Gregory Petsko — American Scientist

Gregory A. Petsko is an American biochemist and member of the National Academy of Sciences. He has an endowed professorship at Weill Cornell Medical College, is an adjunct professor at Cornell University, and is a professor emeritus at Brandeis University... (wikipedia)

Alzheimer's disease starts when a protein that should be folded up properly misfolds into a kind of demented origami.
As far as protecting yourself against Alzheimer's disease, well, it turns out that fish oil has the effect of reducing your risk for Alzheimer's disease. You should also keep your blood pressure down, because chronic high blood pressure is the biggest single risk factor for Alzheimer's disease.
For thousands of years, long before there was such a thing as a science of chemistry, people were fascinated by plants, because they knew that plants contained substances that could affect people. Coffee will keep you awake. Tobacco contains something that will calm your nerves. Foxglove contains an extract that'll affect your heart.
If you want to lower your risk of Parkinson's disease, caffeine is protective to some extent; nobody knows why. Head injuries are bad for you. They lead to Parkinson's disease.
Synthesis is the process of making a natural product, or some other substance, artificially, in the lab, one step at a time, from extremely simple building blocks.