Citral is an acyclic monoterpene aldehyde, and being a monoterpene, it is made of two

isoprene Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is an unsaturated hydrocarbon. It is produced by many plants and animals ...

units. Citral is a collective term which covers two geometric isomers that have their own separate names; the ''E''-isomer is named geranial (''trans''-citral) or citral A. The ''Z''-isomer is named neral (''cis''-citral) or citral B. These stereoisomers occur as a mixture, not necessarily racemic; e.g. in essential oil of Australian ginger, the neral to geranial ratio is 0.61.

Occurrence

Citral is present in the oils of several plants, including

lemon myrtle ''Backhousia citriodora'' (common names lemon myrtle, lemon scented myrtle, lemon scented ironwood) is a flowering plant in the family Myrtaceae, genus ''Backhousia''. It is endemic to subtropical rainforests of central and south-eastern Queensl ...

(90–98%), ''

Litsea citrata ''Litsea'' is a genus of evergreen or deciduous trees or shrubs belonging to the laurel family, Lauraceae. The genus includes a large number of accepted species in tropical and subtropical areas of North America and Asia. Characteristics They a ...

'' (90%), '' Litsea cubeba'' (70–85%),

lemongrass ''Cymbopogon'', also known as lemongrass, barbed wire grass, silky heads, Cochin grass, Malabar grass, oily heads, citronella grass or fever grass, is a genus of Asian, African, Australian, and tropical island plants in the grass family. Some ...

(65–85%), lemon tea-tree (70–80%), ''

Ocimum gratissimum ''Ocimum gratissimum'', also known as clove basil, African basil, and in Hawaii as wild basil,Lindera citriodora'' (about 65%), '' Calypranthes parriculata'' (about 62%),

petitgrain Petitgrain () is an essential oil that is extracted from the leaves and green twigs of the bitter orange tree (''Citrus aurantium'' ssp. ''amara'') via steam distillation. It is also known as petitgrain bigarade. Etymology Petitgrain (Fr.: “ ...

(36%), lemon verbena (30–35%), lemon ironbark (26%),

lemon balm Lemon balm (''Melissa officinalis'') is a perennial herbaceous plant in the mint family and native to south-central Europe, the Mediterranean Basin, Iran, and Central Asia, but now naturalised elsewhere. It grows to a maximum height of . The l ...

(11%),

lime Lime commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Botany ...

(6–9%), lemon (2–5%), and orange. Further, in the lipid fraction (essential oil) of Australian ginger (51-71%) Of the many sources of citral, the Australian myrtaceous tree, Lemon Myrtle, Backhousia citriodora F. Muell. (of the family

Myrtaceae Myrtaceae, the myrtle family, is a family of dicotyledonous plants placed within the order Myrtales. Myrtle, pōhutukawa, bay rum tree, clove, guava, acca (feijoa), allspice, and eucalyptus are some notable members of this group. All speci ...

), is considered superior.

Uses

Citral has a strong lemon (citrus) scent and is used as an aroma compound in perfumery. It is used to fortify lemon oil. (Nerol, another perfumery compound, has a less intense but sweeter lemon note.) The aldehydes citronellal and citral are considered key components responsible for the lemon note with citral preferred. It also has pheromonal effects in

acari Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...

and insects. Citral is used in the synthesis of

vitamin A Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably bet ...

, lycopene, ionone, and methylionone, to mask the smell of smoke. The herb Cymbopogon citratus has shown promising insecticidal and antifungal activity against storage pests.

Food additive

Citral is commonly used as a food additive ingredient. It has been tested (2016) in vitro against the food-borne pathogen Cronobacter sakazakii.

Medical exploration

In a report (1997), Citral is mentioned as cytotoxic to P(388) mouse leukaemia cells. It has 'strong' antimicrobial qualities.

Adverse effects

Two studies showed 1–1.7% of people to be

allergic Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...

to citral, with allergies frequently reported. Citral on its own is strongly sensitizing to allergies; the

International Fragrance Association The International Fragrance Association (IFRA) is the global representative body of the fragrance industry. It seeks to represent the collective interests of the industry and promote the safe use of fragrances through regulation. The Association wa ...

recommends that citral only be used in association with substances that prevent a sensitizing effect. Citral has been extensively tested, with no known genotoxicity or

carcinogenic A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...

effect.

References

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External links

MSDS
Flavors Perfume ingredients Monoterpenes Conjugated aldehydes