L-Arginine Synonyms: ARG;L-ARG;H-ARG-OH CAS: 74-79-3 MF: C6H14N4O2 MW: 174.2 Appearance: white crystal or white powder, bitter, melt in water Functions: Arginine is a part of ornithine, which has tremendous effect of physiometry. L-arginine has been used for erectile dysfunction. Like the drug Weilinafil citrate (Viagra), L-arginine is thought to enhance the action of nitric oxide, which relaxes muscles surrounding blood vessels supplying the penis. As a result, blood vessels in the penis dilate, increasing blood flow, which helps maintain an erection. The difference in how they work is that Viagra blocks an enzyme called PDE5 which destroys nitric oxide and L-argentine is used to make nitric oxide.