## 2 Bioactive Compounds Commonly Found in Green-Colored Fruits and Vegetables
### Terpenoides  
Tetraterpenoids/Carotennoids: Cryptoxanthin, Lutein, and Zexanthin  
General Characteristics, Structure, and Food Sources  
Cryptoxanthin, also known as \(\beta\)-cryptoxanthin, is a natural pigment that imparts bright colors to vegetables and fruits. It is an oxidized carotenoid containing hydroxyl and other oxygen groups. It belongs to the lutein group and is yellow-orange in solution and free state. Its molecular formula is C\({}_{40}\)H\({}_{56}\)O, and its relative molecular weight is 552.88 g/mol (Table 2). Cryptoxanthin is widely found in oranges, papaya, persimmon, avocado, graprefruit, red bell pepper, coriander, pumpkin, corn, leafy vegetables, and some yellow animal foods, such as egg yolks and butter [81]. It is a major dietary provitamin A carotenoid mostly provided by citrus fruits. Lutein and zexanthin belong to the family of oxygenated carotenoids classified as xanthophylls, which are found in high quantities in green leafy vegetables and fruits, such as avocado, kale, parsley, spinach, broccoli, green peas, green beans, kiwi, green lettuce, cucumber, green pepper, celery, green grapes, brussels sprouts, scallions, watercress,romaine lettuce, and zucchini (Table 1) [82,83]. Lutein and its isomer zeaxanthin are the dihydroxy derivatives of \(\alpha\)-carotene and \(\beta\)-carotene, respectively [84]. They are termed macular pigments. Lutein (C\({}_{40}\)H\({}_{56}\)O\({}_{2}\)) is a lipid-soluble molecule with a melting point of 190 \({}^{\circ}\)C and a molecular mass of 568.87 g/mol (Table 2). In addition, lutein contains several secondary metabolite compounds such as steroid/triterpenoid, alkaloid, flavonoid, tannin, and saponin [85]. Bioavailability  
Food as well as host-related factors contribute to the bioavailability and bioaccessibility of carotenoids. Previous studies have demonstrated that the bioavailability of carotenoids (i.e., \(\beta\)-cryptoxanthin) under in vitro conditions ranged from 0.1% to almost 100% [86, 87, 88]. In spite of much attention on lutein, owing to its essential effects such as its antioxidant properties, little information is available regarding its pharmacokinetic properties. [PERSON] et al., calculated the bioavailability of lutein to be 5.20% and showed that a large amount of lutein accumulated in the intestinal mucosa [89]. In addition, the absorption of lutein is improved significantly by food intake. The ability to respond to lutein and blood lutein status are related in humans [90]. Lutein can either exist in the free form or be esterified to fatty acids, and the bioavailability of lutein diester formulation is higher than the free lutein formulation [82]. It is necessary that dietary lutein and zeaxanthin esters be hydrolyzed by enzymes in the gastrointestinal tract before their uptake, since only free forms of xanthophylls can be absorbed into the circulation [91]. Potential Health Benefits  
Dietary cryptoxanthin has several bioactive anti-oxidant, anti-atherosclerosis, and anti-aging properties and can be converted into vitamin A. It can reduce oxidative damage, and protein loss and improve acute nephritis and immunity [81]. In general, there is evidence to suggest that \(\beta\)-cryptoxanthin has beneficial effects in animal models of both non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease [92]. In addition, previous studies have documented the use of \(\beta\)-cryptoxanthin as a nutritional regulators of adipose tissue to be a feasible strategy for preventing obesity and obesity-related metabolic diseases of humans [93]. Specific carotenoids and carotenoid derivatives restrain adipogenesis and adipocyte hypertrophy, while they enhance the fat oxidation and energy dissipation in brown and white adipocytes, and counteract obesity in animal models, indicating a beneficial effect of \(\beta\)-cryptoxanthin supplementation. Moreover, \(\beta\)-cryptoxanthin alleviated myocardial ischemia/reperfusion injury by inhibiting nuclear factor-kappa B (NF-kB)-mediated inflammatory signaling in rats [94].