Chemical partitioning and utilization potential of Paeonia qiui fruits: α-linolenic acid-rich kernels and bioactive fruit by-products

Tree peonies ( Paeonia sect. Moutan) are valued medicinal and oilseed crops, among which Paeonia qiui remains insufficiently studied despite its close phylogenetic relationship with cultivated medicinal and oilseed species. To explore its utilization value, chemical characteristics and potential bioactivities of different fruit parts of P. qiui were systematically investigated. The results demonstrated that the seed kernels contained elevated levels of α-linolenic acid and other unsaturated fatty acids, confirming their oilseed potential comparable to that of established tree peony oilseed crops. Complementary untargeted and targeted metabolomics revealed a diverse phytochemical composition, with 629 metabolites annotated across seeds and their by-products. Tissue-specific monoterpene glycosides (e.g., paeoniflorin and albiflorin) and stilbenes (e.g., suffruticosol A–D and trans -gnetin H) were identified as characteristic metabolites, preferentially accumulating in seed kernels and seed coats, respectively. Bioactivity evaluation of methanol extracts from each fruit part revealed significant antioxidant activities. Notably, both the fruit pod and seed coat exhibited pronounced bacteriostatic effect against Streptococcus pyogenes and inhibitory effects on anti-neuroinflammatory responses, which were attributed to the tissue-specific phytochemicals. Collectively, this study provides novel insights into the value-added potential of P. qiui fruits, establishing a scientific basis for utilizing kernels as an oil resource and fruit by‑products as sources of characteristic bioactive compounds.