Effect of flavoring chemicals on free radical formation in electronic cigarette aerosols

Zachary T Bitzer; Reema Goel; Samantha M Reilly; Ryan J Elias; Alexey Silakov; Jonathan Foulds; Joshua Muscat; John P Richie Jr

doi:10.1016/j.freeradbiomed.2018.03.020

Effect of flavoring chemicals on free radical formation in electronic cigarette aerosols

Free Radic Biol Med. 2018 May 20:120:72-79. doi: 10.1016/j.freeradbiomed.2018.03.020. Epub 2018 Mar 13.

Authors

Zachary T Bitzer¹, Reema Goel², Samantha M Reilly², Ryan J Elias¹, Alexey Silakov³, Jonathan Foulds², Joshua Muscat², John P Richie Jr⁴

Affiliations

¹ Department of Food Science, Pennsylvania State University, College of Agricultural Sciences, University Park, PA, USA.
² Department of Public Health Sciences, Pennsylvania State University Tobacco Center of Regulatory Science (TCORS), Pennsylvania State University College of Medicine, 500 University Dr., Mail Code: CH69, Hershey, PA 17033, USA.
³ Department of Chemistry, Pennsylvania State University, Eberley College of Science, University Park, PA, USA.
⁴ Department of Public Health Sciences, Pennsylvania State University Tobacco Center of Regulatory Science (TCORS), Pennsylvania State University College of Medicine, 500 University Dr., Mail Code: CH69, Hershey, PA 17033, USA. Electronic address: jrichie@phs.psu.edu.

PMID: 29548792
PMCID: PMC5940571
DOI: 10.1016/j.freeradbiomed.2018.03.020

Abstract

Background: Flavoring chemicals, or flavorants, have been used in electronic cigarettes (e-cigarettes) since their inception; however, little is known about their toxicological effects. Free radicals present in e-cigarette aerosols have been shown to induce oxidative stress resulting in damage to proliferation, survival, and inflammation pathways in the cell. Aerosols generated from e-liquid solvents alone contain high levels of free radicals but few studies have looked at how these toxins are modulated by flavorants.

Objectives: We investigated the effects of different flavorants on free radical production in e-cigarette aerosols.

Methods: Free radicals generated from 49 commercially available e-liquid flavors were captured and analyzed using electron paramagnetic resonance (EPR). The flavorant composition of each e-liquid was analyzed by gas chromatography mass spectroscopy (GCMS). Radical production was correlated with flavorant abundance. Ten compounds were identified and analyzed for their impact on free radical generation.

Results: Nearly half of the flavors modulated free radical generation. Flavorants with strong correlations included β-damascone, δ-tetradecalactone, γ-decalactone, citral, dipentene, ethyl maltol, ethyl vanillin, ethyl vanillin PG acetal, linalool, and piperonal. Dipentene, ethyl maltol, citral, linalool, and piperonal promoted radical formation in a concentration-dependent manner. Ethyl vanillin inhibited the radical formation in a concentration dependent manner. Free radical production was closely linked with the capacity to oxidize biologically-relevant lipids.

Conclusions: Our results suggest that flavoring agents play an important role in either enhancing or inhibiting the production of free radicals in flavored e-cigarette aerosols. This information is important for developing regulatory strategies aimed at reducing potential harm from e-cigarettes.

Keywords: E-cig; E-cigarettes; Electronic cigarette; Flavorants; Flavors; Free radicals; Oxidative stress.

Publication types

Research Support, N.I.H., Extramural
Research Support, U.S. Gov't, P.H.S.

MeSH terms

Aerosols / analysis
Aerosols / chemistry
Electronic Nicotine Delivery Systems*
Flavoring Agents / chemistry*
Free Radicals / analysis*
Propylene Glycol / chemistry*
Solvents / chemistry*

Substances

Aerosols
Flavoring Agents
Free Radicals
Solvents
Propylene Glycol

Grants and funding

P50 DA036107/DA/NIDA NIH HHS/United States