L-ascorbic acid, also known as vitamin C, is a powerful antioxidant involved in several biological processes such as collagen synthesis, intestinal absorption of iron, and the metabolism of selected amino acids.
Magnesium ascorbyl phosphate (MAP; L-ascorbic acid 3-phosphate magnesium salt) is an esterified derivative of Vitamin C. Unlike L-ascorbic acid, which is lipophobic (only water-soluble), has low pH, and is unstable; MAP is a lipophilic and water-soluble form of vitamin C, which is stable at neutral pH and easily absorbed through the skin. In addition, it is durable against hydrolysis in neutral or alkaline solutions. In contrast, it is readily hydrolyzed in the skin to L-ascorbic acid, and inorganic phosphate by acidic phosphatases are present naturally in the human skin. However, ascorbic acid is volatile in front of light and oxygen, so stable Magnesium Ascorbyl Phosphate salt is ideal for delivering vitamin C.
It is one of the most potent antioxidants for the skin, and magnesium ascorbyl phosphate protects against photoaging, UV-induced immunosuppression, or cancer formation. It also increases collagen synthesis, stabilizes those fibers, and decreases destruction.
Like an L-ascorbic acid, it reduces melanin synthesis (by tyrosinase inhibition - a regulating enzyme responsible for melanin production), acting as a very effective lightening and brightening agent on unevenly toned skin or areas of unwanted hyperpigmentation (i.e., age spots). In addition, MAP is the initial defender of tocopherols and acts together with vitamin E to protect against oxidative stress. It is a very safe ingredient without toxicity and irritation. In contrast with other vitamin C derivatives like ascorbyl palmitate or stearate, magnesium ascorbyl phosphate doesn't destabilize formulations and found its practical niche in the industry of high-end skincare products.