9cisviolaxanthin

9-cis-violaxanthin is a cis isomer of violaxanthin, a xanthophyll carotenoid found in photosynthetic organisms. Like violaxanthin, it is a C40 carotenoid with a polyene chain and oxygen-containing functional groups, but its defining feature is the cis configuration at the double bond between carbon 9 and carbon 10, giving a bent rather than linear conformation compared with the all-trans form.

Occurrence and abundance tend to vary by species and tissue. 9-cis-violaxanthin has been detected in plants and algae, typically in smaller amounts than all-trans violaxanthin and other major xanthophylls. Its quantity can be influenced by light exposure, developmental stage, and environmental conditions. Some cis isomers can form during extraction or analysis if samples are not protected from light and heat.

Biological context and function are not fully established. The canonical xanthophyll cycle in plants involves violaxanthin, antheraxanthin, and zeaxanthin, mediated by violaxanthin de-epoxidase and zeaxanthin epoxidase. 9-cis-violaxanthin is not considered a central substrate of this cycle, but cis isomers of violaxanthin may arise as minor forms that could affect pigment–protein interactions or photoprotective responses in ways that are not yet well understood.

Analytical notes: identification and quantification are typically performed by high-performance liquid chromatography with spectroscopic detection, sometimes supported by mass spectrometry. The pigment shows absorption properties distinct from the all-trans form due to the cis double bond.

See also: xanthophyll cycle, violaxanthin, antheraxanthin, zeaxanthin.