Profiling of Hura crepitans L. latex by ultra-high-performance liquid chromatography/atmospheric pressure chemical ionisation linear ion trap Orbitrap mass spectrometry

Introduction: The phytochemistry of the latex of Hura crepitans L. (Euphorbiaceae), a widespread tree in the Amazonian forest having many uses, is little known. Only huratoxin, a daphnane diterpene orthoester, has been described despite the high pharmacological potential of this kind of compounds. Glucosphingolipids (cerebrosides) are also known to be distributed in Euphorbiaceae latexes. Objective: To tentatively identify daphnanes diterpenes and cerebrosides in the latex of H. crepitans. Methods: An ethanolic extract of the lyophilised latex of H. crepitans was analysed by ultra-high-performance liquid chromatography (UHPLC) coupled with positive and negative atmospheric pressure chemical ionisation high-resolution mass spectrometry (APCI-HRMS) method using a quadrupole/linear ion trap/Orbitrap (LTQ-Orbitrap). Tandem mass spectrometry (MS/MS) spectra were recorded by two different fragmentation modes: collision induced dissociation (CID) and higher-energy collisional dissociation (HCD). Results: The analysis of CID- and HCD-MS/MS spectra allowed to propose fragmentation patterns for daphnane esters and cerebrosides and highlight diagnostic ions in positive and negative ion modes. A total of 34 compounds including 24 daphnane esters and 10 cerebrosides have been tentatively annotated. Among them, 17 daphnane diterpenes bearing one or two acyl chains are new compounds and the cerebrosides are described in the genus Hura for the first time. Conclusion: This study revealed the chemical constituents of the latex of H. crepitans and particularly its richness and chemical diversity in daphnane diterpenes, more frequently encountered in the species of Thymelaeaceae.