De Vaugelade Ségolène, Nicol Edith, Vujovic Svetlana, Bourcier Sophie, Pirnay Stéphane, Bouchonnet Stéphane
Laboratoire de Chimie Moléculaire, Ecole Polytechnique, UMR-9168, 91128, Palaiseau Cedex, France.
EXPERTOX Laboratory, 14 rue Godefroy Cavaignac, 75011 Paris, France.
Rapid Commun Mass Spectrom. 2018 Jun 15;32(11):862-870. doi: 10.1002/rcm.8104.
The present work is devoted to the structural elucidation of by-products issued from the direct ultraviolet-visible (UV-vis) irradiation of dehydroacetic acid (DHA) in solution and in cosmetic emulsion.
Analyses were carried out using gas chromatography coupled with ion trap mass spectrometry and by high-performance liquid chromatography coupled with ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (LC/UHRMS). The potential toxicities of by-products were estimated by in silico calculations based on a QSAR (Quantitative Structure-Activity Relationship) approach and by in vitro bioassays conducted on Vibrio fischeri bacteria.
Three photoproducts were detected by LC/MS while one photoproduct was detected by GC/MS. The first photoproduct (PP1) corresponds to an isomer of DHA while two isomeric compounds correspond to dimeric structures. The oral rat LD of PP1 was evaluated to be 4.5 times lower than that of the parent molecule which classes it in the category 'moderately toxic' on the Hodge and Sterne toxicity classification. In vitro assays on Vibrio fischeri bacteria showed that the global ecotoxicity of the DHA solution increases with irradiation time.
With the exception of one photoproduct, the structures proposed for the photoproducts on the basis of mass spectral interpretation have not been reported in previous studies. All photoproducts, with the exception of dimers, were detected after irradiation in the cosmetic emulsion. This result shows that personal care products containing DHA must be protected from direct sunlight to prevent photodegradation.
本研究致力于阐明脱氢乙酸（DHA）在溶液和化妆品乳液中直接进行紫外可见（UV-vis）照射所产生的副产物的结构。
采用气相色谱-离子阱质谱联用以及高效液相色谱-超高分辨率傅里叶变换离子回旋共振质谱联用（LC/UHRMS）进行分析。基于定量结构-活性关系（QSAR）方法的计算机模拟计算以及对费氏弧菌进行的体外生物测定，对副产物的潜在毒性进行了评估。
通过LC/MS检测到三种光产物，通过GC/MS检测到一种光产物。第一种光产物（PP1）是DHA的一种异构体，另外两种异构体化合物对应二聚体结构。PP1的大鼠经口半数致死剂量经评估比母体分子低4.5倍，根据霍奇和斯特恩毒性分类，将其归类为“中等毒性”类别。对费氏弧菌进行的体外试验表明，DHA溶液的总体生态毒性随照射时间增加。
除一种光产物外，基于质谱解释提出的光产物结构在先前研究中尚未见报道。除二聚体外，所有光产物在化妆品乳液照射后均被检测到。这一结果表明，含有DHA的个人护理产品必须避免阳光直射，以防止光降解。
