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Selenium nanoparticles (SeNPs) can be absorbed by plants, thereby affecting plant physiological activity, regulating gene expression, and altering metabolite content. However, the molecular mechanisms by which exogenous selenium affects Polygonatum kingianum coll.et Hemsl plant secondary metabolites remain unclear. In this study, we exposed P. kingianum plants to SeNPs at 0, 10, 25, and 50 mg/L concentrations. Joint physiological, metabolomic, and transcriptomic analyses were performed to reveal the response mechanisms of major secondary metabolites of P. kingianum to SeNPs. Our data shows that under the treatment of 25 mg/L, the photosynthetic electron transfer rate of plants significantly increases and the carbon-nitrogen ratio significantly decreases. In parallel, the main active components, polysaccharides and saponins, showed a significant increase in content, while flavonoid content decreased. SeNPs affect polysaccharide accumulation mainly through up-regulation of SPS, UGPase, AGPase, UTP, and SUS genes in starch and sucrose metabolic pathways. The accumulation of saponins was affected by upregulating genes in the sesquiterpenoid and triterpenoid biosynthesis pathways, including PAD, ADH, PK, and GS. The accumulation of flavonoids was mainly regulated by metabolic pathways such as flavonoid biosynthesis, isoflavonoid biosynthesis, and the biosynthesis of phenylpropanoids. In summary, this study reveals the key metabolic pathways affected by SeNPs in the main secondary metabolic products of P. kingianum .

Objectives: Polygonatum kingianum is a medicinal herb used in various traditional Chinese medicine formulations. The polysaccharide fraction of P. kingianum can reduce insulin resistance and restore the gut microbiota in a rat model of aberrant lipid metabolism by down regulating miR-122. The aim of this study was to further elucidate the effect of P. kingianum on lipid metabolism, and the roles of specific miRNAs and the gut microbiota. Key findings: P. kingianum administration significantly altered the abundance of 29 gut microbes and 27 differentially expressed miRNAs (DEMs). Several aberrantly expressed miRNAs closely related to lipid metabolism were identified, of which some were associated with specific gut microbiota. MiR-484 in particular was identified as the core factor involved in the therapeutic effects of P. kingianum . We hypothesize that the miR-484- Bacteroides/Roseburia axis acts as an important bridge hub that connects the entire miRNA-gut microbiota network. In addition, we observed that Parabacteroides and Bacillus correlated significantly with several miRNAs, including miR-484, miR-122-5p, miR-184 and miR-378b. Summary: P. kingianum alleviates lipid metabolism disorder by targeting the network of key miRNAs and the gut microbiota.

Polysaccharides are the primary active constituents of Polygonatum kingianum Coll. et Hemsl. However, the comprehensive characterization of P . kingianum polysaccharides (PKP) remains scarce, impeding investigations into the structure–activity relationship. In this study, a novel polysaccharide, PKP1, was purified using Cellulose DE-52 and Sephadex G-50 column chromatography, and its complete structure was elucidated through monosaccharide composition analysis, methylation analysis, as well as 1D and 2D NMR analysis. The results revealed that PKP1 primarily comprised Fru and Glc, exhibiting a molecular weight of 5.3 × 10 3  Da and a polymer dispersity index of 1.20. The completed structure of PKP1 consisted of β-D-Fru f -(2 → , → 1,2)-β-D-Fru f -(6 → , → 1)-β-D-Fru f -(2 → and → 1)-α-D-Glc p -(6 → as the main chain sugar residues, with β-D-Fru f -(2 → and → 2)-β-D-Fru f -(6 → serving as the side chains sugar residues. The detailed structure of PKP1 suggested it is a novel Fru-dominated neutral polysaccharide. Biological assays indicated that PKP1 significantly reduced the levels of NO, IL-6, and TNF-α in RAW264.7 macrophages, while also exerting regulatory effects on the gut microbiota structure and its metabolites in vitro. Our findings enriched the understanding of the structural characteristics of P . kingianum polysaccharides and laid a solid foundation for considering P . kingianum as a potential functional food supplement. Graphical Abstract