Phenolic Compounds
Thousands of phenolic
compounds have been characterised from plant based foods.
Phenolic compounds such as
anthocyanins, flavonols, hydroxycinnamates and ellagitannins are found in
abundance in berries. These compounds are not considered to be nutrients
but recent research has shown that they are powerful
antioxidants and therefore could help to protect against free radical
damage.
Anthocyanins
The predominating group of flavonoids in many types of berry are the
anthocyanins. They are responsible for the red, blue and purple colours of
berries and their phenolic structure conveys a high antioxidant activity in
vitro. Each type of berry varies in it's amount and composition of anthocyanins,
for example the main types of anthocyanin in strawberry are pelargonidins, in
blackcurrant delphinidins and cyanindins can be found, and in raspberry,
cyanidins are the main form.
Anthocyanins may be protective against heart disease as they have been shown to
prevent oxidative damage to human low density lipoproteins (LDL). Oxidation of
LDL is thought to be a key step in the formation of heart disease.
Flavonols
Flavonols are another type of flavonoid found in berries, for example quercetin
glycosides. These compounds also have antioxidant
activity. Quercetin has been shown to inhibit LDL oxidation and protect DNA from
oxidative damage. Quercetin has also been shown to inhibit enzymes involved in
the inflammatory response, inhibit growth of cancer cells in vitro and reduce
tumour incidence and multiplicity in animals.
Ellagitannins
The major contributors to ellagitannin intake in western diets are fruits such
as strawberries, raspberries and blackberries. Extensive research has been
carried out on the anti-cancer properties of ellagic acid, the hydrolysis
product of ellagitannin. This compound may be able to help the body to defend
against free radicals, stimulate defence enzymes to detoxify cancer causing
chemicals and help regulate the cell cycle and cell death in cancer cells. Other
research has found that a proportion of ellagitannins may escape absorption and
therefore could have beneficial effects in the colon.
