Glossary – phytochemistry (under construction)

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Imbricatonol – a naphthol naphthoquinone dimer, derived from the oxidative coupling of dianellidin with stypandrone or by the incomplete oxidation of stypandrol

Imidazole – an aromatic heterocyclic alkaloid (diazole)

Indane – a hydrocarbon (benzocyclopentane) with the formula C9H10 (e.g. barbeyol)

Indole alkaloids – alkaloids that contain an indole ring, derived from phenylalanine or tryptophane

Inolizidine – a polyhydroxy alkaloid

Inositol – cyclohexane-1,2,3,4,5,6-hexol; cyclohexane polyol (a sugar) present in nine stereoisomers (e.g. myo-inositol or cis-1,2,3,5-trans-4,6-cyclohexanehexol)

Inulin – a fructan that acts as a storage polysaccharide in many asterids, yields fructose on hydrolysis

Ipecoside – an isoquinoline alkaloid

Iridoids – subclass of terpenoids; monoterpenoids with lactone substitutions, usually in glycosidic form, in nearly all deoxyloganic acid or epi-deoxyloganic acid is an intermediary; iridoids are formed from two isopentane (isoprene) units, and they are cyclic C10 compounds, usually with an O in one ring; iridoids are produced by the mevalonate pathway and formed in two main ways: route I (secoiridoids) or route II (carboxylated and decarboxylated iridoids); far more than 600 different structures are known; iridoids may be classified into 13 groups:

Group-1-iridoids – 8-C-skeleton iridoids

Group-2-iridoids – 9-C-skeleton iridoids

Group-3-iridoids – 10-C-skeleton iridoids

Group-4-iridoids – iridoid aglycones

Group-5-iridoids – bis-iridoids and bis-iridoid aglycones

Group-6-iridoids – valeriana iridoids

Group-7-iridoids – plumeria iridoids

Group-8-iridoids – miscellaneous iridoid-like compounds

Group-9-iridoids – simple secoiridoids

Group-10-iridoids – terpene-conjugated iridoids (e.g. verbascoside)

Group-11-iridoids – phenolic-conjugated iridoids

Group-12-iridoids – bis-secoiridoids

Group-13-iridoids – miscellaneous secoiridoids

Isoflavanones – 3-aryl-chroman-4-ones; isoflavanones are precursors for numerous complex molecules, e.g. pterocarpans and rotenones, and have a wide range of biological activities

Isoflavans – isomeric form of flavones with the most reduced structure of any isoflavonoids that lack hydroxyl or ketone groups, i.e. there are no oxygens in the structure; they are frequent as phytoalexins in Fabaceae

Isoflavones – class of flavonoids in which the B-ring of flavones is attached to the 3-position (instead of the 2-position), absorbing light in the ultraviolet region and a component of ‘bee violet’

Isoflavonoids – class of flavonoids in which the B-ring of flavones is attached to the 3-position (instead of the 2-position) and that lack the 3-hydroxy group of flavonols; isoflavonoid compounds include, e.g., genistein, daidzein (isoflavones), formononetin, ferrerein, pachyrrhizin, coumestrol, rotenone, munduserone, and angolensin

Isokestose – oligosaccharides, inulin trisaccharide, the building block of inulin type fructans

Isopentenyl pyrophosphate – the building unit of terpenes

Isoprene – 2-methyl-1,3-butadiene; a volatile unsaturated branched chain five-carbon hydrocarbon (hemiterpenoid) which is the basic unit of terpenes, synthesized via the mevalonic acid pathway

Isoquinoline alkaloids – type of true alkaloids, formed from a precursor of 3,4-dihydroxytyramine (dopamine) linked to an aldehyde or ketone

Isorhamnetin – an O-methylated flavonol

Isoshinanolones – acetogenic tetralones (ketone derivatives of tetralin) present in Dioncophyllaceae

Isothiocyanates – esters of isothiocyanic acid, R-N=C=S, mustard oils, with a pungent smell and a sharp taste, derived from glucosinolates undergoing an enzymatic reaction (via the enzyme myrosinase) when plant tissue is crushed

Isovitexin – apigenin-6-C-glucoside; a glycoflavone