Full-Spectrum Analysis of Bioactive Compounds in Rosemary (Rosmarinus officinalis L.) as Influenced by Different Extraction Methods

<i>Rosmarinus officinalis</i> is a potent antioxidant herb rich in polyphenols. Ultra-high-performance liquid chromatography, coupled with electrospray ionization and quadrupole-time of flight mass spectrometry (UHPLC-ESI-QTOF-MS), enables an exhaustive, full-spectrum analysis of the molecular constituents of natural products. The study aimed to develop a rapid UHPLC method to contribute new insights into the phytochemical composition of rosemary and to assess the performance of nine different procedures for extraction. These include fresh tissue homogenization, fresh and dry leaf decoction, and their respective fermentation, Soxhlet extraction, and sonication using water and methanol. Different extraction methods were found to recover quite different groups of polyphenols within 11 min during 20 min of analysis. Soxhlet extraction, yielded very high concentrations of rosmarinic acid (33,491.33 ± 86.29 µg/g), luteolin-7-<i>O</i>-glucoside (209.95 ± 8.78 µg/g), carnosic acid (2915.40 ± 33.23 µg/g), carnosol (22,000.67 ± 77.39 µg/g), and ursolic acid (5144.27 ± 28.68 µg/g). UHPLC-ESI-QTOF-MS enabled the detection of more than 50 polyphenols, including phenolic acids, flavonoids, and terpenoids in the various extracts. Of these, sagerinic acid ([M - H]^-<i>m/z</i> 719.16), salvianolic acid A ([M - H]^-<i>m/z</i> 493.11) and B ([M - H]^-<i>m/z</i> 717.15), and a pentacyclic triterpenoid corosolic acid ([M - H]^-<i>m/z</i> 471.34) were detected for the first time in rosemary. Soxhlet extraction was found to be the most efficient method, followed by dry leaf decoction. The UHPLC-ESI-QTOF-MS methodology for the analysis proved to be very efficient in the identification and characterization of targeted and untargeted bioactive molecules in the rosemary.