Chromatographic analyses and unambiguous identification of atranol‐like secondary metabolites in oakmoss absolute

Abstract

Oakmoss is a commercially significant natural extract used in exotic perfumes, cosmetics, and other personal care products. Unfortunately, oakmoss absolutes and oils also contain atranol and chloroatranols, well‐known potent skin sensitizers, and hence, their levels in personal care products are regulated. To address the presence of these metabolites and unravel the similar metabolites in the oakmoss absolute, two independent analytical methods were developed. As a proof of concept, one commercial absolute oakmoss was analyzed with complementary, orthogonal LC/MS, GC/MS methods and further confirmed with MS2 experiments. Sixteen secondary metabolites, including atranols, were identified by both GC and LC analyses. Many of the identified components appear to be the precursors of the atranols or process artifacts. One atranol analog, in particular, isopropyl haematommate, was investigated extensively with electron ionization mass spectrometry to show that fragmentation spectra can be applied for the unambiguous identification of related compounds. An intriguing fragmentation pattern was observed for a typical α‐hydroxybenzoate, involving sequential loss of alkene, alkanol, water, or carbon monoxide. A similar fragmentation pattern has been observed with ESI; however, the loss of CO2 was dominant, while the loss of CO was most commonly observed with the EI system independent of substituents on the aromatic ring. The identification of these metabolites was further confirmed with pure standards. Even though many of these unique secondary metabolites are structurally similar to atranols, their skin sensitization potential is unknown; hence, the developed methods can serve as an effective tool to assess the overall quality of various oakmoss‐based products.