Phytochemical Characterization and Antioxidant Activity of Syringa L. Leaves and Bark as Potential Sources of Useful Phytochemicals

The genus Syringa L. (Oleaceae) comprises plant species widely cultivated for ornamental purposes and traditionally used in medicine, with reported anti-inflammatory, analgesic, and antioxidant properties. This study aimed to evaluate and compare the phytochemical composition and antioxidant potential of bark and leaf extracts from selected Syringa species (S. vulgaris, S. × henryi, S. amurensis, S. josikaea, S. oblata, S. persica, and S. pubescens). Secondary metabolites were qualitatively profiled and tentatively identified using liquid chromatography–mass spectrometry (LC-MS), while total phenolic, flavonoid, and phenolic acid contents were determined using spectrophotometric assays. Antioxidant potential was assessed using the ABTS radical scavenging assay. The results demonstrated significant interspecific and organ-dependent variability in phytochemical composition and antioxidant activity. Bark samples were generally characterized by higher levels of total phenolics and phenolic acids, whereas leaves accumulated higher levels of flavonoids. Among the evaluated taxa, S. pubescens leaves and S. oblata emerged as the most promising samples, displaying high levels of bioactive metabolites and strong antioxidant potential, in some aspects exceeding those observed for the well-known S. vulgaris. In contrast, S. × henryi showed lower chemical diversity and bioactivity. Overall, the findings indicate that selected Syringa species represent valuable sources of bioactive phenolic metabolites with antioxidant potential and may serve as promising candidates for advanced chemical, mechanistic, and safety evaluation for further pharmaceutical and cosmetic applications.