Effect of microencapsulated watermelon ( Citrullus lanatus ) intake on plasma amino acids and glycemic response in healthy adults

Watermelon is an l -citrulline-rich fruit that has been used as a supplement to increase l -arginine in plasma, which in turn plays a critical role in the synthesis of nitric oxide, a molecule that regulates vascular tone. Watermelon rind, similar to its pulp, presents a high l -citrulline content, yet a lower concentration of sugar, which would be more convenient for individuals who need to refrain from excessive sugar ingestion (i.e., diabetics and obese individuals). Further, ingestion of watermelon rind can be a sustainable alternative to increase plasma l -arginine, given that rind of fruits is commonly discarded. Therefore, we evaluated the effect of ingestion of a product derived from watermelon rind and pulp (microencapsulation in spray drier) on plasma amino acids ( l -citrulline, l -arginine and l -ornithine), glucose, and insulin. Eleven participants (28.36 ± 5.70 years) were enrolled in a single blind, cross-over and randomized study. They ingested microencapsulated watermelon rind and pulp (containing 4 g of l -citrulline) plasma amino acids, glucose, and insulin were evaluated before and 30, 60, 90 and 120 min after ingestion. It was observed that both microencapsulated watermelon rind and pulp increased l -citrulline through 120 min and microencapsulated watermelon rind significantly increased l -arginine at 30 min. In addition, microencapsulated watermelon rind and pulp similarly increased plasma glucose and insulin levels. In conclusion, these findings suggest that both microencapsulated watermelon rind and pulp are effective to increase plasma l -citrulline and microencapsulated watermelon rind effectively increases plasma l -arginine. In addition, rind and pulp promote similar changes on plasma glucose and insulin.