These oval berries enveloped in a smooth skin are loaded with antioxidant and scores of other nutrients that are highly beneficial to the human body. The gorgeous, luscious beads of grapes that we consume comprise 70-80% water and 15-30% sugar in the form of glucose or fructose. Besides these two main constituents, grapes and grape juice also contain various essential nutrients like magnesium, calcium, manganese, gallic acid, phosphoric acid, salicylic acid, oxalic acid and loads of vitamins and antioxidants: A, B complex, C and K.