Chemical equation to represent the hydrogen peroxide scavenging experiment, used to determine antioxidant ability of tea
I start by quoting a source (which also goes into great detail on explaining the underlying mechanism of chromophores excitation):


  Photosynthesis is initiated by the absorption of light by the chromophores, which excites the molecules from the ground state to an electronic excited state.


So, simply:

$\ce{Chromophores + hv -&gt; *[Chromophores] -&gt; [Chromophores](e-,h+)}$

with the creation of an electron and an electron hole. Now, absence the H2O2, the action of the electron-hole on OH- on water creates an hydroxyl radical:

$\ce{OH- + h+ -&gt; .OH }$

Also, in the further presence of H2O2, a path to the so-called one-electron reduction of hydrogen peroxide from the action of a formed electron (e-) on H2O2, resulting in an additional hydroxyl radical:

$\ce{H2O2 + e- (aq) -&gt; .OH (aq) + OH- (aq) }$

Now, as the tea acts acts as a radical scavenger, it reacts with the hydroxyl radical usually via an H atom extraction reaction forming water. For example:

$\ce{RH + .OH -&gt; .R + H2O}$

The hydroxyl radical continues to attack the chromophores until there is just simple colorless products like CO2 and H2O. In time, the tea solution becomes colorless.

Now, in the combined chromophores and H2O2 experiment, the UV absorbance by tea solution should measurably display more decline with time due to the increased hydroxyl radical concentration.