L-norvaline is an analog of valine, a branched-chain amino acid. Research suggests that it has a powerful inhibitory effect on the activity of arginase and may significantly increase levels of arginine and thus endogenous production of nitric oxide (NO) of which it is the precursor.

¤ Nitric oxide is an important signalling molecule in the body, acting in various tissues to regulate a range of physiological processes including vasodilation of blood vessels, blood pressure and circulation, function of brain cells, inflammation, apoptosis ( programmed cell death), and immune or sexual function.

¤ Branched-chain amino acids are classic arginase inhibitors - several cell studies suggest that L-norvaline is one of the most powerful. In a trial on macrophages, it indirectly exerted this effect through the inhibition of ornithine transcarbamylase which converts ornithine into citrulline as part of the urea cycle. This induces accumulation of ornithine which in turn inhibits the activity of arginase, thus increasing arginine and nitric oxide production. These mechanisms occur across a variety of tissues and cells, in the vascular endothelium as well as in white cells and platelets.