With Transparent Labs Citrulline powder, you get 2,000 mg of fermented L-citrulline in each scoop to amplify blood flow, muscle pumps, and recovery. L-citrulline is an amino acid that was first isolated from the rind of watermelon (Citrullus lanatus), hence the name “citrulline.” This amino acid has gained popularity in recent years as one of the best nitric oxide boosters thanks to its simple absorption and conversion to L-arginine. Since the kidneys can store large amounts of citrulline but not arginine, citrulline is ostensibly the most vital endogenous regulator of nitric oxide production.