In recent years, caffeic acid and its derivatives have received increasing attention due to their obvious physiological activities and wide distribution in nature. In this paper, to clarify the status of research on plant-derived caffeic acid and its derivatives, nuclear magnetic resonance spectroscopy data and possible biosynthetic pathways of these compounds were collected from scientific databases (SciFinder, PubMed and China Knowledge). According to different types of substituents, 17 caffeic acid and its derivatives can be divided into the following classes: caffeoyl ester derivatives, caffeyltartaric acid, caffeic acid amide derivatives, caffeoyl shikimic acid, caffeoyl quinic acid, caffeoyl danshens and caffeoyl glycoside. Generalization of their ¹³C-NMR and ¹H-NMR data revealed that acylation with caffeic acid to form esters involves acylation shifts, which increase the chemical shift values of the corresponding carbons and decrease the chemical shift values of the corresponding carbons of caffeoyl. Once the hydroxyl group is ester, the hydrogen signal connected to the same carbon shifts to the low field (1.1~1.6). The biosynthetic pathways were summarized, and it was found that caffeic acid and its derivatives are first synthesized in plants through the shikimic acid pathway, in which phenylalanine is deaminated to cinnamic acid and then transformed into caffeic acid and its derivatives. The purpose of this review is to provide a reference for further research on the rapid structural identification and biofabrication of caffeic acid and its derivatives.

Glucose and lipid metabolism disorders are the core pathological mechanism of a variety of metabolic diseases, and the incidence of related diseases is increasing year by year, which seriously threatens human life and health. Traditional Chinese medicine with medicinal and edible properties refers to Chinese medicinal resources that have both medicinal and edible characteristics. Due to its safety and its health-promoting and medicinal functions, traditional Chinese medicine has received increasing attention in the development of functional health foods. Phenolic acids are important secondary metabolites that are ubiquitous in medicinal and edible homologous plants, and the regulation of glycolipid metabolism is an important activity and plays a key role in many diseases. In this paper, we focus on the alleviation of glycolipid disorders using MEHH phenolic acids, which regulate glucose metabolism and lipid metabolism, improve insulin resistance, inhibit inflammatory responses, alleviate oxidative stress, and regulate intestinal flora; additionally, we summarize the mechanism in order to provide a reference for MEHH phenolic acids in the treatment of glycolipid metabolism diseases.

Increased S100 calcium-binding protein A9 (S100A9)-related signals have been reported in selected hepatic and ocular inflammatory settings. This structured narrative review evaluates S100A9-related species as candidate participants in hepato–ocular crosstalk. Across human, ocular fluid, animal, and cellular studies, the available findings provide context-specific support for disease-associated hepatic expression and ocular responsiveness, with stronger evidence for selected local S100A9–Toll-like receptor 4 (TLR4)-associated effects than for S100A9-specific receptor for advanced glycation end products (RAGE) signaling. Clinical associations involving metabolic dysfunction-associated steatotic liver disease, diabetic retinopathy, chronic liver disease, dry eye disease, and uveitis are heterogeneous and confounded. Interpretation is further limited by the non-equivalence of S100A9, S100A8/A9, calprotectin, and higher-order complexes. Current evidence, therefore, suggests that S100A9-related species may serve as exploratory indicators of inflammatory activity or contribute to local inflammatory amplification in selected settings, rather than acting as established liver-derived causal signals. Future studies should prioritize analyte-specific measurement, source tracing, and selective perturbation. S100A9 is best regarded as a testable candidate node within a broader metabolic–inflammatory network.