**2. Grapevine phenolic compounds**

Phenolic Compounds in grapes account for only a trivial proportion of the berry weight but contribute significantly to fresh fruit. All phenolic compounds have some common features as; an "aromatic ring" comprising of six carbon atoms having one or more hydroxyl (OH) groups or their derivatives as indicated in **Table 1**. They play an important role in color development, astringency, flavor and aroma to grapes. These compounds are the main substrates for grape juice and wine oxidation [16–18]. Their susceptibility to oxidation due to unsaturated double bonds and hydroxyl groups make phenolic compounds valuable antioxidants [19, 20]. Flavonoids and non-flavonoids phenolics are produced inside grape berries through biochemical pathway (**Figure 1**). Flavonoids accumulate mainly in the skin, seeds, and stem while neoflavanoids mostly accumulate in the mesocarp of the berry.

Phenolic profile of grapevines depends on, region, prevailing weather conditions, and site-specific viticultural practices [22–28]. Higher the total phenolic content more is antioxidant activity and it is a genotypic character [29–32]. Skin color (yellow, pink, red, blue-black and full black) is due to presence of anthocyanins. Anthocyanins are synthesized to protect the berries from the negative effect of adverse environmental conditions particularly ultraviolet radiation. Accumulation and degradation of already synthesized anthocyanins was noticed due to elevated temperatures during


### *Effect of Climate Change on Polyphenols Accumulation in Grapevine DOI: http://dx.doi.org/10.5772/intechopen.99779*

#### **Table 1.**

*Different classes of polyphenolic compounds and their basic structures along with examples are given.*

#### **Figure 1.**

*Shikimate pathway for the biosynthesis of anthocyanins, Flavonols and flavonoids. (reproduced from the idea of Velasco et al. [21] with few modifications).*

the ripening period [33, 34]. Therefore, in hotter regions the anthocyanin in red and black grapes skin is affected more, while climatic conditions in colder growing regions favor their biosynthesis. Grapevine varieties (var.) have particular anthocyanin fingerprints e.g., malvidin-3-Oglycoside is most abundant in var. 'Hasansky Sladky' while in var. 'Zilga' it is delphinidin-3-O-glycoside. Moreover, their biosynthesis varies from year to year due to annual seasonal climatic variability [35].

*Effect of Climate Change on Polyphenols Accumulation in Grapevine DOI: http://dx.doi.org/10.5772/intechopen.99779*

**Figure 2.**

*Acetate Mevalnoate pathway for monoterpenoids biosynthesis. (reproduced from the idea of Velasco et al. [21] with few modifications).*

#### **2.1 Phenolic compounds biosynthesis in grapevine**

Production of phenoloic compounds is regulated by transcription factors which regulate the activity of genes involved in phenolic biosynthetic pathways. Moreover, location, timing, and extent of the production of phenolic compounds is also dependent on these transcription factors [36, 37]. In addition to grape berries, some flavonoids are produced in leaves and are imported via the phloem [38, 39]. Shikimate and malonate pathways are the two main "assembly lines". The shikimate pathway (**Figure 1**) is the part of the biosynthesis chain of most plant phenolics, whereas the malonate pathway (**Figure 2**) is less important compared with Shikimate pathway in plants, but the malonate pathway is essential in fungi and bacteria.
