# Physiological Effects of Green-Colored Food-Derived Bioactive Compounds on Cancer
## 2 Physiological Effects and Mode of Actions (MoA)
### Isoflavone  
Isoflavone is a group of plant-origin natural flavonoids belonging to the Fabaceae family. For showing structural similarity to 178-estradiol as well as its binding capacity to estrogen receptors and showing weak estrogenic activities, isoflavone is often called phytoestrogens [62]. The estrogen receptor binding properties of isoflavone are attributed to the positions of its hydroxyl groups (7 and 4'), which are identical to those in estradiol [62]. Its benzopyran ring, located in position 3, is what differentiates it from other flavonoids [62]. The positions of the hydroxyl groups on benzene rings are responsible for the biological activities of isoflavone [62]. Soybean and soy products are the predominant source of isoflavone, containing approximately 1-3 mg isoflavone per 1 g of fresh weight [63]. The major isoflavones found in soybean are genistein (50%), daidzein (40%), and glyceitein (10%) [64]. Among the major isoflavones in soybean, genistein has been studied the most against cancer and other illnesses through in vivo and preclinical studies [65]. Isoflavone is present in the intestine as glycosides, which are broken down by 8-glucosidase and the gut microbiota. In general, Isoflavone is readily absorbed in the intestine, however, their bioavailability may vary in different circumstances [66] A recent study demonstrated that the bioavailability of daidzein and genistein in Japanese women after ingestion were 66.9% and 33.7%, respectively [64]. Based on the preclinical and clinical data, it has been suggested that the bioavailability of isoflavone in the human intestine can rely on the type and origin of the isoflavone, population group, dose, and the concurrent meal taken [65, 66].  
Dietary intake of soy isoflavone has shown remarkable anti-carcinogenic activities against breast and prostate cancers in epidemiological studies [67]. It has been reported that the lower incidence of breast and prostate cancers in Asian countries is associated with the high consumption of soy products [68]. In Canada, an ethnically diverse cohort study involving 6235 women with breast cancer revealed that the consumption of dietary isoflavone was associated with decreased mortality [69]. A population-based cohort study in Japan showed that the isoflavone consumption from soy products resulted in a lower incidence of postmenopausal breast cancers [70]. The positive effects of soy isoflavone have also been documented by a case-control study from a large group of Chinese breast cancer patients [71]. Multiple clinical trials reviewed by [PERSON] et al. showed that soy isoflavone consumption was associated with lower incidence and recurrence of prostate cancer among the patients of different ethnic groups [35]. Remarkably, a significant correlation was found between the dietary soy isoflavone intake and the suppression of the prostaglandin pathway among prostate cancer patients [72]. In addition, the potent efficacy of isoflavone and soy products on colorectal cancer has been reported by a case-control study [73].  
Following the epidemiological evidence, potent anti-cancer effects of isoflavone have been reported by preclinical, in vivo, and in vitro studies (Tuli, 2019). Based on those studies, it has been suggested that the anti-cancer effects of isoflavone could be linked with its modulation of estrogen and androgen-mediated signaling pathways, MAPK, NF&B, PI3K/AKT signaling pathways, as well as Bcl-2 and ERK protein levels (Table 1) [74, 75].  
While the evidence on the chemopreventure functions of isoflavones is plentiful, there were also a few instances claiming some adverse health consequences of isoflavone consumption, such as reproductive toxicity, impairing children's growth, and deteriorating natural immunity, which need to be addressed [76]. Currently, soy milk and tofu yogurt enriched with isoflavone are available, further studies are needed in order to expand the use of isoflavones in functional foods.