# Physiological Effects of Green-Colored Food-Derived Bioactive Compounds on Cancer
## 2 Physiological Effects and Mode of Actions (MoA)
### Lutein  
Lutein, belonging to the family of xanthophyll, is one of the 600 carotenoids found in nature. This oxycarotenoid is generally found in green leafy vegetables, fruits, egg yolk, marigold flowers, and brown algae [88; 89]. The most abundant natural lutein sources are dark green vegetables, marigold flowers, and microalgae [90]. Currently, lutein comprises 23% of the carotenoid market worldwide [90]. Lutein is a lipophilic compound composed of a 40 carbon backbone with a methyl group attached to it [89]. The carbon-carbon double bonds present in the molecule give it a yellow-orange color by allowing it to absorb light. Unlike most other carotenoids, lutein has two hydroxyl groups at both ends of the carbon chain. In the plant system, lutein is synthesized by the melvonate pathway through an enzymatic breakdown of mevalonate [91]. As a lipophilic compound, the bioavailability of lutein is mainly dependent on the food matrix. After entering the intestine, lutein is transformed as a lipid droplet and eventually as a micelle complex absorbed through the enterocyte [92]. The presence of fat in the carrier food is therefore essential for lutein absorption in the gut. Reportedly, the bioavailability of lutein highly increases when it is fortified in milk and other high-fat foods [93]. Lutein has been widely discussed in the scientific literature for exhibiting numerous health benefits, including eye disease, neurological dysfunctions, cardiac problems, skin irritation, and so on [91]. Recent studies suggest that lutein also shows potential anticancer properties in vivo and in vitro studies [94]. [PERSON] et al. reported that lutein obtained from marigold flowers triggered caspase-3-mediated apoptosis in cervical cancer cells [95]. The effects of lutein against prostate, breast, and cancer cells have been reported elsewhere [96; 97]. It has been shown that lutein could suppress the phosphorylation of protein kinase B, ERK 1/2, and NFkB in breast cancer cells [98]. Lutein has been shown to inhibit breast cancer cells and increase the efficacy of a chemotherapeutic [99]. The results from several epidemiological studies also suggest that the daily intake of lutein could positively affect various types of cancer, including esophageal, breast, lung, colorectal, and pancreatic cancers [100]. These data indicate that lutein has a great potential to be included in the list of natural anti-cancer agents for which more data and extensive evidence from preclinical and human trials are required. Lutein already has a wide application as functional food and medicinal ingredient. Since lutein is easily degradable, the companies are using sophisticated production technologies to preserve the integrity and functions of lutein [90]. Green chemopretion is a relatively new phenomenon, and it has received a breakthrough at the onset of the twenty-first century with a great deal of research, identifying green foods as a source of potential anti-cancer compounds. Numerous studies point out that the chemotherapeutics agents from green foods are effective, safe, and cost-efficient. Green food compounds, including chlorophyll, sulforaphane, isoflavone, and catechins, have shown promising results against different forms of cancer in human trials and in in vivo models. In addition, these compounds have been shown to reverse cancer progression by modulating important biomarkers, such as phase I and phase II enzymes, p53, HDAC inhibitors, and multiple signaling pathways, including PI3K/Akt ERK, BCI-2, and wint signaling. Green foods also contain a number of anti-carcinogenic trace elements, such as folate, riboflavin, retinoic acid, and vitamin D3 (Table 2). The wide application of lutein as pharmaceutical and functional food ingredient makes us believe that other compounds in green-colored foods will follow suit and will be available as chemotherapeutics. However, for their successful application as green chemotherapeutic agents, determining the appropriate and safe doses of these compounds through preclinical and clinical studies is necessary.