Secondary metabolites are low-molecular-weight organic compounds produced by plants under specific conditions. While they are not directly involved in fundamental growth and developmental processes, they play crucial roles in plant defense, protection, and regulation. These compounds mainly include phenolics, terpenoids, alkaloids, flavonoids, and others. Light, as a key environmental factor regulating the synthesis of plant secondary metabolites, influences their production and accumulation through multidimensional regulatory mechanisms. Different light qualities activate or suppress specific metabolic pathways via signal transduction networks mediated by specialized photoreceptors. Light intensity dynamically modulates secondary metabolite accumulation by affecting photosynthetic efficiency, while photoperiod coordinates metabolic rhythms through circadian clock genes. These light responsive mechanisms constitute a chemical defense strategy that enables plants to adapt to their environment, while also providing critical targets for the directed regulation of medicinal components and functional nutrients. This study provides a review of recent research on the effects of light on plant secondary metabolites, aiming to deepen the understanding of the molecular mechanisms underlying light-regulated secondary metabolism. The findings may offer an insight for enhancing bioactive compounds in medicinal plants and developing functional agricultural products.

Fever is caused by an increase in the heat production process when the body is under the action of a heat source or the dysfunction of the temperature center. Ellagic acid (EA) is a polyphenol dilactone that has anti-inflammatory, anti-tumor, and antioxidant activities. Male Sprague-Dawley rats were injected yeast to reproduce an experimental fever model (150 ± 20 g), and the rectal temperature and its change values were subsequently taken 19 h later; the excessive production of interleukin-1β (IL-1β) and prostaglandin2 (PGE2) induced by yeast was regulated to normal by EA administration. Rat brain metabolomics investigation of pyrexia and the antipyretic anti-inflammatory effect of EA was performed using Ultra-High-Performance Liquid Chromatography–Mass spectrometry (UPLC-MS). Twenty-six metabolites, as potential biomarkers, significantly altered metabolites that were found in pyretic rats, and eleven metabolites, as biomarkers of the antipyretic mechanism of EA, were significantly adjusted by EA to help relieve pyrexia, which was involved in glycerophospholipid metabolism and sphingolipid metabolism, etc. In conclusion, potential metabolic biomarkers in the brain shed light on the mechanism of EA’s antipyretic effects, mainly involving metabolic pathways, which may contribute to a further understanding of the therapeutic mechanisms of fever and therapeutic mechanism of EA.

The goal of this study was to identify and compare the main biomarkers of Taxillus chinensis from different hosts. A metabolomics approach utilizing ultra-pressure liquid chromatography coupled with tandem mass spectrometry (UPLC-MS), including cluster analysis, sample correlation analysis and orthogonal partial least squares discriminant analysis, was used to explore the flavonoid metabolites of Taxillus chinensis growing on different hosts. Results: The total flavonoids content (up to 30.08 mg/g) in Taxillus chinensis from Morus alba (CSG) was significantly higher than that from growth on Liquidambar formosana (CFG) or Clausena lansium (CHG) (p < 0.01). There were 23 different metabolites between CSG and CHG, 23 different metabolites between CSG and CFG, and 19 different metabolites between CHG and CFG. The results demonstrated that different hosts exerted a large influence on the metabolites of Taxillus chinensis; it was found that CSG differed from CFG and CHG in eleven metabolic compounds, ten of which were upregulated and one of which was downregulated. Most of these metabolites derive from compounds contained in the host plant, white mulberry (Morus alba); many feature potent anti-cancer effects. Differences in host can influence the type and abundance of flavonoids in parasitic plants such as Taxillus chinensis, which is of great significance to researchers seeking to understand the formation mechanism of Taxillus chinensis metabolites. Therefore, attention should be paid to the species of host plant when studying the Taxillus chinensis metabolome. Plants grown on Morus alba offer the greatest potential for the development of new anti-cancer drugs.

Ellagic acid (EA) is a polyphenol dilactone that has been reported to have antipyretic, anti-inflammatory, anti-tumor, and antioxidant activities, but the mechanism of action has not been reported. In this study, serum metabolomics was used to explore the mechanism of EA on rat fever induced by beer yeast, and to screen out marker metabolites to provide a reference for the antipyretic effect of EA. The acute fever model of male Sprague Dawley rats involved subcutaneous injection with 20% aqueous suspension of yeast (15 mL/kg) in their back. At the same time of modeling, EA was given orally by 10 mL/kg intragastric administration for treatment. During the experiment, the temperature and its change values of rats were recorded, and Interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF-α), Prostaglandin E2 (PGE2), Cyclic Adenosine Monophosphate (cAMP), Superoxide Dismutase (SOD) and Malondialdehyde (MDA)—six physiological and biochemical indexes of rats—were detected after the experiment. In addition, the hypothalamus of each rat was analyzed by Western blot (WB), and the levels of Phospho Nuclear Factor kappa-B (P-NF-κB P65) and IkappaB-alpha (IKB-α) were detected. Then, the serum metabolites of rats in each group were detected and analyzed by gas chromatograph mass spectrometry and the multivariate statistical analysis method. Finally, when screening for differential metabolites, the potential target metabolic pathway of drug intervention was screened for through the enrichment analysis of differential metabolites. Pearson correlation analysis was used to systematically characterize the relationship between biomarkers and pharmacodynamic indicators. EA could reduce the temperature and its change value in yeast induced fever rats after 18 h (p < 0.05). The level of IL-6, TNF-α, PGE2, cAMP, SOD and MDA of the Model group (MG) increased significantly compared to the Normal group (NG) (p < 0.001) after EA treatment, while the levels of the six indexes in the serum and cerebrospinal fluid of yeast-induced rats decreased. The administration of yeast led to a significant increase in Hypothalamus P-NF-κB P65 and IKB-α levels. Treatment with EA led to a significant decrease in P-NF-κB P65 levels. Moreover, combined with VIP > 1 and p < 0.05 as screening criteria, the corresponding retention time and characteristic mass to charge ratio were compared with the NIST library, Match score > 80%, and a total of 15 differential metabolites were screened. EA administration significantly regulated 9 of 15 metabolites in rat serum. The 15 differential metabolites involved linoleic acid metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, galactose metabolism, biosynthesis of unsaturated fatty acids and glycerolipid metabolism. Pharmacodynamic correlation analysis was conducted between 15 different metabolites and six detection indexes. There was a significant correlation between 13 metabolites and six detection indexes. D-(−)-lactic acid, glycerin, phosphoric acid, 5-oxo-L-proline were negatively correlated with TNF-α, and p values were statistically significant except for L-tyrosine. In addition, glycerin was negatively correlated with IL-6, PGE2 and MDA, while phosphoric acid was negatively correlated with IL-6. In conclusion, EA may play an antipyretic anti-inflammatory role through the inhibition of the IKB-α/NF-κB signaling pathway and five metabolic pathways, which may contribute to a further understanding of the therapeutic mechanisms of the fever of EA.

Objectives: Kajiichigoside F1 and rosamultin are natural triterpenoid saponins found in the root of Rosa laevigata Michx. These compounds are isomers, making their separation challenging. Nonetheless, they have been reported to exhibit significant anti-inflammatory activity, although their mechanism of action remains unclear. This study aimed to optimize the extraction process of echinacoside and rosamultin from R. laevigata and to elucidate the anti-inflammatory mechanisms of these saponins in an LPS-induced acute lung injury (ALI) model. Methods: The extraction process was optimized using a single-factor experiment and the Box–Behnken response surface methodology, with the content of kajiichigoside F1, rosamultin, and their total content serving as evaluation indices. The acute lung injury model was induced by LPS, and lung tissue damage was assessed through hematoxylin and eosin (HE) staining. The secretion of relevant inflammatory factors was quantified using enzyme-linked immunosorbent assay (ELISA), and the expression levels of associated proteins were analyzed via Western blotting. Results: The optimal extraction conditions were determined to be an ethanol volume fraction of 80.0%, a solid–liquid ratio of 1:25, an extraction duration of 80 min, and three extraction cycles. Kajiichigoside F1 and rosamultin were found to mitigate alveolar inflammation in mice with acute lung injury (ALI) by effectively reducing the expression of the pro-inflammatory cytokines TNF-α and IL-6. Additionally, these compounds down-regulated the expression of phosphorylated NF-κB p65 and NF-κB IκBα proteins, thereby alleviating inflammatory symptoms. Conclusions: Kajiichigoside F1 and rosamultin attenuate the inflammatory response in acute lung injury induced by lipopolysaccharide (LPS) stimulation through modulation of the NF-κB signaling pathway. This study preliminarily elucidates their anti-inflammatory mechanism, suggesting that both compounds possess therapeutic potential for ALI. These findings provide significant guidance for the future development of active components derived from the root of R. laevigata and establish a foundation for enhancing the quality standards of its medicinal materials.

Acute liver failure (ALF) is characterized by a rapid decline in liver function, leading to metabolic and organ failure. This study employed liver metabolomics, Nuclear Factor kappa-B (NF-κB) signaling pathway analysis, and inflammatory factor profiling to investigate the therapeutic mechanisms of xanthoxylin in ALF. Xanthoxylin administration led to increased antioxidant levels and reduced markers of inflammation and tissue damage. Xanthoxylin downregulated the messenger RNA (mRNA) expression of Nitric Oxide Synthase (NOS), Interleukin-1β (IL-1β), Interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF-α), NF-κB, Inhibitor of NF-κB α (IκBα), and Toll-like receptor 4 (TLR4), and inhibited the protein expression of p-p38 and p-p65 while upregulating B-cell CLL/Lymphoma 2 (Bcl-2) and B-cell Lymphoma-x (Bcl-xl). Metabolomic analysis identified 41 differentially expressed metabolites, 20 of which showed strong correlations with pharmacodynamic parameters. These 20 candidate metabolite signatures are involved in amino acid and carboxylic acid metabolic pathways, with potential links to glycolysis and the tricarboxylic acid (TCA) cycle. Together, these findings suggest that xanthoxylin exerts therapeutic effects against ALF by modulating the IκBα/NF-κB signaling pathway and related metabolic pathways, providing a scientific basis for understanding its multi-target mechanism.