Related Experiment Videos
Structural aspects of antioxidant activity of flavonoids
S A van Acker1, D J van den Berg, M N Tromp
1Department of Pharmacochemistry, Vrije Universiteit, Netherlands.
Abstract:
Flavonoids, a group of naturally occurring antioxidants and iron chelators, might be used as cardioprotective agents in doxorubicin-induced cardiotoxicity, which is believed to be caused by the formation of oxygen free radicals. To investigate the underlying molecular mechanism, we tested a large group of flavonoids from all major structural subclasses on their ability to inhibit doxorubicin (enzymatically)-induced and Fe2+/ascorbate (nonenzymatically)-induced microsomal lipid peroxidation (LPO) and to chelate Fe2+. In addition, we measured half peak oxidation potentials (Ep/2). LPO inhibition data gave a good qualitative correlation with the oxidation potentials. Most flavonoids tested chelated Fe2+, but there were large differences in the chelating capacity. For good scavenging activity, a catechol moiety on ring B is required. The 3-OH moiety can function as a chelation site and can also be oxidized. The 3-OH group in combination with a C2 C3 double bond, increases the scavenging activity. Fe2+ chelation only plays a role in the LPO inhibition by less active scavengers. Chelation can then raise the activity to the level of the most active scavengers, possibly by site-specific scavenging. It can be concluded that Ep/2 values and iron chelating activity can almost completely describe the LPO inhibiting behaviour of the flavonoids.
Insights
Flavonoids can protect against doxorubicin cardiotoxicity by inhibiting lipid peroxidation. Their antioxidant and iron-chelating properties, particularly the B-ring catechol and 3-OH group, are key to this cardioprotective effect.
Area of Science:
- Biochemistry
- Pharmacology
- Cardiovascular Research
Background:
- Doxorubicin cardiotoxicity is a significant clinical challenge, linked to oxidative stress and free radical formation.
- Flavonoids, natural antioxidants and iron chelators, show potential for cardioprotection against drug-induced damage.
Purpose of the Study:
- To investigate the molecular mechanisms by which flavonoids inhibit doxorubicin-induced cardiotoxicity.
- To evaluate the structure-activity relationships of various flavonoids in preventing lipid peroxidation and chelating iron.
Main Methods:
- Tested a diverse range of flavonoids for their ability to inhibit enzymatic and non-enzymatic microsomal lipid peroxidation (LPO).
- Assessed the iron (Fe2+) chelating capacity and measured half peak oxidation potentials (Ep/2) of flavonoids.
- Correlated LPO inhibition with flavonoid structure, oxidation potential, and iron chelation.
Main Results:
- Flavonoid antioxidant activity correlated with their oxidation potentials (Ep/2).
- Most flavonoids chelated Fe2+, with significant variations in capacity; a catechol moiety on ring B is crucial for potent scavenging.
- The 3-OH group, especially with a C2-C3 double bond, enhances scavenging activity. Iron chelation enhances the activity of less potent scavengers, possibly via site-specific mechanisms.
Conclusions:
- Flavonoid's iron-chelating ability and oxidation potential largely determine their efficacy in inhibiting lipid peroxidation.
- Specific structural features, like the B-ring catechol and 3-OH group, are critical for the cardioprotective antioxidant activity of flavonoids against doxorubicin toxicity.