Chemical Composition and Biological Activities of Torreya grandis Kernels: Characteristics of Polymethylene-Interrupted Fatty Acids and Polyphenolic Compounds and Their Potential Health Effects

Torreya grandis kernels, with their long cultivation history and significant economic value, have gained attention for their characteristic chemical components. This review systematically evaluates recent research on the chemical constituents and biological activities of T. grandis kernels. The key highlights include the following. (1) Chemical composition: This review details their unique fatty acid profile, particularly the high content of unsaturated fatty acids and rare polymethylene-interrupted polyunsaturated fatty acids such as sciadonic acid. It also examines polyphenolic compounds (flavonoids, phenolic acids, and biflavonoids like kayaflavone) and volatile components dominated by D-limonene. Other constituents, such as proteins, amino acids, vitamins, and minerals, are covered. Advanced analytical techniques (Gas Chromatography–Mass Spectrometry, GC-MS; Liquid Chromatography–Tandem Mass Spectrometry, LC-MS/MS) for component identification are discussed. (2) Biological activities: This review summarizes the major biological activities of T. grandis kernel extracts and key components. These include antioxidant effects (via the polyphenol-mediated NF-E2-related factor 2 (Nrf2) pathway), anti-inflammatory properties (via polymethylene-interrupted polyunsaturated fatty acids, PMI-PUFAs, inhibition of 5-LOX, and polyphenol regulation of NF-κB), and cardiovascular protection (potentially involving the AMPKα/SREBP-1c pathway). Research on gut microbiota regulation and enzyme inhibition is also outlined. (3) Research gaps and prospects: This review critically analyzes the limitations in the current research, including mechanism elucidation, component interactions, bioavailability, and safety assessment (especially the lack of human studies). Future research directions should focus on multiomics integration, structure–activity relationship analysis, standardization, and rigorous clinical evaluation. This review provides a theoretical reference for understanding the scientific value of T. grandis kernels and promoting their sustainable development.