Β-Cyclocitral

β-Cyclocitral (beta-cyclocitral) is an apocarotenoid derived from the C7 oxidation of β-carotene. This apocarotenoid has revived interest due to its roles in plant development. β-cyclocitral has been found endogenously in a variety of organisms including plants, cyanobacteria, fungi and animals.^[2] β-Cyclocitral is a volatile compound that contributes to the aroma of various fruits, vegetables and ornamental plants.^[3] In plants, β-cyclocitral was found to be an important regulator in root development.^[4]

β-Cyclocitral

Names
IUPAC name 2,6,6-Trimethylcyclohexene-1-carbaldehyde
Other names 1-Formyl-2,6,6-trimethyl-1-cyclohexene
Identifiers
CAS Number	432-25-7
3D model (JSmol)	Interactive image
Beilstein Reference	2042086
ChEBI	CHEBI:53177
ChEMBL	ChEMBL1952257
ChemSpider	9511
ECHA InfoCard	100.006.439
EC Number	207-081-3
PubChem CID	9895
UNII	77Y0U2X29G
CompTox Dashboard (EPA)	DTXSID7047142
InChI InChI=1S/C10H16O/c1-8-5-4-6-10(2,3)9(8)7-11/h7H,4-6H2,1-3H3 Key: MOQGCGNUWBPGTQ-UHFFFAOYSA-N
SMILES CC1=C(C(CCC1)(C)C)C=O
Properties
Chemical formula	C10H16O
Molar mass	152.237 g·mol−1
Boiling point	62–63 °C (144–145 °F; 335–336 K)
Solubility in water	86.14 mg/L
Hazards
GHS labelling:[1]
Pictograms
Signal word	Warning
Hazard statements	H302, H312, H315, H319, H332, H335
Precautionary statements	P261, P264, P264+P265, P270, P271, P280, P301+P317, P302+P352, P304+P340, P305+P351+P338, P317, P319, P321, P330, P332+P317, P337+P317, P362+P364, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Application

β-Cyclocitral is used as an analytical standard for the determination of volatile organic compounds in saffron due to its analog structure to safranal.

Because β-cyclocitral is associated with cyanobacteria death, it is an analyte that can be tracked in bodies of water to monitor cyanobacteria blooms.^[5]

It has also been found to promote the growth of roots in rice, prompting its consideration as a potential agricultural tool.^[6]

Biosynthesis

The biosynthesis of β-cyclocitral relies on the formation of β-carotene through the isoprenoid biosynthetic pathway underpinning carotenoid formation. Similar to other apocarotenoids, the formation of β-cyclocitral can occur via the enzymatic and non-enzymatic oxidative cleavage of double bonds in β-carotene.^[7] For β-cyclocitral to form, the cleavage of C7-C8 double bonds are needed. While no enzyme has been identified to have high specificity for the production of β-cyclocitral, a carotenoid cleavage dioxygenase (CCD4) has been identified as being capable of cleaving β-carotene at the needed position.^[8] 13-lipoxygenase (LOX2) has also been identified to cleave β-carotene at the C7 position.^[9] β-cyclocitral can also be formed from the direct oxidation of β-carotene by reactive oxygen species, especially singlet oxygen (¹O₂). In plants, ¹O₂ is mainly produced from excited chlorophylls in the reaction center of PSII where β-carotene serves to quench the reactive oxygen species.^[10]

β-Cyclocitral biosynthesis