Medium and substitution pattern effects on the action of hydroxyflavones as photoprotectors against singlet molecular oxygen-mediated photooxidation of fats

✍ Scribed by Criado, Susana ;García, Norman A. ;Gutiérrez, Maria I. ;Avila, Vicente ;Bertolotti, Sonia G. ;Cuarto, Rio

• Publisher: John Wiley and Sons
• Year: 1996
• Weight: 402 KB
• Volume: 98
• Category: Article
• ISSN: 0931-5985
• DOI: 10.1002/lipi.19960980504

✦ Synopsis

Abstract

The ability of mono‐, di‐, tri‐and tetra‐hydroxyflavones (7‐and 3‐hy‐droxyflavones, 7, 8‐dihydroxyflavone, baicalein and fisetin) to act as photoprotectors against singlet molecular oxygen [O^2^(Δ~g~)]‐initiated photooxidation of fats has been established by a kinetic study. The overall quenching rate constants for a series of five hydroxyflavones perfectly parallel their respective behaviour as inhibitors of the sensitized photooxidation of linoleic acid. The best antioxidative effect was exerted by 7‐hydroxyflavone which does not chemically react with O^2^(^1^Δ~g~). Nevertheless for the remaining flavonoids of the series, the physical deactivation of O^2^(^1^Δ~g~) largely prevails over the chemical process.

As for the cases of phenols and related hydroxy‐aromatic derivatives, the ionization of the ‐OH group in the flavones, dramatically accelerates the rate of photooxidation. Under these conditions, the 7‐hydroxyflavone also reacts effectively with O^2^(^1^Δ~g~). Given that flavonoids are natural oil components, this medium effect should be taken into account during the oil‐refining process, in order to avoid the flavonoid photodestruction.