Important Joint Lubricant With L-Proline, Alpha Lipoic Acid and Grape Seed Extract Hyaluronic Acid is a compound present in every tissue of the body, with the highest concentrations occurring in connective tissues such as skin and cartilage. Hyaluronic Acid is an important constituent of joint fluid, where it serves as a lubricant and plays a role in resisting compressive forces. L-Proline, Alpha Lipoic Acid and Grape Seed Extract have been included to create a more complete formula.