The saturated methyl branched fatty acids of adult human skin surface lipid

In adult human skin surface lipid, the saturated branched fatty acids are made up of the same type of compounds present in vernix caseosa lipid but in different amounts. This implies that these compounds are truly endogenous products of the adult human being. The basic carbon skeletons of these compounds are normal even, normal odd, iso even, iso odd and anteiso odd (‘even’ and ‘odd’ referring to the number of C-atoms in the chain). The internal portion of each type of chain can contain additionally mainly one but sometimes two and rarely even three methyl branches all located on the even numbered C-atoms from the carboxyl group. The 4-methyl position is favored. These internal methyl branched acids are most likely biosynthesized by substitution of an occasional methylmalonyl-CoA for malonyl-CoA by the appropriate starter after the chain has been begun to yield the five basic carbon skeletal types of chain listed above. Thus, by varying the starter, the chain length, and the position of the internal methyl branch, numerous acids are formed even though they constitute only about 11% of the total saturated acids of AHSSL. It is postulated that these acids are made in slightly different amounts for each individual and constitute a part of his ‘chemical signature’.