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Basic nitrogen compounds (mostly heterocyclic) occurring mostly in the plant kingdom (but not excluding those of animal origin). Amino acids, peptides, proteins, nucleotides, nucleic acids, amino sugars, and antibiotics are not normally regarded as alkaloids. By extension, certain neutral compounds biogenetically related to basic alkaloids are included.
Aglycons of anthocyanins; they are oxygenated derivatives of flavylium (2-phenylchromenylium) salts. Cf. flavonoids.
Plant pigments of the flavonoid class; they are glycosides that on hydrolysis yield coloured aglycons called anthocyanidins.
Oxazol-5(4H)-ones (I), compounds derived by cyclisation of N-acyl ![[alpha]](../greek/ALPHA.GIF)
-amino carboxylic acids, RC(=O)NHCR2C(=O)OH, through formal loss of the elements of water. 4-Hydrocarbylideneazlactones (II) are often referred to as 'unsaturated azlactones'.
4-(2-Aminoethyl)pyrocatechol [4-(2-aminoethyl)benzene-1,2-diol] and derivatives formed by substitution.
1,3-Diphenylpropenone (benzylideneacetophenone) and its derivatives formed by substitution. ArCH=CHC(=O)Ar.
cyclodepsipeptides: See depsipeptides.
Intermolecular esters formed from two or more molecules of the same or different phenolic benzoic acids. Depending on the number of the component units, di-, tri-, etc. depsides may result. E.g. 
4-O-galloylgallic acid.
Natural or synthetic compounds having sequences of amino and hydroxy carboxylic acid residues (usually -amino and -hydroxy acids), commonly but not necessarily regularly alternating. In cyclodepsipeptides, the residues are connected in a ring. Cf. carboxylic acids.
Derivatives of the dimethylisoalloxazine (7,8-dimethylbenzo[g]pteridine-2,4(3 H,10H)-dione) skeleton, with a substituent on the 10 position. (Riboflavin, having a 10-D-ribityl group, is the most prominent member). CBN, Trivial Names of Miscellaneous Compounds of Importance in Biochemistry, EJB 2, 1-2 (1967), Rule M-6.
flavonoids (isoflavonoids and neoflavonoids):
Flavonoids, isoflavonoids and neoflavonoids are natural products derived from 2-phenylchromen-4-one (flavone), 3-phenylchromen-4-one, and 4-phenylcoumarin, respectively. Derivations include reduction of the 2(3) carbon-carbon double bond (flavanones), reduction of the keto group (flavanols), and hydroxylation at various positions. See also anthocyanins, chalcones.
J.B. Harborne, T. H. Mabry and H. Mabry, The Flavonoids, Chapman & Hall, 1975.
Flavins tightly bound or covalently attached to a protein chain, commonly through the 8-methyl carbon atom.
flavylium salts: See anthocyanidins.
furanocoumarins: An alternative name for furocoumarins.
Derivatives (mostly of natural origin) of the linear furocoumarin skeleton, psoralen, or its angular isomer, angelicin, variously substituted with hydroxy, methoxy, alkyl, or hydroxymethyl groups, among others.
psoralen angelicin
isoflavonoids: See flavonoids.
ketides: See polyketides.
Plant products of low molecular weight formed primarily from oxidative coupling of two p-propylphenol moieties at their ![[beta]](../greek/BETA.GIF)
carbon atoms; products with units coupled in other ways are neolignans. E.g. 
galbacin, a lignan,
(–)-eusiderin, a neolignan
Macromolecular constituents of wood related to lignans, composed of phenolic propylbenzene skeletal units, linked at various sites and apparently randomly.
neoflavonoids: See flavonoids.
neolignans: See lignans.
A prefix meaning 'a few', and used for compounds with a number of repeating units intermediate between those in monomers and those in high polymers. The limits are not precisely defined, and in practice vary with the type of structure being considered, but are generally from 3 to 10. E.g. oligopeptides, oligosaccharides.
oligopeptides:* See oligo and peptides. BNRD, Rule 3AA-11 (p.48).
Amides derived from two or more amino carboxylic acid molecules (the same or different) by formation of a covalent bond from the carbonyl carbon of one to the nitrogen atom of another with formal loss of water. The term is usually applied to structures formed from -amino acids, but it includes those derived from any amino carboxylic acid. BNRD, Rule 3AA-11 (p. 48). See also proteins, retro. Cf. carboxylic acids.
(R may be any organyl group, commonly but not necessarily one found in natural amino acids)
Natural compounds containing alternating carbonyl and methylene groups ("-polyketones"), biogenetically derived from repeated condensation of acetyl coenzyme A (via malonyl coenzyme A), and usually the compounds derived from them by further condensations. Considered by many to be synonymous with the less frequently used terms acetogenins and ketides.
Peptides containing ten or more amino acid residues. BNRD, Rule 3AA-11 (p. 48). See also under peptides.
Naturally occurring and synthetic polypeptides having molecular weights greater than about 10000 (the limit is not precise). See also peptides. BNRD, Rule 3AA-11 (p. 48).
1. A prefix which indicates a shift by one position of all single and double bonds in a conjugated polyene system. GNOC Recom. R-1.2.7.2. It has been applied only to carotenoids (BNRD Rule Carotenoid-9, p. 229) and retinoids (BNRD, Rule Ret. 4.7, p.249). E.g. retro-carotenoids, retro-retinoids.
2. A prefix which indicates the reverse sequence of a peptide. BNRD, Nomenclature and symbolism for amino acids and peptides. Rule 3AA-22.7 (p. 64).
Naturally occurring substances containing a cis-fused tetrahydrochromeno[3,4-b]chromene nucleus. Many rotenoids contain an additional ring. E.g. 
rotenone