Increasing attention has been paid by consumers to the health and nutritional aspects of horticultural products. Fruits and vegetables contain significant levels of biologically active components that positively impact health beyond basic nutrients. High consumption of fruits and vegetables has been associated with decreasing the risk of several chronic diseases caused by oxidative stress.
Berry fruits are a good source of natural antioxidant substances such as anthocyanins, flavonoids, and phenolic acids and have high antioxidant enzymes and oxygen radical scavenging activities which could act effectively as free radical inhibitors and provide protection against harmful damage.
Many phenolic compounds important to our diets, such as hydroxybenzolic and hydroxycinnamic acid derivatives, anthocyanins, flavonol glycosides, flavan-3-ols, and proanthocyanidins are abundant in berry fruits. Positive correlations have also been found between oxygen radical absorbance capacity (ORAC) and anthocyanin or phenolic content in various berries.
Some phytochemicals have exhibited additive and synergistic effects on antioxidant activity when they were combined in different concentrations. This ability of antioxidant compounds to reinforce each other can have a significant effect on the antioxidant responses and their correlations. Research also indicates better health functionality of whole foods compared to single active compounds suggesting a synergistic interaction of phenolic phytochemicals in the diet.
Antioxidant activities are positively correlated to antioxidant enzyme activities. Antioxidant enzymes include superoxide dismutatse (SOD), peroxidase (POD), catalase (CAT), and glutathione peroxidase (GSH-POD) among others. The main function of these antioxidant enzymes is to neutralize free radicals.
Antioxidant enzymes may stop free radical formation in the first place or interrupt an oxidizing chain reaction to minimize the damage caused by free radicals. The risk of free radical-related health problems could be reduced by decreasing exposure to free radicals and increasing the intake of antioxidants and antioxidant enzyme rich foods.
There is a wide diversity of phytochemical levels and antioxidant capacities within and across genera of small fruits. Increasing evidence suggests that genotype has a profound influence on nutritional quality and the content of bioactive compounds in berries. Besides genotype variation, fruit maturation, preharvest conditions and postharvest handling could all affect antioxidant profiles and their activities.
It is well known that levels of phenolics and antioxidant capacity of berry fruits vary greatly among cultivars. There are wide differences in their components and their activities within and across genera of berry fruits. Genotype and species of berry fruits have a profound influence on the content of bioactive compounds. Different berry crops contain different major phenolic compounds and anthocyanins.
Anthocyanins and phenolics are secondary plant metabolites. They protect the plant against damaging photodynamic reactions by quenching the excited state of active oxygen species. A linear correlation exists between total phenolic content and ORAC activity for fruits of blackberry, raspberry, and strawberry.
In raspberries, the antioxidant capacity also appears to be directly related to the total phenolic content. in raspberries, blackberries, red currants, and gooseberries, the FRAP values were highly correlated with phenolic content (r = 0.95), whereas a less linear correlation between total antioxidant capacity and anthocyanin content was recorded (r = 0.64). Wild berries have significantly higher antioxidant activities and phenolic content than domestic berries.
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