Lipid species are stated by class shorthand abbreviation, followed by a space and number of C-atoms:number of double bond equivalents (C-atoms:DBE), e.g. TG 54:5 or PC 38:3.
DBE can be a C=C double bond, ring structure, or hidden functional groups like keto/aldehyde and triple bond.
Fatty acyls/alkyls are assigned based on their mass as C-atoms:DBE, upon proof for double bond as C-atoms:DB. Number of oxygen-atoms are separated by a semi-colon, e.g. C-atom:DBE;O.
DB-positions are indicated acc. to Δ-nomenclature in a pair of parentheses (geometry unknown), e.g. FA 18:2(9,12), or the number followed by geometry (Z for cis, E for trans), e.g. FA 18:2(9Z,12Z).
A functional group assignment is separated from the C-atom:DBE by a semi-colon, e.g. FA 20:4;OH. If more than one of the same, inside a pair of parentheses, e.g. FA 20:4;(OH)2. These parentheses apply also to NO2 and NH2 functional groups.
A triple bond (Y), once identified, is not counted as DBE, but considered as functional group. Its assignment is separated from the C-atom:DBE by a semi-colon, e.g. FA 16:0;Y. If more than one of the same, inside a pair of parentheses, e.g. FA 10:1;(Y)2.
Functional group-positions are indicated acc. to Δ-nomenclature in front of functional group abbreviation separated by a comma, e.g. FA 20:3(5Z,13E);11OH,15OH;9oxo.
Triple bond-positions are indicated acc. to Δ-nomenclature in front of the Y abbreviation separated by a comma, e.g. FA 16:0;6Y or FA 10:1(8Z);4Y,6Y.
Cyclic structures cyA:B (A=number of ring atoms, B=number of C=C double bonds) are presented in a pair of brackets in front of all other functional groups. Within the brackets, range of ring positions separated by a hyphen, followed by cyA:B annotation, and then by functional groups on the ring structure, e.g. FA 20:2;[8-12cy5:0;11OH;9oxo];15OH.
Known carbohydrate sequences are separated by a hyphen. Unknown sequences are shown in alphabetic order, followed by their number if more than one in front of the lipid backbone, e.g. Gal2GlcCer 18:1;O2/16:0.
Acyl-linkages (N- and/or O-) are annotated by C-atoms:DBE inside a separate pair of parentheses with proven position in front, e.g. Cer 18:1;O2/26:0;26O(FA 18:2).
Alkyl-linkages (N- and/or O-) are annotated by C-atoms:DBE inside a separate pair of parentheses with proven position in front, e.g. FA 18:1(12Z);9O(16:1) for an ether lipid.
Proven stereochemistry is shown after respective functional groups/side-chains in a pair of brackets [R] or [S], e.g. FA 20:4(6Z,8E,10E,14Z);5OH[S],12[R] (= common name LTB4).