Effect of blue light irradiation on the stability of phospholipid molecules in the presence of epigallocatechin-3-gallate

In this paper, we report on the effects from epigallocatechin-3-gallate (EGCG), a phytochemical flavonoid present in green tea, on Langmuir monolayers of 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol) (sodium salt) (DPPG), including experiments with blue light irradiation. EGCG was found to interact with both the DPPG headgroups and hydrophobic tails, thus affecting the lipid packing according to surface pressure and surface potential isotherms and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) data. Blue light irradiation caused considerable changes in the surface pressure isotherms and PM-IRRAS spectra of DPPG monolayers, but the effects were considerably less when EGCG was present. For the surface pressure isotherms, for instance, no irradiation effect could be measured for mixed EGCG-DPPG monolayers. It is concluded that EGCG protected the DPPG molecules from degrading upon blue light irradiation, which means that EGCG may be a preventive and therapeutic agent to decrease photosensitivity of phospholipids to blue light oxidative damage, a pathogenic mechanism in skin disorders.