Phloroglucinol α-Pyrones of Helichrysum arenarium, Helichrysum stoechas and Achyrocline satureioides: Automated UHPLC–Orbitrap–MS Annotation

Phloroglucinol α-pyrones (PG α-pyr) are acylphloroglucinol–α-pyrone conjugates characteristic of Helichrysum and related genera. Helichrysum arenarium, Helichrysum stoechas and Achyrocline satureioides, three medicinal species not yet examined for the class, were analysed by UHPLC–Orbitrap–MS. The spectra were annotated by an automated R workflow that applies the fragmentation rules established for H. italicum to every MS2 spectrum and matches each against a dictionary of 527 expected compounds. The workflow annotated 175 PG α-pyr derivatives in the three samples (151 in H. arenarium, 53 in H. stoechas, and 32 in A. satureioides; 53 of them in more than one sample); with the 58 compounds published for H. italicum, the four species hold 189 PG α-pyr. Six were detected in all four: arzanol, 6-O-desmethylauricepyrone, 23-methyl-6-O-desmethylauricepyrone, 18,18-bis-desmethyl achyroclinopyrone A, a 3-non-alkylated pentanoyl derivative and helipyrone A. H. italicum and H. arenarium contain 153 and 91 µg/g of PG α-pyr (THAP equivalents), dominated by arzanol; H. stoechas (9.3 µg/g) and A. satureioides (3.2 µg/g) are each dominated by one compound, a dehydro-geranyl benzopyran and helipyrone A. Unsupervised clustering of the MS/MS spectra recovered the scaffold and the α-pyrone substituent. The class is common to the four samples; the dominant subclass and the preferred substituents distinguish them.