title: Mass Spectrometric Discrimination of Squalene Monohydroperoxide Isomers.
abstract: Squalene (SQ), a main component of human sebum, is readily photooxidized by exposure to sunlight, producing six squalene monohydroperoxide (SQ-OOH) isomers. Despite its known connection to various skin conditions, few studies have sought to analyze SQ-OOH at the isomeric level. In this study, we aimed to develop a method to discriminate each SQ-OOH isomer with the use of tandem mass spectrometry (MS/MS). The six standard SQ-OOH isomers were prepared by photooxidizing SQ in the presence of rose bengal, a photosensitizer, and isolated by semipreparative high-performance liquid chromatography (HPLC). To purify each isomer, 2-methoxypropene, which reversibly reacts with the hydroperoxide group of SQ-OOH, was utilized. Product ion scanning was then performed on the standard SQ-OOH isomers in the absence and presence of the sodium ion. In the absence of the sodium ion, the fragmentation patterns produced by atmospheric pressure chemical ionization were similar between the isomers, whereas in the presence of the sodium ion by electrospray ionization, unique fragmentation patterns were achieved. Based on these fragment ions, HPLC-MS/MS multiple reaction monitoring analysis was conducted on a mixture of the standard SQ-OOH isomers. We achieved discrimination of SQ-OOH isomers with high selectivity and detected SQ-OOH isomers at nanogram levels. These results may improve our understanding of the effect of SQ-OOH on skin conditions as well as the mechanism behind SQ peroxidation.
authors.affiliation: Food and Biodynamic Chemistry Laboratory, Graduate School of Agricultural Science, Tohoku University.
authors.forename: Naoki
authors.initials: N
authors.lastname: Shimizu
authors.forename: Hannah
authors.initials: H
authors.lastname: Bersabe
authors.forename: Junya
authors.initials: J
authors.lastname: Ito
authors.forename: Shunji
authors.initials: S
authors.lastname: Kato
authors.forename: Ryo
authors.initials: R
authors.lastname: Towada
authors.forename: Takahiro
authors.initials: T
authors.lastname: Eitsuka
authors.forename: Shigefumi
authors.initials: S
authors.lastname: Kuwahara
authors.forename: Teruo
authors.initials: T
authors.lastname: Miyazawa
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Nakagawa
mesh_terms: D002851:Chromatography, High Pressure Liquid; D007536:Isomerism; D008054:Lipid Peroxides / Q000032:analysis* / Q000138:chemical synthesis; D017319:Photosensitizing Agents / Q000737:chemistry; D012395:Rose Bengal / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D013185:Squalene / Q000031:analogs & derivatives* / Q000032:analysis* / Q000138:chemical synthesis; D053719:Tandem Mass Spectrometry; D014466:Ultraviolet Rays
chemical_list: D008054:Lipid Peroxides; D017319:Photosensitizing Agents; D012395:Rose Bengal; D013185:Squalene; D012964:Sodium