**2. Chemical structure**

Plants that belong to the subgenus *Rubus* spp. are typical wild species and are usually hand‐ picked in the season. However, since it became an important plant for agriculture, there has been an increasing interest in improving the size of the fruit, the organoleptic properties, fruit yield, and get rid of the thorns, since they constitute a nuisance for harvest. To achieve these objectives, classic crossbreeding has resulted in development of many commercial varieties to favor a given trait that benefits production in each geographical location. Among these cultivars are "Ashton Cross" that is vigorous and thorny, "Bedford Giant" that in addition to these two traits shows a good yield; "Black satin," also vigorous but thornless; "thornless evergreen" that provides a thornless plant, high yield and high quality fruits; "Fantasia" that produces very large fruits and finally in this shortlisted group is "Loch Ness," that is a thorn‐ less cultivar with very large fruits and semierect canes, which is the cultivar used in this study

*Rubus* spp. Var. Loch Ness is a high yielding thornless tetraploid (4*n* = 28) blackberry, and one of the most widely cultivated varieties. However, despite its high-added economic value and as a source of bioactive compounds, its genome has not been sequenced yet. Therefore, other strategies need to be used to gain knowledge of the production and health-related benefits.

The aim of this chapter is to review the literature about blackberry and report the state of the arts about this plant species. As the genome is not reported, data about the core genes in the biosynthetic pathway as well as regulatory genes are referred to as the model plant *A. thaliana*. Also, structure of the bioactives which is responsible for health benefits as well

**cyanidin/100g FW)**

Early Wilson 64.76 ± 23.68 3.21 ± 0.38 Gazda 27.97 ± 13.71 6.52 ± 0.82 Lesniczanka 96.63 ± 32.18 5.36 ± 0.45 Zagroda 143.66 ± 52.59 4.98 ± 0.52

Black Satin 175.52 ± 53.97 1.58 ± 0.31 Chester Thornless 200.34 ± 65.58 3.68 ± 0.46 Hull Thornless 105.39 ± 31.08 0.82 ± 0.35 Loch Ness 220.11 ± 81.07 2.39 ± 0.28 Orkan 142.42 ± 44.01 2.26 ± 0.25 Smoothstern 186.55 ± 58.94 2.32 ± 0.33 Tayberry 177.84 ± 56.20 1.7 ± 0.32 Thornless 147.46 ± 44.02 1.07 ± 0.33

**Flavonols (mg eq catechin/100g FW)**

**Variety Anthocyanins (mg eq** 

Thorny Darrow 99.33 ± 48.32 4.23 ± 0.48

Thornless Black Beaty 179.46 ± 57.84 3.06 ± 0.40

**Table 2.** Phenolic compound contents of thorny and thornless blackberries (mg/100g FW) [13].

(**Table 2**) [12].

132 Flavonoids - From Biosynthesis to Human Health

Flavonols, anthocyanins, and catechins are molecules belonging to a wider group of second‐ ary metabolites, the flavonoids. Flavonoids represent a large subgroup of a phenolic class of plant specialized metabolites, which are found in almost every plant in the nature. The basic flavan skeleton that forms all flavonoids is a 15-carbon phenylpropanoid core (C6-C3-C6 system), which is arranged into two aromatic rings (A and B) linked by a heterocyclic pyran ring (C). They are characterized by the presence of a double bond between C-2 and C-3, and the attachment of the B ring to C-2. According to the oxidation status and saturation of the heterocyclic ring, flavonoids are categorized into flavonols, flavones, catechins, flavanones, anthocyanins, and isoflavonoids [1]. The most abundant compounds present in blackberry (also in berries) are flavonols, anthocyanins, and catechins (**Figure 2**).


**Figure 2.** Flavonol, anthocyanin, and catechin molecular structures and common substituents.

Flavonols have a 3-hydroxyflavone (IUPAC name: 3-hydroxy-2-phenylchromen-4-one) as the main structure. The diversity of these compounds is derived from the different positions of the hydroxyl groups of the phenolic ring that are usually glycosylated and can undergo fur‐ ther modifications like acylations; in this group, the three main families are derived from kaempferol (4′OH), quercetin (3′, 4′, 5′OH) and rutin (3′, 4′OH).

Anthocyanins are mainly glycosylated as well, being the aglycon the anthocyanin molecule. The chemical structure of this aglycone is the flavylium ion (2-phenyl-benzopirilo) that has a benzopyran aromatic ring, and a phenolic ring. There are six different families within this group, namely cyanidin, pelargonidin, delphinidin, malvinidin, peonidin, and petunidin. As in the case of flavonoids, the greatest source of chemical diversity is the number and position of sugars for glycosylation. Acylation is another main biochemical mechanism leading to diverse anthocyanin molecules in *Arabidopsis* [14, 15]. Up to date, several enzymes have been character‐ ized to catalyze these acylation reactions, using either malonyl-CoA or *p*-coumaroyl-CoA as substrates to transfer the malonyl or *p*‐coumaroyl groups to cyanin structures [16]. Diversity can be further increased transferring sinapoyl groups to cyanins to form sinapoylated cyanins [17].

Catechins have two benzene rings (A-, B-) and a dihydropyran heterocyclic ring (C) with a hydroxyl group over carbon 3. As a result of this structure, catechins have four diasteroiso‐ mers, two with *trans* configuration called catechin ((+)-catechin and (−)-catechin), and two with *cis* configuration called epicatechin ((+)-epicatechin and (−)-epicatechin). These catechins can further polymerize to form proanthocyanins, in which the diversity of structures relies on the number of monomers that polymerize and the type of bonds that stabilize them.
