Sun dried grapes turn into raisins and this process has been done from ancient times.
Raisins are a rich source of carbohydrates, 94% of which are glucose and fructose - harmless sugars for diabetics. Raisins contain vitamins C, P, PP, B1 and B2, carotene, potassium, calcium, phosphorus, magnesium, manganese, selenium, organic acids.
Raisins are a major source of micromineral boron, which helps to  strengthen  our bones.

They contain antioxidants and especially oleanolova acid. They are rich in iron.