Sterols (ST)

The term sterol embraces all molecules based on the cyclopentanoperhydrophenanthrene skeleton. Here the ring system does not add to the number of DBE. The stereochemistry of the cholesterol molecule is maintained to a large extent by mammalian sterols, which all contain at least one hydroxyl or oxo group attached to carbon 3. Within this category bile acids are prominent classes as well.

Carbon numbers of the cyclopentanoperhydrophenanthrene skeleton (example of cholesterol)

 Sterol numbering diagram

Class abbreviations

Common Name Lipid Class [LIPID MAPS] Abbreviation
Free cholesterol = cholesterol FC
Sterols Sterols [ST01] ST
Cholesteryl ester Cholesteryl esters [ST0102] CE
Steryl esters Steryl esters [ST0102] SE
Bile acids Bile acids and derivatives [ST04] BA
Sterylglycosides Sterylglycosides SG
Acylsterylglycosides Monoradylglycosterols ASG

Specific rules for sterol lipids

  • In shorthand notation ST is also used as class abbreviation. In all cases, class abbreviation is followed by number of C-atoms:number of DB, and separated by semicolon is the number of oxygens, e.g. ST 27:1;O for cholesterol and lathosterol (also zymostenol), or ST 24:1;O5 for an oxidized sterol and for cholic acid and ursocholic acid. The latter is an important point: Some bile acids have an identical mass and molecular formula to oxidized sterols lacking a carboxylic acid group. This must be considered, when class abbreviation “BA” is used.
  • Shorthand notation of further functional groups are written, separated by a semicolon, after the number of oxygens, e.g. BA 24:1;O4;Tau for taurocholic acid (= common name, abbreviation TCA).
  • Following the number of double bonds, proven position and stereochemistry is shown in parentheses. R and S configurations are preferred for side-chain stereochemistry and are shown in square brackets. Alpha, written as a, and beta, written as b, are preferred for ring stereochemistry. Stereochemistry at C-5 introduced by reduction of the Δ5 bond is indicated by 5aH or 5bH. Replacing the number of oxygens, proven positions and stereochemistry of oxygen containing functional groups are shown. If such stereochemistry is known the common name of the compound can be used.
  • For structures fully proven or based on assumption by biological intelligence, such as e.g. cholesterol, cholesteryl esters, steryl esters, bile acids, sterolglycosides, and acylsterolglycosides abbreviations FC, CE, SE, BA, SG and ASG. CE is followed by number of C-atoms:number of DBE of the fatty acid esterified to the hydroxyl group at position 3, e.g. CE 18:2. SE is used as above followed by slash (for monohydroxysterols) or undersore (for polyhydroxysterols) number of C-atoms:number DBE of the fatty acid esterified to the hydroxyl group .
  • MS/MS scans reveal the presence of conjugates,e.g. taurine (Tau) or glycine (Gly), conjugated through an amide bond to the carboxylic acid group of bile acids; sulfuric acid (S) is conjugated to a hydroxyl group through an ester bond; glucuronic acid (GlcA), N-acetylglucosamine (GlcNAc), and hexose (Hex) sugars are assumed to be linked to a hydroxyl group through an acetal linkage.
  • In the case full stereochemistry is known the common names can be used.

Hierarchical shorthand notation for examples of sterols

Species level: Sum composition, Molecular species level: Lipid species with identified acyl/alkyl-residues, Full structure level: Molecular species with functional groups including positions, Complete structure level: Molecular species with functional groups including positions and stereochemistry (acc. to LMSD)
Lipid class Species level Molecular species level Full structure level Complete structure level (= Common Name)
ST (FC) ST 27:1;O ST 27:1;O ST 27:1(5Z);3bOH = FC Cholesterol
ST ST 27:1;O ST 27:1;O ST 27:1(7);5aH;3bOH Lathosterol
ST ST 28:3;O ST 28:3;O ST 28:3(5Z,7Z,22E);24Me[R];3bOH Ergosterol
ST ST 27:2;O3 ST 27:2;O3 ST 27:1(5Z);3bOH;26COOH[25R] 3β-Hydroxycholest-5-en-(25R)26-oic acid
SE SE 43:1* SE 27:1/16:0* CE 16:0 Cholesteryl palmitate
SE SE 45:3* SE 27:1/18:2* CE 18:2(9Z,12Z) Cholesteryl linoleate
SE SE 45:3* SE 27:2/18:1* SE 27:2(8E,24);5aH;3bO(FA 18:1(9Z)) Zymosteryl oleate
ST ST 21:3;O2 ST 21:3;O2 ST 21:1(4Z);3oxo,20oxo Progesterone
ST ST 19:2;O2 ST 19:2;O2 ST 19:1(4Z);17bOH;3oxo Testosterone
SE SE 22:2;O* SE 19:2;O/3:0* SE 19:1(4Z);17bO(FA 3:0);3oxo Testosterone propionate
ST ST 19:2;O2 ST 19:2;O2 ST 19:1(5Z);3bOH;17oxo Dehydroepiandrosterone
ST ST 18:3;O2 ST 18:3;O2 ST 18:3(1,3,5);3OH,17bOH 17β-Estradiol
ST ST 19:2;O2;S ST 19:2;O2;S ST 19:1(5Z);3bS;17oxo Dehydroepiandrosterone sulfate
Dehydroepiandrosterone sulfate structure
BA ST 24:1;O5 ST 24:1;O5 BA 24:0;5bH;3aOH,7aOH,12aOH;24COOH Cholic acid (CA)
BA ST 24:1;O3 ST 24:1;O3 BA 24:0;5bH;3aOH;24COOH Lithocholic acid (LCA)
BA BA 24:1;O4;Tau BA 24:1;O4;Tau BA 24:0;5bH;3aOH,7aOH,12aOH;24COT Taurocholic acid (TCA)
BA BA 24:1;O3;Gly BA 24:1;O3;Gly BA 24:0;5bH;3aOH,7aOH;24COG Glycochenodeoxycholic acid (GCDCA)
BA ST 24:1;O4;HexNAc ST 24:1;O4;HexNAc BA 24:0;5bH;3aOH,7bOGlcNAc;24COOH Ursodeoxycholic acid 7β-N-acetylglucosaminide (UDCA-GlcNac)
BA SE 40:0;O3* SE 24:0;O3/16:0* BA 24:0;5bH;3bO(FA 16:0),12aOH;24COOH 3β-Palmitoyl isodeoxycholic acid
SG SG 27:1;O;Hex SG 27:1;O;Hex SG 27:1(5Z);3bOGlc Cholesterol glucoside
ASG ASG 29:2;O;Glc;FA20:3 ASG 29:2;O;Glc;FA20:3 ASG 29:2(5Z,22E);24Et[S];3bOGlc;6O(FA 20:3) 20:3(11Z,14Z,17Z)-Glc-Stigmasterol
20:3-Glc-Stigmasterol structure

* At the species level and molecular species level the assumption is made for sterol esters that the ester group contains two oxygen atoms and one double bond equivalent, which are not then included in the notation at these levels.