Lily-of-the-Valley

The plant

Lily-of-the-valley (Convallaria majalis) is a Eurasian woodland plant. It grows to 15-35 cm (6-14 in) tall and produces racemes of pendulous, bell-shaped white flowers. Flowering is in late spring, typically May to June in Britain. The plant is used in floristry.

It is a herbaceous perennial that often forms extensive colonies by spreading underground stems called rhizomes. Each stem carries two, rarely three, leaves that are 5-20 cm (2-8 in) long and 3-7 cm (1-3 in) broad. The flowering stems bear a one-sided raceme of six to twelve pendulous flowers on the upper part of the stem. Each flower has six white tepals, rarely pink, fused at the base into a bell with reflexed tips, and measures 5-10 mm (0.2-0.4 in) across. The berry holds an average of 3.9 large whitish to brownish seeds, persists for an average of 47.5 days, and averages 85.8% water. In the APG III system the genus is placed in the family Asparagaceae, subfamily Convallarioideae, a group formerly treated as the family Ruscaceae.

Toxic constituents

The plant is highly poisonous if consumed, because of its concentration of potent cardiac glycosides (cardenolides). The fruit is a poisonous small orange-red berry approximately 5-7 mm (0.2-0.3 in) in diameter. Convallatoxin is a natural cardiac glycoside found in the plant. Convallatoxin has the formula C₂₉H₄₂O₁₀ and a molar mass of 550.645 g/mol. It inhibits the Na+,K+-ATPase, as other digitalis-like compounds do. Its therapeutic index is very small, so the margin between a therapeutic dose and an overdose is narrow.

Aroma chemicals of the muguet note

Hydroxycitronellal derives from citronellal and belongs to the class of organic compounds known as medium-chain aldehydes. Lilial is a trade name for lily aldehyde, also known as lysmeral or lilestralis. It was once produced synthetically on a multi-ton scale for use as a perfume in cosmetic preparations and laundry powders. Like most aldehydes, Lilial tends to oxidize on storage.

Bourgeonal is an aromatic aldehyde used in perfumery. It is a colorless liquid, although commercial samples can appear yellow. Hydroxymethylpentylcyclohexenecarboxaldehyde (HMPCC) is a synthetic fragrance known by the trade names Lyral, Kovanol, Mugonal and Landolal. It is found in some soaps, eau de toilettes, aftershaves and deodorants. Lyral is known to act as a skin allergen.

Chemical data of the main aroma chemicals

Hydroxycitronellal is 7-hydroxy-3,7-dimethyloctanal; its formula is C₁₀H₂₀O₂, its molar mass 172.26 g/mol and its density 0.922 g/cm³. Its condensation product with indole is called Indolene, and its Schiff base with methyl anthranilate is called Aurantiol.

Lilial is 3-(4-tert-butylphenyl)-2-methylpropanal, an aromatic aldehyde with the formula (CH₃)₃CC₆H₄CH₂CH(CH₃)CHO and a molar mass of 204.313 g/mol. It occurs naturally in crow-dipper and tomato plants. It is a clear viscous liquid with a density of 0.94 g/cm³, a melting point of -20 °C and a boiling point of 275 °C. It dissolves in water only to 0.045 g/L at 20 °C and has a log P of 4.36. It is also used as an intermediate in the synthesis of the agrochemicals fenpropimorph and fenpropidin.

Bourgeonal is 3-(4-tert-butylphenyl)propanal, with the formula (CH₃)₃CC₆H₄CH₂CH₂CHO, a molar mass of 190.286 g/mol, a density of 0.938 g/cm³ and a boiling point of 265.1 °C. As of 2010, bourgeonal is the only known odor substance to which males have a higher average sensitivity than females.

HMPCC has the preferred IUPAC name 4-(4-hydroxy-4-methylpentyl)cyclohex-3-ene-1-carbaldehyde, the formula C₁₃H₂₂O₂, a molar mass of 210.317 g/mol and a density of 0.995 g/mL at 20 °C. It is commonly tested for in patients undergoing patch testing.