ζ-Carotene, a key intermediate in lycopene biosynthesis, is widely found in plants and photosynthetic microorganisms, but its isomer-specific properties remain poorly understood due to isolation and purification challenges. Researchers have now developed a purification strategy to obtain high-purity geometric isomers and systematically characterized, for the first time, their isomer-specific spectral properties, photoisomerization behavior, UV-shielding capacity, antioxidant activity, and skin-related biological activities—highlighting ζ-carotene's promise as a natural ingredient for skin health and photoprotection.
ζ-Carotene is a naturally occurring carotenoid found in edible plants and photosynthetic microorganisms, where it functions as a key intermediate in lycopene biosynthesis. Previous studies have suggested that ζ-carotene-containing materials may help alleviate oxidative stress and inflammatory responses and may contribute to the maintenance of skin health. These findings have increased interest in ζ-carotene as a potential ingredient in ingestible and topical skincare products.
However, despite its biological relevance and potential applications, the intrinsic physicochemical properties and biological activities of ζ-carotene remain poorly understood. This knowledge gap is largely attributable to its relatively low abundance in natural sources and the difficulty of obtaining highly purified ζ-carotene, particularly as individual geometric isomers.
To mitigate the existing knowledge gap, a team of researchers from Japan, led by Associate Professor Masaki Honda from Meijo University, successfully separated and purified four major geometric isomers of ζ-carotene, all- E -, 9 Z , 9 Z ,9′ Z , and 9 Z ,13 Z ,9′ Z . The purified isomers were used to analyze their structural, spectroscopic, antioxidant, and biological properties. Dr. Mitsuya Ito, Dr. Kazumi Sawada, and Dr. Kento Nakamura from Harima Chemicals, Japan, were collaborators in the research team. Their research was made available online on June 18, 2026, and was published in Volume 74 of Journal of Agricultural and Food Chemistry on July 01, 2026.
“The separation, purification, and functional assessment of carotenoid geometric isomers have long piqued the interest of our research team. Although carotenoids like lycopene and astaxanthin have been shown to exhibit isomer-dependent features, nothing was known about the properties of specific ζ-carotene isomers. In order to investigate their potential as novel functional ingredients, we worked on extracting highly purified ζ-carotene isomers and elucidated their distinct physicochemical and biological characteristics,” explained Dr. Honda and Dr. Nakamura while talking about the motivation behind the study.
The team used normal-phase chromatography to successfully separate the four ζ-carotene isomers, which were subsequently isolated, purified, and structurally characterized by nuclear magnetic resonance analysis. They then investigated the stability of these compounds when exposed to light, which revealed a unique photoisomerization pattern. Exposure to white LED light rapidly shifted all isomers toward a steady chemical mixture, dominated by the 9 Z isomer, demonstrating a distinctive response to light. While prolonged illumination caused gradual degradation, the carotenoids remained comparatively stable during storage in the dark at 30 °C. This highlighted the need for photoprotection more than temperature control for maintaining ζ-carotene-based product stability, which can guide the manufacture, storage, and quality control of these products.
Detailed spectroscopic analyses further revealed the UV-A-shielding capacity of these compounds, suggesting that ζ-carotene could function as an effective natural UV filter. The study also established reference spectral parameters that can facilitate future identification and quantitative analysis of ζ-carotene in biological and industrial samples.
Unlike the deep orange-red color associated with well-known carotenoids such as lycopene and β-carotene, ζ-carotene exhibited a much lighter yellow appearance. This softer coloration suggests that ζ-carotene could offer photoprotective benefits while contributing only minimal color when incorporated into foods, dietary supplements, or skincare products.
The study also revealed several biologically relevant activities of ζ-carotene associated with skin protection. The predominant 9 Z and 9 Z , 9′ Z isomers efficiently quenched singlet oxygen, one of the major reactive oxygen species generated during UV exposure, along with hydroxyl radical scavenging activity. They also markedly inhibited the formation of fluorescent glycation end products, implicated in skin aging and tissue damage.
Dr. Sawada and Dr. Ito highlighted the significance of the study: “The food, cosmetic, and healthcare industries are seeing a growing demand for natural, multifunctional ingredients that protect products and promote health. The findings from our study provide fundamental scientific evidence that supports using ζ-carotene as a high-value natural ingredient, offering practical insight for its production, storage, and utilization in next-generation functional foods, dietary supplements, and cosmetics.”
In conclusion, the study findings lay the critical groundwork for future studies exploring how ζ-carotene functions in biological systems, serving as an important roadmap for researchers investigating carotenoid chemistry, stability, and bioactivity. Beyond the lab, the compound shows massive commercial promise as a naturally derived UV-A filter in sunscreens and skincare lines. Due to its potent antioxidant and anti-glycation properties, the compound can soon become a staple ingredient in healthy-aging products, nutricosmetics, and dietary supplements designed to protect and promote skin health.
About Meijo University
Meijo University traces its origin back to the establishment of the Nagoya Science and Technology Course in 1926, giving it a proud history of more than 90 years. As one of the largest universities in the Chubu region, Meijo University is a comprehensive learning institution that supports a wide range of academic fields from the humanities to physical sciences. With a network of more than 200,000 graduates and alumni, it strives to contribute not only to local industries but also to international communities in various fields. Meijo University is also known as the birthplace of the carbon nanotube. To foster the human resources of the next generation, the university continues to tackle ongoing challenges by further enhancing its campus and creating new faculties.
Website: https://www.meijo-u.ac.jp/english/
About Harima Chemicals Group, Inc.
Founded in 1947, Harima Chemicals Group, Inc. is a leading global manufacturer of pine chemical products and functional materials derived from natural resources. Leveraging its expertise in forest-based chemistry, the company develops and supplies a wide range of products for applications in food, cosmetics, adhesives, electronic materials, papermaking, and industrial products. Through continuous innovation and sustainable utilization of renewable resources, Harima Chemicals Group contributes to the creation of environmentally friendly products and solutions that support healthier and more sustainable lifestyles worldwide. The company actively promotes research and development in functional ingredients, including carotenoids and other naturally derived bioactive compounds, to address emerging needs in the health, beauty, and wellness sectors.
Website: https://www.harima.co.jp/en/
About Associate Professor Masaki Honda from Meijo University
Dr. Masaki Honda is an Associate Professor at the Faculty of Science and Technology and the Graduate School of Environmental and Human Sciences, Meijo University, Japan. He earned his Ph.D. in Engineering from the University of Shiga Prefecture. His research focuses on food science, particularly carotenoids, polyphenols, lipid chemistry, isomerization, and supercritical fluid processing technologies. Dr. Honda’s work bridges fundamental chemistry and practical applications, advancing the development of functional food ingredients and sustainable processing methods. He has authored more than 100 peer-reviewed publications.
Funding information
This study was partially supported by JSPS KAKENHI Grant Number 25K08968. (9 Z , 9′ Z )-ζ-Carotene was obtained as a result of the project supported by the New Energy and Industrial Technology Development Organization (NEDO), conducted by the Research Institute of Innovative Technology for the Earth (RITE) and Harima Chemicals Group, Inc. (B&I Vol.83 No.3, 2025).
Journal of Agricultural and Food Chemistry
Experimental study
Not applicable
Spectral Characterization, Isomerization Behavior, and Antioxidant Activity of ζ‑Carotene Geometric Isomers: From Biosynthetic Intermediates to Functional Ingredients
1-Jul-2026
The authors declare no competing financial interest.