Source Naturals L-Proline L-Lysine contains L-Lysine, whichis one of the 9 essential amino acids that cannot be made in the body. Source Naturals L-Proline L-Lysine is the basic raw material for carnitine synthesis. Source Naturals L-Proline L-Lysine also contains L-Proline, whichcan be made in the body, but low protein/vegetarian diets may not always promote optimal L-proline production. Source Naturals L-Proline L-Lysine amino acids are the precursors of hydroxylysine (HL), and hydroxyproline (HP), two constituents of collagen. Collagen is an essential component of arterial linings. Vitamin C, a strong antioxidant, is also essential for the production of collagen. Hawthorn berry and grape seed extract are potent antioxidants due to their high levels of proanthocyanidin. These proanthocyanidin-esters are excellent free radical scavengers.