Table 1.

Structural types of secondary metabolites and known structures.

Class	Number of structures
WITH NITROGEN
Alkaloids	21000
Non-protein amino acids (NPAA)	700
Amines	100
Cyanogenic glucosides	60
Glucosinolates	100
Alkamides	150
Lectins, peptides	2000
WITHOUT NITROGEN
Monoterpenes (incl. iridoids)	2500
Sesquiterpenes	5000
Diterpenes	2500
Triterpenes, steroids, saponins	5000
Tetraterpenes	500
Phenylpropanoids, phenolic acids, coumarins, lignans	2000
Flavonoids, isoflavonoids, anthocyanins, stilbenoids, tannins, xanthones	10000
Polyacetylenes, fatty acids, waxes	1500
Polyketides (quinones, anthraquinones)	750
Carbohydrates, organic acids	400