Triplet-Energy Quenching Functions of Antioxidant Molecules

Area of Science:

• Biochemistry
• Photochemistry
• Molecular Biology

Background:

• UV-like DNA damage can occur endogenously via chemiexcitation.
• This process involves enzymes generating reactive species that form dioxetanes on melanin, leading to excited carbonyls that transfer energy to DNA.

Purpose of the Study:

• To screen natural compounds for their ability to quench triplet-state energy transfer to DNA.
• To differentiate true quenchers from reactive oxygen and nitrogen species scavengers.

Main Methods:

• Chemiexcitation was used to generate excited carbonyls.
• Tetramethyl-1,2-dioxetane (TMD) was used to generate triplet-state acetone.
• 9,10-dibromoanthracene-2-sulfonate (DBAS) served as a triplet-energy reporter, with quenching measured by luminescence reduction.
• Inhibition concentrations for quenchers were determined.

Main Results:

• Natural compounds including polyenes, polyphenols, and mycosporine-like amino acids were identified as potential quenchers.
• Three clusters of inhibitory concentrations were observed: ~50 μM, 200-500 μM, and >600 μM.
• Sorbate, ferulic acid, and resveratrol were among the most effective quenchers (~50 μM).
• Effective quenchers prevented the formation of dark cyclobutane pyrimidine dimers (dCPDs) in DNA and melanocytes.

Conclusions:

• The delocalized pi electron cloud in antioxidants enables them to prevent energy transfer from excited species to DNA.
• The most effective triplet-state quenchers function via energy diversion and dissipate energy through isomerization, rather than electron donation.