Temporal Accumulation Patterns of Paeonol, Paeoniflorin, and Tannic Acid in Leaves of Five Tree Peony (Paeonia suffruticosa) Cultivars

As a significant by-product of the tree peony industry, tree peony leaves are a valuable source of bioactive compounds, making the analysis of their composition and accumulation patterns vital for exploitation. This study systematically investigated the temporal accumulation patterns of three bioactive compounds—paeonol, paeoniflorin, and tannic acid—in the leaves of five major tree peony cultivars ('Luoyanghong', 'Fengdan', 'Jingyu', 'Erqiao', and 'Huhong') across different growth stages in Henan, China. Using HPLC and UV-Vis methods, we quantified the contents of these components at five key harvest timepoints from March to September. The results revealed distinct temporal dynamics. Paeoniflorin content decreased sharply after flowering, with reductions of 70%-80% by September compared to March levels across all cultivars. Paeonol accumulation was cultivar-dependent, generally peaking in May-July; for instance, 'Jingyu' reached 761.48 µg/g in July, while 'Fengdan' showed a declining trend from 554.05 µg/g in March. Tannic acid content was highest in spring (e.g., 'Luoyanghong' at 643.98 mg/g in April), then declined significantly by autumn, with reductions of 50%-60% across cultivars. These findings demonstrate significant temporal and varietal variations in bioactive compound accumulation in tree peony leaves. The study provides a scientific basis for optimizing harvest timing to maximize the yield of specific compounds, supporting the valorization of tree peony leaf resources in pharmaceutical and functional product applications.