- Neoxanthin is a naturally occurring carotenoid pigment that belongs to the xanthophyll subclass of carotenoids, which are oxygenated derivatives of carotenes. With the molecular formula C₄₀H₅₆O₄, neoxanthin is an epoxycarotenoid characterized by the presence of an epoxide group and multiple conjugated double bonds, giving it a distinct yellow-orange coloration. It is primarily found in green leafy vegetables such as spinach, kale, and lettuce, where it plays an integral role in the structure and function of photosynthetic complexes.
- In plants, neoxanthin functions as a key component of the light-harvesting complex, contributing to the efficient capture of light energy for photosynthesis. It helps stabilize protein-pigment complexes in the thylakoid membranes of chloroplasts and acts as an accessory pigment, broadening the spectrum of light wavelengths that plants can use. In addition to light harvesting, neoxanthin serves an essential role in photoprotection, helping to dissipate excess energy and prevent oxidative damage during high light stress. Like violaxanthin, neoxanthin is involved in the xanthophyll cycle and participates in the regulation of non-photochemical quenching (NPQ), although it is not reversibly interconverted in the same way as violaxanthin and zeaxanthin.
- Another critical function of neoxanthin in plants is its role as a precursor in the biosynthesis of abscisic acid (ABA), a vital plant hormone that regulates growth, seed dormancy, and responses to environmental stresses such as drought and salinity. This conversion involves oxidative cleavage of neoxanthin to produce xanthoxin, a direct precursor of ABA, highlighting neoxanthin’s importance in plant development and stress adaptation.
- In terms of human nutrition and health, neoxanthin is less studied than other carotenoids like lutein, β-carotene, or β-cryptoxanthin. It is not a provitamin A carotenoid, meaning it cannot be converted into vitamin A in the body. Nevertheless, in vitro studies suggest that neoxanthin exhibits anti-cancer, anti-inflammatory, and anti-obesity properties. For instance, it has been shown to inhibit the proliferation of certain cancer cell lines and suppress lipid accumulation in adipocytes. These effects are thought to be mediated through modulation of cell signaling pathways and transcription factors involved in inflammation, cell cycle regulation, and lipid metabolism.
- Despite these promising findings, neoxanthin’s bioavailability in humans is quite low. Unlike more abundant and better-absorbed carotenoids, neoxanthin appears to be poorly absorbed in the human digestive tract and is seldom detected in blood plasma. This may be due to its molecular structure, its food matrix context, or limited transport mechanisms in the intestine. As a result, its physiological concentrations in human tissues are generally negligible, and its contributions to systemic antioxidant defenses are considered minimal under typical dietary conditions.
- In summary, neoxanthin is a carotenoid of significant functional importance in the plant kingdom, particularly in light harvesting, photoprotection, and hormonal regulation through its role in ABA biosynthesis. While its direct role in human health remains uncertain due to low bioavailability, early research suggests it may possess beneficial bioactivities that warrant further investigation. A diet rich in leafy greens naturally includes neoxanthin and may offer synergistic health benefits alongside other better-absorbed carotenoids.
