I dont see why not, though perhaps not something you'd want to use regularily for gutload, it should be fine for now and then. The flesh and skin part that people typically eat provides Vitamin C, Vitamin K, Thiamin, Niacin, Vitamin B6, Pantothenic Acid, Magnesium, Copper, Folate, Potassium and Manganese.
~calcium to phosphorous ratio:
7:20
EDIT: Wait - is eggplant part of the nightshade family? I think it might be. that means you shouldnt eat too much of it raw, like potatoes, and you shouldnt eat the leaves/stems either.