Comparatively Speaking: Sterol vs. Stearyl

Many terms used in personal care formulating sound and look alike yet have vastly different meanings. This primer for novice chemists examines the terms sterol and stearyl.

Sterols,1 also called steroid alcohols, are natural steroids with a hydroxyl group at the 3-position of the A-ring. Sterols of plants are called phytosterols, and sterols of animals are called zoosterols. Important zoosterols are cholesterol and some steroid hormones; notable phytosterols include campesterol, sitosterol and stigmasterol. Ergosterol is a sterol present in the cell membrane of fungi, where it serves a role similar to cholesterol in animal cells.

Sterols and related compounds play essential roles in the physiology of eukaryotic organisms. For example, cholesterol forms part of the cellular membrane in animals, where it affects the cell membrane's fluidity and serves as a secondary messenger in developmental signaling. In humans and other animals, corticosteroids such as cortisol act as signaling compounds in cellular communication and general metabolism.

Phytosterols may block cholesterol absorption sites in the human intestine thus helping to reduce cholesterol in humans

Stearyl is term used in association with a compound that contains 18 carbon atoms. An example is stearyl alcohol, which has the formula: CH3-(CH2)17OH. Stearyl alcohol is also called octadecyl alcohol or 1-octadecanol.

Stearyl alcohol can also be natural, or synthetic. Additionally, natural stearyl alcohol can be either plant-derived (from coconut oil, for example) or animal-derived (i.e., tallow). Stearyl alcohol is used in hair conditioners and as a raw material to make some cosmetic esters.


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