Colorless carotenoids are naturally occurring compounds found in many fruits and vegetables, and are the biosynthetic precursors of familiar-colored carotenoids such as lycopene and β-carotene. Despite their important biological roles, phytoene and phytofluene have received far less scientific attention because their geometric isomers are difficult to separate and purify in sufficient quantities for detailed investigation. As a result, little has been known about how individual isomers differ in their chemical characteristics and biological activities, limiting their potential development as high-value functional ingredients.
To address this challenge, a research team led by Associate Professor Masaki Honda from the Graduate School of Environmental and Human Sciences, Meijo University, Japan, collaborated with researchers Kento Nakamura and Kazumi Sawada, researchers at Harima Chemicals Group, Inc., Japan. The researchers established an efficient purification strategy to isolate highly pure geometric isomers of phytoene (PT) and phytofluene (PTF), and comprehensively evaluated their structural characteristics, ultraviolet absorption properties, isomerization behavior, antioxidant capacity, and skin-related biological activities. The study was made available online on May 17, 2026, and will be published in Volume 238 of the journal Food Research International on August 31, 2026.
Using high-purity samples, the researchers systematically compared the properties of individual isomers for the first time. Their analyses demonstrated that each isomer possesses distinct ultraviolet (UV) absorption characteristics and exhibits different responses to light- and heat-induced isomerization. Notably, PTF isomers exhibited strong UV-A-shielding capacity, whereas PT isomers efficiently absorbed UV-B radiation, suggesting that combinations of these naturally occurring carotenoids could provide broad-spectrum UV protection. They also evaluated antioxidant activity together with biological functions relevant to skin health, including anti-glycation activity associated with healthy aging and enzyme-inhibitory activities linked to skin pigmentation and elasticity. By combining chemical analyses with biological evaluation, the study provided a comprehensive understanding of how geometric structure influences the functionality of these colorless carotenoids.
“ Our research was inspired by the limited understanding of individual PT and PTF isomers despite their importance as naturally occurring carotenoids,” explains Dr. Honda. “ By successfully isolating highly purified isomers, we were able to uncover significant differences in their UV-shielding, antioxidant, and biological properties that were previously impossible to evaluate accurately ,” adds Nakamura.
Unlike conventional carotenoids that impart yellow, orange, or red coloration, PT and PTF remain essentially colorless while retaining UV-absorbing properties and other beneficial activities. Their ability to absorb UV light while exhibiting antioxidant and skin-related biological activities suggests they could serve as multifunctional ingredients in UV-protective skincare and cosmetic formulations, skincare products, dietary supplements, functional foods, and nutricosmetics. Because they have minimal impact on product color, they may be more readily incorporated into a wide range of commercial formulations than traditional carotenoids.
The findings also highlight the importance of understanding carotenoid functionality at the isomer level rather than treating each compound as a single entity. Such knowledge could enable researchers and manufacturers to select specific isomers that provide desirable biological or physicochemical properties, supporting the development of next-generation natural ingredients for food, cosmetic, and healthcare industries.
“ Understanding how individual geometric isomers contribute to biological function provides an important foundation for designing more effective natural products ,” says Sawada. “ We hope these findings will encourage further research into colorless carotenoids and accelerate their application in health, beauty, and wellness products.”
Overall, this study establishes a comprehensive reference framework for understanding the physicochemical and biological properties of purified PT and PTF isomers. By demonstrating their unique UV-shielding, antioxidant, anti-glycation, and skin-related activities, the research positions these colorless carotenoids as promising candidates for next-generation beauty, wellness, and healthy aging applications. By revealing their isomer-specific characteristics and biological activities, the research expands the scientific understanding of colorless carotenoids and provides a foundation for developing innovative natural ingredients for future functional food and cosmetic applications.
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 in the Graduate School of Environmental and Human Sciences, Meijo University, Japan. He earned his Doctor of Philosophy in Engineering from the Graduate School of Engineering, The University of Shiga Prefecture, in 2016. His research spans analytical chemistry, chemical reaction and process system engineering, and food sciences. He has published 106 research papers and holds 25 patents, reflecting his significant scientific contributions. In recognition of his sustained research excellence and recent research impact, he was named among Elsevier/Stanford University's World's Top 2% Scientists in both the career-long and single-year impact categories in 2025, highlighting his international research impact and academic leadership worldwide.
Funding information
This work was partially supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number JP25K08968 to Masaki Honda and the New Energy and Industrial Technology Development Organization (NEDO) Intensive Support Program for Young Promising Researchers Grant Number 25101247-0 to Masaki Honda.
Food Research International
Experimental study
Cells
Comprehensive characterization of high-purity colorless carotenoid (phytoene and phytofluene) geometric isomers: Spectroscopic properties, isomerization behavior, antioxidant capacity, and biological activities
16-May-2026
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.