l-citrulline

The amino acid L-citrulline found in watermelons, can be useful in lowering blood pressure in those with hypertension...https://www.naturalnews.com/040082_watermelon_functional_foods_hypertension.html

Here's an article about how L-citrulline in watermelons helps to lower blood pressure. Also mentioned are other watermelon benefits. https://www.naturalnews.com/032183_watermelon_blood_pressure.html