Anthocyanin

Anthocyanins are water-soluble pigments that belong to the flavonoid group of phytochemicals. They are the glycosides of anthocyanidins and are responsible for the red, purple, and blue colors found in many fruits, vegetables, and flowers. Common anthocyanidins include cyanidin, delphinidin, pelargonidin, petunidin, peonidin, and malvidin, with sugars such as glucose, galactose, or rhamnose forming the anthocyanin molecules. Many anthocyanins are also acylated with aromatic acids, which can affect color and stability.

Anthocyanins occur in the vacuoles of plant cells and accumulate in tissues such as berries, grapes, red cabbage, purple corn, and red onions. They contribute to attracting pollinators and seed dispersers, as well as providing photoprotection and stress responses in plants. Their color is influenced by pH, co-pigmentation, metal ions, and chemical structure, leading to red in acidic environments and blue in more basic conditions.

Biosynthesis of anthocyanins proceeds via the plant phenylpropanoid and flavonoid pathways, beginning with phenylalanine. They play ecological roles in plant signaling and protection, and in human use they are valued as dietary antioxidants and as natural colorants. Their stability is pH-dependent and they are sensitive to heat, light, and oxygen, which can lead to fading during processing or storage. They are used as natural food colorants (often labeled as E163) and are studied for potential health effects, though clinical evidence of clear therapeutic benefits remains inconclusive.

Measurement of anthocyanins in foods typically reports total content in equivalents of a reference compound, such as cyanidin-3-glucoside, to enable comparison across samples.