**3. Phytonutrients and their applications**

Natural products and their derivatives have played a significant role in medicine, generating many of the first new molecular entities (NMEs) and nearly half of all approved NMEs [36].

Scientific research is more and more focused on identifying biologically active food components that can optimize physical and mental well-being and reduce the risk of disease onset. Nutraceuticals or phytonutrients are products of natural origin, foods, or parts of them, that promote good health, longevity, and quality of life and, what is more, they can be used, in some cases, for the prevention and even treatment of chronic diseases.

Phytonutrients include the polyphenols. Polyphenols and their derivatives are widely distributed bioactive compounds in plant-derived foods (fruits, vegetables, legumes, cereals, seeds, spices, wine, tea, coffee, cocoa, and herbs) [37]. These bioactive compounds have received considerable interest over the past decade because of their wide range of biological activities. They are a broad group of compounds organic, plant secondary metabolites. The polyphenolic composition of plants is highly variable, both qualitatively and quantitatively; some of them are ubiquitous, while others are restricted to specific families or species [38]. From a structural point of view, polyphenols are compounds with one or more hydroxyl groups, associated with the aromatic ring, which can be present either in the oxidized form (quinone) or in the reduced form (phenol). Depending on the number of phenolic rings (hence the name "polyphenols") and the structural elements attached to them, polyphenols can be distinguished into flavonoids and non-flavonoids (phenolic acids, stilbenes, and lignans) [39]. Currently, about 8000 different structures of plant phenols are found. Flavonoids, in turn, are divided into six main subclasses: isoflavones, flavones, flavonols, anthocyanins, flavanones, flavanols. They are usually associated with a sugar, forming glycosides [40].

Here, in detail, we will review the activity of two polyphenols in neurodegenerative retinal diseases related to Zika virus infection.

## **3.1 Resveratrol**

Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a plant-derived substance that is a member of the stilbenes group, non-flavonoid compounds belonging to the polyphenol family (**Figure 6**). Stilbenes are produced by the combination of the acetate and shikimate pathway.

**Figure 6.** *Resveratrol structure.*

Resveratrol is naturally found in the two isomeric forms cis and especially in the trans, which shows greater activity biological activity [41].

The most abundant dietary source of resveratrol is red grapes. Discrete amounts are also found in blueberries, berries, and the polygonum cuspidatum plant.

Resveratrol has been shown to have a powerful antioxidant action. In fact, the presence of this substance in red wine is associated with the benefits obtained by populations that habitually consume it in their diets. The cardioprotective properties of resveratrol are well known, and the presence of this compound in red wine is partly responsible for the phenomenon known as the "French Paradox". In France, habitual consumption of red wine reduces the incidence of mortality from cardiovascular disease. It is also known to have anti-inflammatory, anticancer, protective properties on nerve cells, antiaggregant, immunomodulatory, antibacterial, and antifungal properties of resveratrol. All these activities are due to the interaction of this molecule with several cellular synthetic pathways involving enzymes such as cyclooxygenase, lipoxygenase, and tyrosine kinase.

## **3.2 Hesperidin**

Hesperidin (4′-methoxy-7-O-rutinosyl-3′,5-dihydroxyflavanone; hesperetin 7-O-rutinoside) is a naturally occurring flavanone glycoside found in citrus fruits (most notoriously oranges) and is a sugar-bound form of the flavonoid hesperitin (**Figure 7**) [42].

Flavanones, also called dihydroflavones, have a saturated C ring and can be multi-hydroxylated; in addition, several hydroxyl groups can be methylated and/or glycosylated [43].

**Figure 7.** *Hesperidin structure.*

*Nutraceutical Approach for the Treatment of Retinal Inflammation after Infections DOI: http://dx.doi.org/10.5772/intechopen.105687*

Hesperitin is known to mediate the actions of hesperidin in the body, and since hesperidin needs to progress to the colon to be "released" by intestinal bacteria, it acts as a time release for hesperitin; one serving of hesperidin seems to increase blood levels for over the course of a day or so when consumed in this manner.

Various biological and pharmacological effects have been reported for hesperidin. It possesses the antioxidant, anti-inflammatory, and anti-carcinogenic activities [44]. Hesperidin possesses also considerable neuroprotective property in various neurodegenerative diseases, such as Alzheimer's, Parkinson's, stroke, and Huntington's [45].
