Prevalence and Functions of Anthocyanins in Fruits

Abstract

This chapter reviews possible visual, nutritional and physiological functions of anthocyanins in fruits. Merits of the various functions are considered and discussed with reference to the prevalence of different fruit colours and the contribution of anthocyanins thereto as well as anthocyanin accumulation in response to environmental factors, seed disperser visual systems and fruit quality parameters. Blue, purple, black and most red fruits derive their colour from anthocyanin accumulating during ripening. Red and black are the most common colours of small bird-consumed fruits whereas larger ‘‘mammalian’’ fruits are more typically orange, brown or green in colour. Red fruits are conspicuous to birds with their tetrachromatic vision, but cryptic to unintended dichromatic mammalian frugivores and opportunistic insect seed predators. Blue fruits are scarce, probably because they are easy to detect by disadvantageous frugivores. Black fruits, with their very high anthocyanin levels, are fairly common despite being inconspicuous to dispersers. The prevalence of black fruits could relate to the powerful antioxidant ability of anthocyanins. On the other hand, blackness also correlates with fruit maturity and, thus, quality. Finally, the presence of anthocyanins in immature fruits and its regulation by environmental factors could relate to the photoprotective ability of anthocyanins. Since anthocyanins are able to fulfil a range of functions in plants, their adaptive value in fruits should be interpreted against a background of interaction with dispersers, genotype and environment.