Antioxidant activity of curcuminoids

Area of Science:

• Natural product chemistry
• Computational chemistry
• Biochemistry

Background:

• Curcuminoids, including curcumin, demethoxycurcumin, and bisdemethoxycurcumin, are natural antioxidants derived from Curcuma longa.
• Understanding their antioxidant mechanisms is crucial for potential therapeutic applications.
• Previous studies suggest significant antioxidant potential, but molecular-level insights are needed.

Purpose of the Study:

• To explore the antioxidant power of curcumin, demethoxycurcumin, and bisdemethoxycurcumin.
• To investigate the role of intramolecular hydrogen bonding and solvent effects on antioxidant activity.
• To elucidate the fundamental molecular factors governing their antioxidant capacity.

Main Methods:

• Computational calculations were performed for 15 isomers of curcuminoids.
• Simulations were conducted in the gas phase and in solvents (water and ethanol).
• Antioxidant activity was evaluated using the hydrogen atom transfer (HAT) and single electron transfer (SET) mechanisms.

Main Results:

• Intramolecular hydrogen bonds significantly influence antioxidant power via both HAT and SET mechanisms.
• Solvent presence consistently enhances the antioxidant activity of all studied curcuminoid structures.
• All evaluated curcuminoid isomers demonstrated superior antioxidant potential compared to phenol and approached or surpassed that of vitamin E.

Conclusions:

• The study provides molecular-level evidence explaining experimental antioxidant observations of curcuminoids.
• Hydrogen bonding and solvent effects are key determinants of antioxidant efficacy.
• Curcuminoids represent promising natural antioxidants with significant potential for health applications.