A comparative study of chemical variations and antioxidant activities in three Osmanthus taxa across different plant parts, seasons, and species

As the flower of Osmanthus fragrans has been widely used as perfume and food, the chemical constituents and bioactivities of the other plant parts of O. fragrans and related species have drawn the interest of researchers. In the present study, we performed a comparative analysis of the LC-MS-based chemical profiles and antioxidant activity of three Osmanthus taxa occurring in Korea, Osmanthus fragrans var. aurantiacus (OFA), Osmanthus × fortunei (OF), and Osmanthus heterophyllus (OH). Leaves and twigs were analyzed for all three taxa, whereas flowers were analyzed only for OFA and OF. To highlight the effect of the harvesting time on chemical profiles and bioactivity, twigs and leaves were collected monthly from May to October, while flowers were collected in September, from the same individual for each taxon. Distinct metabolite distributions were observed among plant parts and taxa, with flavonoids enriched in leaves and phenylethanoid glycosides enriched in twigs. Seasonal variation influenced the abundance of apigenin derivatives in leaves and calceolarioside B, chlorogenic acid, and 10-hydroxyligustrolide in twigs. Antioxidant assays revealed relatively high activity in twig extracts, and bioactivity-based molecular networking along with experimental validation identified acteoside-type phenylethanoids as potential contributors to antioxidant activity. These results highlight the tissue- and season-related chemical diversity of three Osmanthus taxa and provide a basis for their further application as natural antioxidant resources.