*4.3. Artichoke*

Native of the Mediterranean Basin and domesticated in Southern Italy during the Roman Empire [255,256], artichoke [*Cynara cardunculus* L. var. *scòlymus* (L.) Fiori] or globe artichoke constitutes a rich source of bioactive compounds and an important component of the Mediterranean diet to which are attributed a number of medicinal properties [20,21]. Artichoke is a major vegetable crop gaining popularity as a natural functional food. Grown on about 122,390 ha worldwide, over 1.5 million tons of artichoke heads were produced in 2017 [27]. As traditional producer and consumer of artichokes, Italy (33.1% of globe artichoke harvested area), Spain (13.4%), France (6.2%), and a few other European countries in the Mediterranean area continue to dominate the production of artichoke at global level. Nevertheless, their share is decreasing as the cultivation of this crop and its consumption are gradually expanding in other regions and reached important land investment in Egypt (10,159 ha), Algeria (5532 ha), Tunisia (3687 ha), Turkey (2994 ha), and Morocco (2923 ha) within the Mediterranean Basin, westward in Perú (8646 ha), Argentina (4472 ha), United States (2914 ha), and Chile (1464 ha), as well as eastward, especially in China (11,803 ha) that has the third largest investment on artichoke crops after Italy and Spain [27]. As a perennial crop, artichoke produces a robust stalk and large leaf biomass (about 75–80% of the above-ground plant biomass) from which during the reproductive phase the floral stems emerge sustaining the primary edible portion constituted by the immature inflorescences called heads or capitula. The capitula is constituted by a fleshy receptacle (the base of the inflorescence) with the inner heart made of tender bracts protected by more fibrous external bracts. The immature inflorescences are a rich source of macro- and microminerals, dietary fibers, inulin, vitamins, sesquiterpene lactones, and phenolic compounds including a series of flavonoids

compounds and anthocyanins that are responsible for the pigmentation of the bracts characterizing the heads of different genotypes [20,21,257,258]. The pigmentation of the heads is in fact along with other morphology parameters (shape, presence of spines on bracts) and agronomic characteristics (earliness), one of the main factors used to classify artichoke varietal types. Based on the pigmentation of the heads, artichoke landraces and new hybrids are distinguished in two groups, namely green and pigmented artichokes. The pigmentation of the heads is considered an important quality parameter affecting consumer acceptance in different regions [20,259], and often it is anticipated in the name of the varietal type especially for the pigmented varietal type like in the case of the French "Violet de Provence", "Violet de Hyères", and "Violet du Gapeau", or the Italian "Violetto di provenza", "Violetto di Sicilia", "Violetto Toscano", "Violetto di S. Erasmo", and "Violetto di Chioggia" [260]. In a recent study on the inheritance of artichoke bract pigmentation, Portis et al. [261] found a good level of heritability for bract pigmentation. However, previous studies show that there is large variations of the pigmentation of the bracts within the same landrace, and in the case of artichoke the biosynthesis and accumulation of anthocyanins is highly influenced by environmental conditions and especially by temperatures [261,262]. Artichoke pigmentation is considered a complex trait in which several metabolic pathways could be involved. In 1969, Pochard et al. [263] proposed that the anthocyanin pigmentation in artichoke could be genetically determined by one or two major genes with the involvement of several modifiers. Later, based on the segregation pattern observed in populations obtained crossing inbreed lines and clones and self-pollinated clones of different genetic origins, Cravero et al. [264] proposed that the pigmentation of artichoke heads may be controlled genetically by two independent genes P and U with a simple recessive epistasis, where plants of genotype PP or Pp allow the biosynthesis of anthocyanins and result in purple bracts whereas pp genotype inhibits anthocyanin synthesis resulting in green bracts; at the same time genotypes UU or Uu are characterized by a non-uniform pigmentation encoded by the allele P, and uu genotypes develop uniformly pigmented bracts in presence of the allele P. While further studies should confirm this simple model, the variability of the pigmentation observed within the same genotype suggests that the genetic basis for anthocyanin pigmentation of artichoke bracts is more complex and likely the two loci model proposed is regulated by several modifier genes or multiple alleles that determine the expression of the intensity of the pigmentation in artichoke heads [261,262,264]. More recently, De Palma et al. [265] isolated and functionally characterized CcF3'H as the first structural gene of the flavonoid biosynthesis (encoding for flavonoid 3'-hydroxylase) from *C. cardunculus.* While Blanco et al. [266] isolated and functionally characterized CcMYB12, the artichoke putative homologue of the transcription factor R2R3-MYBs expressing proteins that regulate the biosynthesis of flavonoids and anthocyanins in many species.

Analyzing the polyphenolic profile of artichokes in different genotypes, it is possible to identify two main classes of phenolic compounds, namely hydroxicinnamic acids (C3-C6 skeleton) and flavonoids (C6-C3-C6 skeleton). Within the first class chlorogenic, 3,5-*O*-dicaffeoylquinic, and 1,5-*O*-dicaffeoylquinic acids are the predominant compounds followed by other minor mono- and di-caffeoylquinic acids [20,21,267]. Among the flavonoids that quantitatively represent about 10% of the total phenolic compound in artichoke [20], the flavones apigenin-7-*O*-glucuronide, apigenin-7-*O*-rutinoside, apigenin-7-*O*-glucoside, luteolin-7-*O*-glucuronide, luteolin-7-*O*-rutinoside, luteolin-7-*O*-glucoside, naringenin-7-*O*-rutinoside, and naringenin-7-*O*-glucoside are the predominant compounds, followed by the anthocyanins including cyanidin, peonidin, and delphinidin derivatives [20,21,257,267,268]. Other studies have revealed that specific phenolic compounds are accumulated only in certain genotypes and certain plant portions even within the same capitula [269,270].

The first attempts to identify the anthocyanin profile of green and purple artichokes were conducted in the late 1970s [20]. However, only later Schütz et al. [271] analyzing by HPLC the pigmented bracts of seven different varietal types of artichoke isolated and identified the main anthocyanins as cyanidin 3,5-diglucoside, cyanidin 3-glucoside, cyanidin 3,5-malonyldiglucoside,

cyanidin 3-(3---malonyl)glucoside, and cyanidin 3-(6---malonyl)glucoside along with some minor compounds such as peonidin 3-glucoside, peonidin 3-(6---malonyl)glucoside, and delphinidin glycoside. The same authors observed that the anthocyanin profile varies between different genotypes, nevertheless limited information is available on the genotypic variation of these compounds in artichoke. Analyzing new hybrids and local landraces characterized by bracts with different levels of pigmentation, Bonasia et al. [272] observed that "Violetto di Provenza" and "Tempo" characterized by higher pigmentation had also the highest total phenolic content in the heart and external bracts and in the external bracts, respectively. Examining the content of total anthocyanins in bracts, leaves, and floral stems of two genotypes grown in Tunisia, namely "Violet d'Hyéres" and "Blanc d'Oran", Dabbou et al. [273] found that leaves of "Blanc d'Oran" had the highest concentration of anthocyanins (20.5 μg/g DW) while bracts and floral stems had the lowest concentration (8.3 and 5.9 μg/g DW, respectively). Instead, lower variability between different plant portions was observed in the case of "Violet d'Hyéres" that on average had a total anthocyanin concentration of 14.2 μg/g DW). These results suggest that even the leaves of artichoke plants which represent a big portion of plant biomass may constitute a good source of anthocyanins besides being a source of other phenolic compounds [274]. A very limited number of studies have been conducted to evaluate specifically the biological activity of artichoke anthocyanins [257]. The main bioactive effect attributed to anthocyanins, flavonoids, and other phenolic compounds extracted from artichoke plant tissues is their antioxidant activity demonstrated by several in vitro and in vivo studies [20,21,275,276]. Anthocyanins have also shown lipid lowering effects in a placebo-control double-blind study by reducing serum LDL cholesterol by 7.9%, triglycerides by 23.0%, apolipoprotein by 16.5%, and apolipoprotein C-III by 11.0%, and increasing HDL cholesterol by 19.4% compared with placebo after administration of 160 mg of anthocyanins for 24 weeks twice daily [277]. Intake of anthocyanins seems to have positive effects on the cardiovascular system by also reducing arterial stiffness [278]. In another study, it was observed that artichoke leaf extracts and artichoke flavonoids up-regulate the gene expression of endothelial-type nitric oxide synthase (eNOS, a vasoprotective molecule) in human endothelial cells [279]. While in a follow-up study Xia et al. [280] observed that treatment of human coronary artery smooth muscle cells (HCASMC) with artichoke leaf extracts and particularly with cynarin and cyanidin induced a down-regulation of inducible nitrous oxide synthase (iNOS, a pro-inflammatory molecule that can cause vascular dysfunctions), suggesting that artichoke flavonoid compounds may have great therapeutic potential. In recent years, a number of studies contributed to demonstrate that artichoke heads and leaf extracts and, in some cases, specific phenolic compounds have health-beneficial properties including anti-inflammatory activity, anti-bacterial activity, hepatoprotective activity, hypocholesterolemic and low density lipoproteins (LDL) oxidation inhibition effect, hypoglycemic effect, as well as anticancer activity [20,21,257]. Nevertheless, in most of the cases these biological activities cannot be attributed to a single compound, but are determined by the combined synergistic effect of different compounds [20,21]. In this perspective, the matrix effect is fundamental in determining the bioaccessibility, bioavailability, and the effect of polyphenols, especially considering that polyphenols and anthocyanins in particular have a relatively low bioavailability being quickly transformed into derivatives of phenolic acids [21,281–283].
