Mechanism of Catechin Chemiluminescence in the Presence of Active Oxygen

The photon emission (chemiluminescence; CL) of catechin in the presence of active oxygen species (hydrogen peroxide, hydroxyl radical tert-butyl hydroperoxide and tert-butyl oxyl radical) and acetaldehyde was confirmed to occur non-enzymatically at room temperature in aqueous neutral conditions. The CL intensity [P] in the presence of active oxygen species (X), catalytic species (Y) and receptors (Z) is predicted by [P] = k [X] [Y] [Z]. The calculated photon constants (k) of 8 catechins and gallic acid were 8.23 x 10(6) M-2 s-1 counts ((-)-epigallocatechin), 2.78 x 10(8) ((-)-epigallocatechin gallate), 4.66 x 10(5) ((-)-gallocatechin gallate), 4.36 x 10(5) ((-)-gallocatechin), 2.70 x 10(5) ((-)-epicatechin), 6.44 x 10(4) ((-)-catechin), 585 x 10(4) ((-)-epicatechin gallate), 4.78 x 10(4) (gallic acid) and 3.54 x 10(4) ((-)-catechin gallate), respectively. The system of active oxygen species, catalytic species and receptors is proposed to be a scavenging mechanism for active oxygen species. In the presence of acetaldehyde, (-)-epigallocatechin (maximum k value among catechins tested) reacted with tert-BuOOH to form tert-BuOH as determined by HPLC analysis.