Recently advocated as a cosmetic ingredient, shea butter continues to pique the interest of cosmetic chemists, perhaps because it has been known for so long in Europe as a useful product from the colonies. But quite apart form its organoleptic and benefits derive from its use formulas, shea butter gives evidence of biological activity in both animals and in humans. First studies of the material were done in the 1930s, with additional studies conducted between 1946 and 1952. But until 1975 very little more was done, so that a whole generation of cosmetic chemists largely forgot about his interesting vegetal constituent.
Shea butter is comprised mostly of fatty acids in which stearic and oleic acids predominate and this is reflected in its high melting point, 38[deg.]C. Its main value may lie in its very large unsaponifiable fraction (5-7) percent as compared to other vegetable oils, particularly those traditionally used in cosmetics (all less than 1 percent). This unsaponifiable fraction is shown in Table 1. One can perceive the presence of isoprenic hydrocarbons (Karitene), which is dependent upon the extraction process used on the shea butter. Complete or nearly complete absence of Karitene indiicates demucilagination during refining, which can produce loss of useful unsaponifiable constituents. In the latter category, most interesting is a high content (up to 75 percent of the unsaponifiable fraction) of triterpenic alcohols, resulting in a lower content of phytosterols (about 5 percent). These proportions are the reverse of those found in other common vegetable oils, such as cocoa butter, which often is compared to shea butter (Figure 2). These triterpenes and sterols are characteristic to the original oils.
The terpenes and sterols in shea butter are found almost entirely as cinnamic esters, making shea butter unique among common oils, whose unsaponifiable constitutents are found as free alcohols. Saponification of course destroys the ester bonds, so that direct fractionation of shea butter indicates only the cinnamates.
Following classical pharmacological technique, shea butter was...