Retinyl esters are not alike: an in vitro study

Retinol is well-established in cosmetics as an anti-ageing ingredient. It is known to increase cell proliferation and production of extracellular matrix elements such as hyaluronic acid. Anti-ageing products containing retinol may therefore decrease the appearance of wrinkles and improve skin texture. Unfortunately, retinol also suffers from chemical instability and the potential to irritate skin. To circumvent these issues, several derivatives of retinol have been developed with improved stability while still retaining the anti-ageing effects. The derivatives contain unsaturated fatty acids, either purified linoleic acid or a blend derived from sunflower seed oil. A comparative in vitro study was conducted to compare the effect of different test materials on human dermal fibroblast proliferation and production of hyaluronic acid. The test materials included retinol and three different esters of retinol (Retinyl sunflowerseedate, Retinyl linoleate, and Retinyl palmitate). 

The processes underlying changes in the appearance of skin over time, such as the fine lines and wrinkles, are fairly well understood. Natural or intrinsic skin ageing is accompanied by thinning of the epidermis, slower cell turnover and a reduction in the number and thickness of collagen fibres. Aged skin can appear thin, fragile, saggy or wrinkled.1 Extrinsic skin ageing, or photoageing, results from sun exposure and damage can also appear as fine lines and wrinkles along with hyperpigmentation.2

The skin’s extracellular matrix is the primary location for structural proteins such as collagen and elastin responsible for maintaining skin firmness and elasticity. During both extrinsic and intrinsic skin ageing, reactive intermediates induce the expression of matrix metalloproteinases (MMP). These proteases break down collagen in the skin, and degraded collagen and reduced collagen synthesis are both diagnostic of naturally aged and photoaged skin.3 Skin ageing is also associated with loss of skin moisture which can contribute to loss of firmness. The key molecule involved in skin moisture is hyaluronic acid (HA), an extracellular matrix component with a very high water-binding capacity.4