Polyphenolic Complex of Plum Varieties Most Adapted to the Conditions of the Southern Russian Far East: Identification by Tandem Mass Spectrometry

The aim of the study was to isolate and identify a complex of bioactive compounds, including polyphenols and compounds of other chemical classes, from plum fruit pulp extracts in order to assess their potential as a source of biologically active phenolic substances. Ripe fruits of the plum varieties Krasnomyasaya, Neporazhemaya, Long Yuan Mi Li, and Long Yuan Tao Li, collected at the end of July 2023 from the collection variety plot of the Far Eastern Experimental Station (Primorskii Krai), were used as plant material. Fractional maceration was applied to obtain highly concentrated extracts: seven-day infusion of each portion of the pulp in a dark room at room temperature, with three successive extractions for each sample. Mass spectrometric analysis was performed using an ion trap mass spectrometer with an electrospray ionization source (positive and negative ion modes). Multicomponent mixtures were separated on a Shimadzu LC-20 Prominence high-performance liquid chromatograph equipped with a UV detector and a Shodex ODP-40 4E reversed-phase column. A gradient elution mode with a transition from water to acetonitrile was used: 0.40 min (0% acetonitrile), 4.60 min (25% acetonitrile), 60.75 min (100% acetonitrile), and 75.12 min (100% > acetonitrile). Mass spectra were recorded in the m/z range of 100–1700, with fragmentation up to the fourth order. In total, the mass spectrometric experiments have identified 74 chemical compounds, 52 of which have been classified as polyphenols. A large group of anthocyanins and catechins has been identified, indicating pronounced antioxidant properties of the studied plant matrices. For the first time, the polyphenolic compounds ibuprofen, phloretin, umbelliferone, methyl gallic acid, dihydrokaempferol, herbacetin, umbelliferone hexoside, and p-coumaroylquinic acid have been isolated from the pulp of Prunus L. fruits. The results demonstrate the high potential of the fruits of the studied plum varieties as a source of biologically active polyphenolic substances that may be used in the development of new drugs and biologically active additives.