Journal of Analytical Toxicology, 2021;45:739–747 doi:https://doi.org/10.1093/jat/bkaa150 Advance Access Publication Date: 17 October 2020 Article Article Does Eumelanin Oxidation Play a Role on the Photostability of Ethyl Glucuronide in Hair Exposed to Simulated Solar Radiation? Giorgia Miolo 1, * , Benedetta Vicario 1 , Giulia Stocchero 2 , Valerio Causin 3 , Susanna Vogliardi 1 and Donata Favretto 2, * 1 Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, 35131, Italy; 2 Legal Medicine and Toxicology, University Hospital of Padova, Padova, 35121, Italy and 3 Department of Chemical Sciences, University of Padova, Padova, 35131, Italy *Author to whom correspondence should be addressed. Email: giorgia.miolo@unipd.it donata.favretto@unipd.it Abstract The action of solar radiation on the concentration of the ethanol metabolite ethyl glucuronide (EtG) in 40 hair samples of nonabstinent subjects was investigated. Hair samples of different colors were analyzed before and after irradiation with artifcial sunlight under a light dose corresponding to 3 months of sun exposure. After irradiation, an increase of EtG concentration was detected in 55% of the samples ranging from 5% to 141%. In 16 cases, a concentration reduction ranging from −2% to −74% was observed. The measure of the level of pyrrole-2,3,5-tricarboxylic acid (PTCA), a marker of eumelanin oxidation, demonstrated the largest increase in oxidation in light brown hair where the greatest degradation of EtG was observed after irradiation. However, the rise of PTCA in all hair tested was accompanied by increase in EtG concentration in 8/10 samples and by decrease in 2/10, suggesting no correlation between the two markers. To verify if hair structure was modifed by light, scanning electron microscopy (SEM) analysis was performed on irradiated hair of different colors and compared with the dark samples. SEM revealed modifcation of hair structure in all samples showing partial shaft exfoliation and reduction of hair thickness under the treatment with solar radiation. Introduction The evaluation of alcohol consumption through the use of appro- priate biomarkers is a fundamental tool to know, prevent and contain the phenomenon of excessive chronic drinking and its social consequences. Common biochemical indicators of alcohol use are the mean corpuscular volume, and the hepatic enzymes gamma glutamyl trans- ferase, alanine aminotransferase and aspartate aminotransferase. However, the increase of enzyme levels suffers from sensitivity and diagnostic specifcity as they are infuenced by individual patho- physiological conditions such as liver disease, drug therapies and hormonal factors. More recent indicators of alcohol use are ethyl glucuronide (EtG), ethyl sulfate (EtS) and ethyl esters of fatty acids (FAEE), which are metabolites deriving from phase II metabolism of the ethanol molecule. EtG in particular is considered a direct marker of alcohol abuse with absolute specifcity, not affected by the possible presence of liver pathologies, unlike more traditional markers. Physiologically, the formation of EtG is due to the conju- gation of ethanol with activated glucuronic acid in the presence of uridindifosfato (UDP) glucuronyl transferase. EtG detection helps to identify either chronic or acute intake, due to its wide detec- tion window, depending on the different biological samples. EtG can be detected in serum for a few hours after drinking, when ethanol is no more present in blood, whereas its determination in © The Author(s) 2020. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com 739 Downloaded from https://academic.oup.com/jat/article/45/7/739/5924261 by guest on 28 December 2022