Glossary – phytochemistry (under construction)

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Galactans – a cell wall storage polysaccharide in which galactose is the main sugar, belonging to the matrix of pectins

Galactitol – see Dulcitol

Galactomannans – hemicelluloses containing galactose and mannose

Galactose – a hexose sugar, isomer of glucose, giving rise to galacturonic acid

Galactosides – glycosides containing galactose; α-galactosides have their glycosidic bond above the plane of the galactose molecule; β-galactosides have their glycosidic bond below the plane of the galactose molecule

Galacturonic acid – derivative of galactose

Gallic acid – 3,4,5- trihydroxybenzoic acid, when esterified with a carbohydrate, gallic acid contributes to the formation of gallotannins, a type of hydrolyzable tannin

Gentisic acid – 2,5-dihydroxybenzoic acid, derivative of benzoic acid and a product of the break-down of aspirin; gentisic acid is produced by carboxylation of hydroquinone

Geraniin – a cytotoxic hydrolyzable ellagitannin

Geraniol – a monoterpenoid alcohol

Germacranes – cyclic compounds having two methyl groups and one isopropyl group

G-lignin – referring to a kind of lignin in which there are a major percentage of guaicyl units – coniferyl is the alcohol – and that is found mostly in gymnosperms, especially conifers

Glucitol – see Sorbitol

Glucose – a hexose sugar forming a six-membered ring, in the alpha form with the -OH group at the C₁ position below the plane of the molecule, and in the beta form with the -OH group at the C₁ position above the plane of the molecule

Glucosides – a glycoside in which the sugar constituent is glucose (originally the term glucoside was used whatever the sugar involved)

Glucosinolates – mustard oil glycosides, mostly colourless, with a sharp, odour, which via hydrolysis with myrosine yield isothiocyanates or mustard oils

Glucurono-arabinoxylans – arabinoxylan or pentosan; the main component of hemicelluloses in the cell wall

Glycine betaines – see Betaines

Glycoflavones – class of flavonoids which have a sugar attached, often C-glycosyl

Glycosides – any compound that contains a carbohydrate molecule (sugar) that is convertible by hydrolysis into the sugar and a non-sugar component (aglycone), named for the sugar involved, as glucoside (glucose is the sugar), fructoside (fructose), etc.

Gossypetin – 8-hydroxyflavonoid, a yellow flavonoid

Gossypol – a bis-terpenoid

Griselinoside – an iridoid glucoside

Gums – complex water-soluble polysaccharide chains; non-crystalline mixtures of sugars and organic acids

Gutta – gutta percha; similar to latex, but made up of isoprene units in trans-position, trans-1,4-polyisoprene

Gynocardin – a cyclopentenoid cyanogenic glycoside