L-pyroglutamic acid is also known as oxidized proline. Relative molecular mass: 129.12. Melting point: 162-163℃. Insoluble in ether, slightly soluble in ethyl acetate, soluble in water (40 at 25℃), ethanol, acetone and glacial acetic acid. Specific rotation -11.9°(c=2,H2O). Its sodium salt can be used as a moisturizer in cosmetics. Its moisturizing effect is superior to that of glycerin and sorbitol. It is non-toxic and has no irritating effect.