¡@¡@Flavonoids are phenolic substances isolated from a wide range of vascular plants, with over 8000 individual compounds known. They act in plants as antioxidant, antimicrobials, photoreceptors, visual attractors, feeding repellants, and for light screening. Until now, many studies shows flavonoids have ability to reduce free radials and to scavenge free radials. Although most ingested flavonoids in our gastrointestinal are extensively degraded to various phenolic acids, some of which still scavenge free radials. Both the absorbed flavonoids and their metabolites may display an in vivo antioxidant activity.
Flavonoids are formed from the aromatic amino acids phenylalanine and
tyrosine, and malonate. The varous classes of flavonoids differ in the
level of oxidation and pattern of substitution of the C ring.¡@¡@Flavonoids act as scavengers by two ways.
1. Flavonoids inhibit the enzymes responsible for superoxide anion production.
¡@¡@Flavonoids have been reported to inhibit many enzymes involving in ROS generation. And a number of flavonoids can chelate trace metal ions which play an important role in oxygen metabolism, as Cu+ and Fe2+.Such metal ions are potential enhancers of ROS formation.
2.Flavonoids(Fl-OH) are thermodynamically able to reduce highly oxidizing free fadials with redox potentials in the range 2.13-1.0V.
¡@¡@the figure below shows the
hypothesis pathway of scavenging ROS by flavonoids.
