MicroActive® L-Citrulline


Nitric oxide (NO) is a very important molecule in human physiology that is vital to the maintenance of proper vascular function.

While NO is synthesized by the enzyme nitric oxide synthase (NOS) from the amino acid L-arginine, oral supplementation of L-arginine is largely ineffective in producing NO — this is due to elimination by another enzyme, arginase, in the gastrointestinal tract and liver before L-arginine can reach the bloodstream.

L-citrulline, on the other hand, is an amino acid that is not affected by the arginase enzymes that break down arginine, and is instead rapidly converted to L-arginine in a two-step conversion.

L-citrulline is one of the three dietary amino acids in the urea cycle, along with L-arginine and L-ornithine.

Upon entering the cell, L-arginine is acted on by NOS to produce the signal molecule nitric oxide, but also L-citrulline, hence establishing a L-citrulline/L-arginine cycle. In fact, intracellular L-citrulline provides an additional source of L-arginine and NO production.

MicroActive® L-Citrulline is a free-flowing powder comprised of 60% active ingredient. As noted, L-citrulline is an amino acid that is converted by the body to arginine. Since it is better absorbed than arginine it is a more bioavailable source.*

Water-soluble L-citrulline passes through the digestive system quickly, with some portion absorbed and the remainder eliminated. Prior research studies on other water-soluble active ingredients indicate that a sustained-release form is more bioavailable; this would enhance the naturally occurring improved bioavailability in the conversion to arginine.*

MicroActive L-citrulline supplementation results in reduced fatigue and improved endurance for both aerobic and anerobic prolonged exercise.*

As mentioned, supplementing with MicroActive L-citrulline also increases ornithine and arginine plasma content — this means L-citrulline supplementation improves the ammonia recycling process and nitric oxide metabolism.*


L-citrulline has also been used clinically to alleviate erectile dysfunction caused by circulatory issues.*

Research shows that MicroActive® L-Citrulline supplementation can:*

  • Improve peripheral vascular endothelial function

  • Boost exercise performance

  • Act as an antioxidant

  • Enhance glucose clearance

  • Improve skeletal muscle synthesis

  • Assist sexual function in males




Healthy Aging


    MicroActive® (MA) L-Citrulline increases absorption by reducing particle size to less than 10 microns, thereby promoting more efficient transport through the digestive tract and cell walls.

    In addition, the proprietary mix of polymers in MA L-Citrulline slows the release rate
    allowing for absorption over a longer time period.* Evidence supports the claim that this combination of greater absorption and sustained release creates a more uniform absorption from subject-to-subject,*

    In fact, in a GI simulation study it was shown that MA L-Citrulline, at a 60% concentration,
    exhibited 80% of elemental release (i.e., release of the pure L-citrulline from the formulation) and continued to release for up to 10 hours.


    L-Citrulline is a safe, naturally occurring essential nutrient found in a number of protein food sources, including milk, legumes, meats and fish.

    MicroActive® Citruline is produced using all GRAS-approved ingredients that were subject to numerous safety studies, including acute toxicity in both humans and animals.*