Enzymatic Metabolism of Flavonoids by Gut Microbiota and Its Impact on Gastrointestinal Cancer

Simple Summary Flavonoid’s consumption is reported to impact GI cancer progression positively. As 90% of flavonoids consumed, undergo metabolism and conversion by the human gut microbiome, understanding their enzymatic bioconversion and metabolism could advance the current knowledge of their anticancer activities. While it is reported that specific flavonoids target cancer-related pathways such as apoptosis, inflammation and cellular proliferation, efforts are required to assess the possibility of combining those specific flavonoids together or with current treatment such as chemotherapy and evaluate their effect on the pathogenesis of GI cancer. Additionally, Studies aimed to standardize flavonoids administered concentration, purification and isolation methods are required. Abstract Gastrointestinal (GI) cancer is a prevalent global health disease with a massive burden on health care providers. Internal and external factors such as obesity, smoking, diet (red meat), low socioeconomic status and infection with Helicobacter pylori are the critical risk factors of GI cancers. Flavonoids are natural phenolic compounds found abundantly in fruits and vegetables. Upon ingestion, 90% of flavonoids consumed require further enzymatic metabolism by the gut microbiome to enhance their bioavailability and absorption. Several epidemiological studies reported that consumption of flavonoids and their enzymatic conversion by gut microbes is strongly associated with the reduced risk of GI cancer development. This review summarizes the current knowledge on the enzymatic conversion of flavonoids by the human gut microbiome. It also addresses the underlying anti-GI cancer effects on metabolic pathways such as apoptosis and cellular proliferation. Overall, metabolites produced from flavonoid’s enzymatic conversion illustrate anti-GI cancer effects, but the mechanisms of action need further clarification.