Some Wikipedia background readings on
a) the function of quercetin, (inhibition of directional and localised growth in specific parts/areas of of plants in response to gravi-/photo-tropism, among other things),
b) the effect of the pH environment on the integrity of such molecules and their corresponding level of activity (strong in acidic env., weak in alkaline env., )
would be inclined to make sense of 脱 as a contextual short for 脱水 (for ‘hydrogen-stripped’), which amounts to qualify that quercetin molecule as ‘dissociated’, ‘broke up’, ionised’. and account for the resulting inactivity/negligible capacity of its naked radical to transfer to a neighboring cell.

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Note added at 4 days (2015-10-12 11:13:56 GMT)
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Nope! Revisiting this late offering, I conclude:
- the facts summarised from the links accessed may be correct but are not the main reason for the interest of the pharma industry for it . Its anti-inflammatory function is far more important.
- but more importantly, the expression suggested for 脱　(Hydrogen-stripped) is far too strong for the case referred to. Dissociation / ionisation does not require all 10 H electrons to be captured and bonded to the new medium the Quercetin finds itself in. If it did, its 5 component hydroxyls would become something else, which I think is unlikely.
so what might a better phrase? ‘dissociated quercetin’ might be safer, upon reflection…