*3.3. Pepper*

Pepper (*Capsicum* spp.) is one of the oldest domesticated and utilized crops and the genus *Capsicum* consists of approximately 31 species of which the five domesticated species are *C. annuum*, *C. baccatum*, *C. chinense*, *C. frutescens*, and *C. pubescen* [193]. Average world production and cultivated area of dry and green peppers are estimated at 3.9 and 34.5 million tons respectively, harvested from 1.8 and 1.9 million hectares respectively [27]. Pepper fruit have high nutritive value, as they are rich in vitamin C (ascorbic acid), provitamin A (β-carotene), vitamin E (tocopherols), flavonoids and capsaicinoids, and other carotenoid pigments such as lycopene and zeaxanthin [194]. The noticeable level of phenolic compounds and carotenoid pigments also contributes to the antioxidant properties of sweet pepper [195].

Immature fruits are usually colored in white, green, purple, and black shades and gradually color changes to yellow, orange, red and brown as fruit maturity advances [196,197]. The differences in fruit color is mainly due to the differential accumulation of flavonoids and carotenoids [198]. Anthocyanin accumulation in the outer epidermis of immature pepper fruit is responsible for the purple or black color at 30 d after anthesis [199] and turns to red color at 50 d after anthesis [182].

Liu et al. [182] compared the flavonoids biosynthesis at 30 d after anthesis for green, white, and purple varieties, and reported that anthocyanins, flavones, and flavonols content was significantly higher in purple variety than in the other varieties, with delphinidin, luteolin, chrysoeriol and quercetin derivatives being the most abundant polyphenols. Delphinidin, cyanidin, and malvidin derivatives were the major anthocyanins in colored peppers among the 16 anthocyanins detected of which delphinidin 3,5-diglucoside and delphinidin 3-*O*-rutinoside were specifically accumulated in purple peppers [182]. In the same study, it was reported that the purple color of fruit is related to the high accumulation of cyanidin and delphinidin derivatives at 30 d after anthesis.

In chili peppers, anthocyanins' presence and pigmentation of purple or black and magenta is also possible, and is usually found in flowers, fruit, and foliage [200]. Several reports highlighted the presence of anthocyanins in chili pepper fruit, but so far delphinidin is the only anthocyanidin identified [200,201]. Similarly, Sadilova et al. [181] reported delphinidin-3-*trans*-coumaroylrutinoside-5-glucoside (nasunin 89%) and delphinidin-3-*cis* coumaroylrutinoside-5-glucoside (4.6%) as the main anthocyanins (averaged

at 320 μg/g fw) in German chili pepper (*C. annuum* L.), while similar results were found in two Mexican chili peppers [202]. Moreover, hydroponically grown dark violet pepper (cv. "Zorro") had the highest concentration of quercetin and catechin when compared to orange, red and yellow fruit cultivars [203].

Capsanthin-capsorubin synthase (CCS), as a unique enzyme in pepper and tiger lily, converts antheraxanthin and violaxanthin into capsanthin and capsorubin, respectively [204]. Although the exact mechanism is under investigation, Liu et al. [182] reported that the highly active CCS drives antheraxanthin to be converted into capsanthin in purple fruit, which reduces the flux to violaxanthin, eventually resulting in significantly lower levels of antheraxanthin and violaxanthin in purple than in green and white fruit varieties.
