Insights into the Photodegradation of the Contact Allergen Fragrance Cinnamyl Alcohol: Kinetics, Mechanism, and Toxicity

Junji Wu; Yanpeng Gao; Teng Guo; Na Luo; Guiying Li; Taicheng An

doi:10.1002/etc.5156

Insights into the Photodegradation of the Contact Allergen Fragrance Cinnamyl Alcohol: Kinetics, Mechanism, and Toxicity

Environ Toxicol Chem. 2021 Oct;40(10):2705-2714. doi: 10.1002/etc.5156. Epub 2021 Aug 20.

Authors

Junji Wu¹, Yanpeng Gao^{1

2}, Teng Guo¹, Na Luo¹, Guiying Li^{1

2}, Taicheng An^{1

2}

Affiliations

¹ Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, China.
² Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Key Laboratory of City Cluster Environmental Safety and Green Development, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, China.

PMID: 34255880
DOI: 10.1002/etc.5156

Abstract

Fragrances can cause general health issues, and special concerns exist surrounding the issue of skin safety. Cinnamyl alcohol (CAL) is a frequent fragrance contact allergen that has various toxic effects on indiscriminate animals. In the present study, the photodegradation transformation mechanism of CAL and toxicity evolution during this process were examined. The results showed that CAL (50 μM) can be completely degraded after 90-min ultraviolet (UV) irradiation with a degradation rate of 0.086 min^-1 . Increased toxicity on bioluminescent bacteria was observed during this process, with lethality increasing from 10.6% (0 min) to 50.2% (90 min) under UV light irradiation. Further, the photodegradation mechanisms of CAL were explored to find the reason behind the increased toxicity observed. Laser flash photolysis and quenching experiments showed that O₂^•- , ¹ O₂ , and ^• OH were mainly responsible for CAL photodegradation, together with ³ CAL* and e_aq^- . The 5 main photodegradation products were cinnamyl aldehyde, benzaldehyde, benzenepropanal, cinnamic acid, and toluene, as identified using gas chromatography-mass spectrometry and liquid chromatography-quadrupole-time-of-flight-mass spectrometry. Once exposed to air, CAL was found to be easily oxidized to cinnamyl aldehyde and subsequently to cinnamic acid by O₂^•- - or ¹ O₂ -mediated pathways, leading to increased toxicity. Benzaldehyde exhibited bioreactive toxicity, increasing the toxicity through ^• OH-mediated pathways. Theoretical prediction of skin irritation indicated that cinnamyl aldehyde (0.83), benzenepropanal (0.69), cinnamyl aldehyde (0.69), and benzaldehyde (0.70) were higher than CAL (0.63), which may cause a profound impact on an individual's health and well-being. Overall, the present study advances the understanding of the photodegradation processes and health impacts of fragrance ingredients. Environ Toxicol Chem 2021;40:2705-2714. © 2021 SETAC.

Keywords: Cinnamyl alcohol; Fragrance ingredient; Laser flash photolysis; Photodegradation; Toxicity evaluation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aldehydes
Allergens / toxicity
Animals
Kinetics
Odorants*
Perfume* / chemistry
Perfume* / toxicity
Photolysis
Propanols

Substances

Aldehydes
Allergens
Perfume
Propanols
cinnamyl alcohol