Glossary – phytochemistry (under construction)

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Lactones – cyclic compounds with a 5- or 6-membered ring in which the chain is closed by ester formation between a carboxyl and a hydroxyl group in the same molecule

Laricitrin – 3’-O-methylmyricetin

Latex – a viscous fluid exuded from the cut surfaces of the leaves and stems, in the strict sense referring to polymers made up of isoprene units in the cis-configuration (i.a. in gutta), stored in laticifers

Lauric acid – a saturated fatty acid

Lectins – a type of sugar-binding proteins

Leucoanthocyanins – see Proanthocyanidins

Leucodelphinidin – a proanthocyanidin

Leucopelargonidin – a colourless compound related to proanthocyanidins

Lignans – colourless, crystalline, solid, dimeric compounds derived from precursors related to those involved in the formation of lignin, i.e. the union of two units of phenylpropane, cinnamic acid, or their derivatives, through their aliphatic side-chains, they occur in chiral forms (as opposed to lignins); lignans are β,β’(8-8’)-linked dimers of cinnamic acid residues or their biogenetic equivalents (diaryl propanoids)

Lignin – a class of polymers formed from mostly C₆-C₃ monomeric units, cinnamic acid, coumarins, that yield three main kinds of lignin building blocks, hence G, H and S units/lignin, and occurring in all plants; the Mäule reaction, in which a reddish colour is obtained after treatment of the plant sample with potassium permanganate, then dilute hydrochloric acid, and then ammonia, signifies presence of syringaldehyde, with the ratio of syringyl to guaiacyl units being less than 2–2.5:1

Limonoids – type of triterpenoid (tetranortriterpenes), bitter compounds, pentacyclic, with a furan ring attached as a side chain

Linamarin – a cyanogenic glucoside; glucoside of acetone cyanohydrin

Linear coumarin – furanocoumarins in which the furan ring is in line with the benz-2-pyrone nucleus, as in psoralen, often phototoxic

Loganin – a route I iridoid

Loline alkaloids – 1-aminopyrrolizidines containing a saturated pyrrolizidine ring, a primary amine at the C-1 carbon, and an internal ether bridge joining two distant ring carbons (C-2 and C-7), present in Fabaceae, Convolvulaceae and endophyte-inhabited Poaceae

Lotaustralin – a cyanogenic glycoside; glucoside of methyl ethyl ketone cyanohydrins

Lupeol – a triterpenoid

Lupin alkaloids – a class of alkaloids frequent in, e.g., Lupinus (Fabaceae); examples of lupin alkaloids are lupinine, lusitanine, sparteine, cytisine, matrine, lamprolobine, angustifoline, albine, rhombifoline, ormosanine, aphylline, aphyllidine, retamine, baptifoline, multiflorine, camoensidine, and panamine

Lupinine – a quinolizidine alkaloid

Lupulones – bitter-tasting β-acids, present in Humulus

Luteolin – a hydroxylated flavone derivative, abundant in leaves and flowers

Luteone – an isoflavone