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Updated: Apr 21, 2026

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
Published on: February 7, 2022
Photosensitized E/Z isomerization of (all-E)-lycopene aiming at practical applications
Masaki Honda1, Haruyuki Igami, Takahiro Kawana
1Research and Development Division, Kagome Company, Ltd. , Nishitomiyama, Nasushiobara 329-2762, Japan.
Abstract:
Photoisomerization of (all-E)-lycopene to the corresponding Z-isomers was investigated under visible to middle-infrared light irradiation in the presence of several sensitizers, including edible ones. Highly purified (all-E)-lycopene from tomato paste was isomerized to Z-isomers to the extent of 46.4-57.4% after irradiation with the sensitizers for 60 min in acetone, in which a thermodynamically stable isomer of (5Z)-lycopene was predominantly generated, whereas kinetically preferable (9Z)- and (13Z)-lycopenes were dominant without sensitizer. Examination of the time course of photoisomerization demonstrated that the highest isomerization efficiency (80.4%) was attained using erythrosine as the sensitizer under 480-600 nm light irradiation in hexane for 60 min, a protocol that successfully suppressed the degradation of lycopene. (5Z)-Lycopene, reported as a more bioavailable isomer, was again predominantly produced with erythrosine and rose bengal in each solvent.
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