The term flavonoid denotes a large group of chemical compounds. Flavonoids contain a C6-C3-C6 carbon skeleton with sugar moity (in glucosides).
There are indications that flavonoids have a useful protective action, in particular against some respiratory disease.
It also has been implicated that a high intake of flavonoids reduces the risk of cancer.
The greatest contributors of flavonoids in human diets are fruits and vegetables with fruit juice, green tea, and dark chocolate being the richest sources in western diets.
They are four main types of flavonoids in fruit:
Flavonol
For example quercetin glycosides in apple, plum and grape. The consumption of flavonoids has been estimated to average 190 mg/day in the US mostly as flavonols.
Anthocyanins
Red and blue pigments such as cyaniding and delphinidin and their glycosides
Flavones
Luteolin in lemon peel
Flavanones
For example, hesperidins in oranges and naringin in grapefruit. The cloudiness of juice and marmalade made from oranges is due to precipitation of hesperidins, which is less soluble in water.
Naringin has a bitter taste and is soluble in water, some fresh grapefruits and pumelos taste slightly bitter.
Flavonoids in fruit
