I've ordered the following extracts from China, generally $100 to $200 per kg. The doses I want to simulate from the research in mice and rats pretty much requires extracts instead of whole foods. 20 tangerines and 5 apples a day is not reasonable.
The epidemiological evidence is strongest for >1 apple per day, >5 cups of coffee, and >1 pack of cigarettes, with even stronger effects if the last 2 are doubled.
The compounds in parenthesis below have been tested with good results in PD animal models and the last two were good in epidemiological studies for everyone. For some reason, women did not seem to be protected from PD as a result of citrus intake.
tangerine peel extract (10:1 concentration, estimated 20% nobiletin, 7% tangeretin, 50% hesperidin)
bitter orange peel extract (10% naringin, 30% hesperidin)
apple extract (80% polyphenols, ursolic acid)
Men and women:
blueberry or bilberry extract (25% anthocyanodins)
Grape seed, green tea, and black tea extracts can be added to this list with equal or greater effects in prevention of PD and protection in PD animal models, and they are also known to be absorbed and cross the human blood brain barrier.
This is not a complete list. There is also ginseng, ginkgo, broccoli, and pomegranate with research into PD. Ginkgo seems to have the weakest evidence.