If iron chelators work in Parkinson’s there should be some positive effect with supplemental quercetin. I very much doubt there will be. See the page on Parkinson’s disease. If quercetin does not work in the treatment of Parkinson’s disease then the narrative that treatment of Parkinson’s disease requires iron chelation has to be re-thought. I would avoid supplementing with quercetin until there are definite clinical studies to the effect that quercetin in the real world ameliorates symptoms of Parkinson’s disease which I think will be never.
Quercetin is found in fruits and vegetables. Querectin found in foods could have benefcial effects. Like other antioxidants, when obtained from food, quercetin could have beneficial effects.
Increasing levels of free antioxidants via supplmentation could be much worse than useless. Before iron can be absorbed iron must be reduced from Fe3+ to Fe2+. Antioxidants like vitamin C, vitamin E , beta-carotene and quercetin could one way or other promote the reduction of Fe3+ to Fe2+ in the gastrointestinal tract which would increase absorption. The goal, however, is to delay iron absorption as long as feasible.
There is oxidant stress in lots of illnesses but this could be due to dysregulation of selenoproteins and dysregulation of iron metabolism which would not be fixed by increasing levels of free antioxidants with supplemental vitamin C, vitamin E , beta-carotene, quercetin etc.
Supplementing with free antioxidants could be associated with very subtle but serious mineral dysregulations which would basically be undiagnosable.