title: Comparison of in vitro metabolism and cytotoxicity of capsaicin and dihydrocapsaicin.
abstract: Capsaicin and dihydrocapsaicin are the major active components in pepper spray products, which are widely used for law enforcement and self-protection. The use of pepper sprays, due to their irreversible and other health effects has been under a strong debate. In this study, we compared metabolism and cytotoxicity of capsaicin and dihydrocapsaicin using human and pig liver cell fractions and human lung carcinoma cell line (A549) in vitro. Metabolites were screened and identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Using liver cell fractions, a novel aliphatic hydroxylated metabolite (m/z 322) was detected to dihydrocapsaicin but no structure was found corresponding to capsaicin. Instead, a novel phase I metabolite of capsaicin, corresponding to the structure of aliphatic demethylation and dehydrogenation (m/z 294) was identified. In addition, two novel conjugates, glycine conjugates (m/z 363 and m/z 365) and bi-glutathione (GSH) conjugates (m/z 902 and m/z 904), were identified for both capsaicin and dihydrocapsaicin. The medium of the exposed A549 cells contained ω-hydroxylated (m/z 322) and alkyl dehydrogenated (m/z 304) forms, as well as a glycine conjugate of capsaicin. As to dihydrocapsaicin, an alkyl dehydrogenated (m/z 306) form, a novel alkyl hydroxylated form, and a novel glycine conjugate were found. In A549 cells, dihydrocapsaicin evoked vacuolization and decreased cell viability more efficiently than capsaicin. Furthermore, both compounds induced p53 protein and G1 phase cell cycle arrest. Usefulness of the found metabolites as biomarkers for capsaicinoid exposures will need further investigations with additional toxicity endpoints.
authors.affiliation: VERIFIN, Finnish Institute for Verification of the Chemical Weapons Convention, Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland. Electronic address: mia.halme@helsinki.fi.
authors.forename: Mia
authors.initials: M
authors.lastname: Halme
authors.affiliation: Research and Development, Centre for Military Medicine, Finnish Defence Forces, P.O. Box 50, FI-00301 Helsinki, Finland; School of Pharmacy/Toxicology, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, Kuopio FI-70211, Finland.
authors.forename: Maija
authors.initials: M
authors.lastname: Pesonen
authors.affiliation: School of Pharmacy/Toxicology, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, Kuopio FI-70211, Finland.
authors.forename: Heta
authors.initials: H
authors.lastname: Salo
authors.affiliation: VERIFIN, Finnish Institute for Verification of the Chemical Weapons Convention, Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland.
authors.forename: Martin
authors.initials: M
authors.lastname: Söderström
authors.affiliation: School of Pharmacy/Toxicology, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, Kuopio FI-70211, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Pasanen
authors.affiliation: School of Pharmacy/Toxicology, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, Kuopio FI-70211, Finland.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Vähäkangas
authors.affiliation: VERIFIN, Finnish Institute for Verification of the Chemical Weapons Convention, Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland.
authors.forename: Paula
authors.initials: P
authors.lastname: Vanninen
mesh_terms: D000818:Animals; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D002212:Capsicum / Q000737:chemistry; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D018689:Sensory System Agents / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity*; D013552:Swine; D053719:Tandem Mass Spectrometry
chemical_list: D018689:Sensory System Agents; D002211:Capsaicin; C012906:dihydrocapsaicin
keywords: Accurate mass measurement; Cell viability; Immunoblotting; LC–MS/MS; Pepper spray