Nutrients are present in all the fruits but in different quantities. Hence, it is essential to be aware of the nutritional value of fruits before we add them to our health routine. Purple Mangosteen vs Watermelon Nutrition will help you choose the best fruit among the two. Carbs in Purple Mangosteen and Watermelon are 15.60 g and 7.55 g respectively. The protein content of Purple Mangosteen and Watermelon is 0.50 g and 0.61 g. Protein to carb ratio of any fruit must be approximately 1.34. Protein to carb ratio of Purple Mangosteen is 0.03 and in Watermelon, it is 0.08. Nutritional value of fruits is incomparable to other food items. They provide all the vital nutrients required for proper functioning of our body.