Retinyl Ascorbate

What is retinyl ascorbate?

Retinyl ascorbate is an ester created from retinyl chloride and ascorbic acid (R).

Is retinyl ascorbate stable?

Retinyl ascorbate has limited stability in aqueous methanol and aqueous ethanol, and is highly unstable when exposed to light, temperature and atmospheric oxygen. A co-solvent system comprising equal amounts of methanol and phosphate-buffered saline (PBS) at a pH of 4.8 has been found to be more suitable for retinyl ascorbate in terms of both solubility and stability (R).

Does retinyl ascorbate get absorbed?

Retinyl ascorbate dissolved in a mix of methanol + PBS is able to penetrate human skin, but it does so less well than retinyl palmitate and ascorbyl palmitate, perhaps due to its lower stability and lipophilicity (R). Retinyl ascorbate also appears to interact with the skin in a concentration-dependent manner. When it was applied at a concentration of 2.5 mM, it permeated the skin 5x more effectively than at half the concentration (R).

In a tape stripping experiment, 13% of the applied dose of retinyl ascorbate was found in the different layers of the skin. Specifically, 6% was detected in the stratum corneum, 2% in the viable epidermis and 0.2% in the dermis. Another 2% and 0.2% was detected as retinoic acid in the epidermis and dermis, as well as 1.4% and 0.15% as ascorbic acid in the epidermis and dermis (R). Retinyl ascorbate's affinity for the stratum corneum in particular may be explained by its binding to keratin, the major protein in the stratum corneum (R).

Compared to retinyl palmitate and ascorbyl palmitate, more of retinyl ascorbate is retained in the skin, which may be beneficial for the formation of a reservoir and in limiting systemic absorption (R).

Interestingly, a separate study using pig ear skin showed that not much retinyl ascorbate is delivered to the skin through the hair follicles, but that delivery through this follicular route rose by 20% to 40% when the skin was stretched (R).

What happens after retinyl ascorbate is absorbed?

Retinyl ascorbate is hydrolysed in the skin after its uptake. It is first converted chemically to an intermediate, and then hydrolysed by enzymes to form retinoic acid (R). Retinyl ascorbate is more susceptible to hydrolysis than ascorbyl palmitate and retinyl palmitate, indicating that it may be able to more effectively deliver both parent compounds to the viable epidermis (R).