vessel damage responsible for 'small blood vessel permeability' and the related fluid retention caused, including swollen limbs, fingers, breasts and the tissue surrounding the eye area. There is currently little orthodox treatment for this type of fluid retention except diuretics, which are not without side effects and fail to address the underlying cause of the disorder. The ancestral diet was replete with anthocyanins and these antioxidants help to protect the body from harmful free radicals. Bilberry anthocyanins can act to quickly repair and regenerate broken and leaky capillaries and blood vessels within the body. Anthocyanins are also powerful antioxidants that help to protect skin against U.V. rays. Anthocyanins bind to and stabilize collagen and elastin; they stabilize the phospholipids of endothelial cells and increase synthesis of collagen and mucopolysaccharides, which give the arterial walls structural integrity. This strengthening activity could be critical for preventing strokes and cancer. Also, the increased production of collagen and elastin by cells reduces inflammation, which can be beneficial in the treatment of arthritis and asthma. European doctors routinely prescribe anthocyanin extracts before operations to prevent excessive post-operative bleeding. Improved circulation also brings enhanced mental clarity as well. It is well recognized that cranberry and blueberry anthocyanins can effectively treat and prevent mild chronic and recurrent bladder and urinary tract infections; they act to prevent bacteria from adhering to urinary tract walls.
Anthocyanins tend to be the main polyphenolics in red grapes whereas flavan-3-ols (e.g., catechins) are the more abundant phenolic in white varieties. Total phenolic content, an index of dietary antioxidant strength, is higher in red varieties due almost entirely to anthocyanin density in red grape skin compared to absence of anthocyanins in white grape skin. It is these anthocyanins that are attracting the efforts of scientists to define their properties for human health.