Apples are a significant source of vitamin C , a moderate sources of potassium and low in most everything else. The peel does add significant fiber . A pie crust of flour, shortening and salt adds thiamin , riboflavin and niacin if it is made from enriched or whole-wheat flour. When making a crust, you can reduce the salt or leave it out completely to reduce the sodium content. Since the raw apples cook in the pie, some of the vitamin C lost during cooking one hour at 400 degrees would remain in the pie.
Potassium is a mineral, like calcium .
It is not lost in cooking. Your apple pie should have the majority of nutrients of the fresh apples that went into it.