Acyl glycerols

Acylglycerines (previously known as glycerides, glycerides or neutral fats) are organic chemical compounds of the trihydric alcohol glycerine and a maximum of three organic or inorganic acids that are linked by an ester bond . Depending on the ester bonds formed, a distinction is made between monoacyl, diacyl and triacylglycerols (mono-, di- and triglycerides).

Structure and division

Depending on their basic structure, the acylglycerols are divided into different classes: class Basic structure X 1 X 2 X 3 Optical activity Glycerin -H -H -H inactive Monoglyceride -C (O) -R -H -H Yes Monoglyceride -H -C (O) -R -H inactive Diglyceride -C (O) -R 1 -C (O) -R 2 -H Yes Diglyceride -C (O) -R 1 -H -C (O) -R 2 only if R 1 ≠ R 2 Triglyceride -C (O) -R 1 -C (O) -R 2 -C (O) -R 3 only if R 1 ≠ R 3 Phosphoglycerides -C (O) -R 1 -C (O) -R 2 -P (O 2 ) -O-Y Yes

Note: –C (O) –R = fatty acids (acyl residues)

All naturally occurring acylglycerols have the sn configuration , which defines the stereospecific spatial arrangement of the glycerol substituents.

Furthermore, the acylglycerols which are solid at room temperature are called fats , the liquid ones as oils .

Occurrence

Mono- and diacylglycerols have amphiphilic properties and can therefore be components of biomembranes or act as emulsifiers (e.g. when lipids pass from the intestine into the blood ). You can also carry a sugar residue on a remaining free hydroxyl group of the glycerine. These molecules are part of the cell envelope of bacteria , the thylakoid membrane of chloroplasts and the myelin sheath of nerve cells .

Example of a triglyceride in fats and oils. The fatty acid residue marked blue is saturated, the green marked is single, the red marked triple unsaturated . The triple acylated glycerine can be seen in black in the center . Oils contain a higher proportion of essential fatty acid residues (= unsaturated fatty acid residues) than fats.

The most diverse group are the triacylglycerols , in which the glycerol is esterified with three fatty acids. Their structure is diverse, as there are different fatty acids and thus a large number of possible combinations. All are non-polar and therefore lipophilic. In the body they belong to storage and construction fat.

use

The mono- and diglycerides of fatty acids are used as additives ( E 471 ) in the food industry (R = long-chain alkyl or alkenyl residues of saturated or unsaturated fatty acids):

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  Structural formula of a 2-monoglyceride - used as an emulsifier in food

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  Structural formula of a 1,2-diglyceride - used as an emulsifier in food

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  Structural formula of a triglyceride - a component of many foods

Individual evidence

1. ↑ Gregory Cevc: Phospholipids Handbook. CRC Press, 1993, ISBN 9780824790509 , p. 2.