Stabilizing Vitamin C: L-Ascorbic Acid vs Lipophilic & Ethyl Esters (Engineering Review 2008)
Formulating unoxidized, bioavailable L-Ascorbic Acid requires strict pH regulation and stabilization co-antioxidants.
Engineering Mechanism & Kinetic Flowchart
The Duke Formulation Parameters
Unmodified L-Ascorbic Acid (pKa 4.2) requires an aqueous formulation pH < 3.5 to keep the molecule unionized for passive stratum corneum absorption. Adding 0.5% Ferulic Acid and 1.0% Alpha-Tocopherol increases photoprotective efficacy eight-fold via synergistic free-radical scavenging.
Lipophilic Tetrahexyldecyl Ascorbate (THD)
THD is a tetra-esterified, oil-soluble precursor that seamlessly crosses lipid membranes, undergoing intracellular enzymatic cleavage into ascorbic acid without the erythema associated with low-pH water serums.
Tyrosinase Inhibition & Melanogenesis Regulation
Ascorbate inhibits cutaneous hyperpigmentation by chelating copper ions at the catalytic site of tyrosinase, while simultaneously reducing dopaquinone back into L-DOPA.
Pharmacist-Biochemist · Specialist in Cosmetic Engineering & Dermato-Pharmacology · Published on January 17, 2008 at 18:24
