Flavones

Flavones (flavus = yellow), are a class of flavonoids based on the backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran-4-one) (right image). Flavones (flavus = yellow), are a class of flavonoids based on the backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran-4-one) (right image). Flavones are common in the food supply, mainly from spices, and red–purple fruits and vegetables. Common flavones include apigenin (4',5,7-trihydroxyflavone), luteolin (3',4',5,7-tetrahydroxyflavone), tangeritin (4',5,6,7,8-pentamethoxyflavone), chrysin (5,7-dihydroxyflavone), and 6-hydroxyflavone. Flavones are mainly found in spices and red or purple plant foods. The estimated daily intake of flavones is about 2 mg per day. Flavones have no proven physiological effects in the human body and no antioxidant food value. Following ingestion and metabolism, flavones, other polyphenols, and their metabolites are absorbed poorly in body organs and are rapidly excreted in the urine, indicating mechanisms influencing their presumed absence of metabolic roles in the body. Flavones have effects on CYP (P450) activity which are enzymes that metabolize most drugs in the body. In organic chemistry several methods exist for the synthesis of flavones: Another method is the dehydrative cyclization of certain 1,3-diaryl diketones. The Wessely–Moser rearrangement (1930) has been an important tool in structure elucidation of flavonoids. It involves the conversion of 5,7,8-trimethoxyflavone into 5,6,7-trihydroxyflavone on hydrolysis of the methoxy groups to phenol groups. It also has synthetic potential for example: This rearrangement reaction takes place in several steps: A ring opening to the diketone, B bond rotation with formation of a favorable acetylacetone-like phenyl-ketone interaction and C hydrolysis of two methoxy groups and ring closure.