Hazelnut is one of the four major nuts in the world and has high nutritional and economic value. This study employed Illumina sequencing of ITS rDNA and 16S rRNA genes to identify the seasonal changes in soil microbial community, the predominant environmental factors driving microbial community composition, and the differences in soil microbial composition among different species of the genus Corylus. We found that the soil microbial community composition of species of Corylus changed significantly with the change in seasons. Corylus heterophylla and Corylus kweichowensis had more ectomycorrhiza in their soil compared to Corylus avellane. The main factor influencing fungal community composition in soil was the available potassium, while that of bacteria was the total phosphorus content. Co-occurrence network analysis revealed that the ratio of positive interaction to negative interaction in soil of C. heterophylla and Ping’ou (C. heterophylla × C. avellane) was higher, while the negative interaction of soil community structure in C. avellane was greater. The bacterial community was more stable than the fungal community according to microbial diversity and co-occurrence network analyses. The findings of this research may facilitate improvements to the production and soil system management in hazel planting processes.

This study investigates the antioxidant behaviors of a hazelnut tetrapeptide, FSEY (Phe-Ser-Glu-Tyr), in an oil-in-water emulsion. The emulsion was prepared with stripped hazelnut oil at a ratio of 10%. O/W emulsions, both with and without antioxidants (FSEY and TBHQ), were incubated at 37 °C. The chemical stabilities, including those of free radicals and primary and secondary oxidation productions, along with the physical stabilities, which include particle size, zeta-potential, color, pH, and ΔBS, were analyzed. Consequently, FSEY displayed excellent antioxidant behaviors in the test system by scavenging free lipid radicals. Both primary and secondary oxidation products were significantly lower in the FSEY groups. Furthermore, FSEY assisted in stabilizing the physical structure of the emulsion. This antioxidant could inhibit the increase in particle size, prevent the formation of creaming, and stabilize the original color and pH of the emulsion. Consequently, FSEY may be an effective antioxidant additive to use in emulsion systems.

Ping’ou hybrid hazelnut is one of the most profitable tree nuts in China, but economically important cultivars must first be genetically validated to meet industrial demand. Traditional approaches used for cultivar identification are mainly trait-based and unreliable. Previous approaches at the DNA level, focusing on the identification of species or/and varieties that originated in China, were not used widely in hybrid hazelnut because there was no proper standard sample. In this research, a multiplexed fingerprinting test was conducted to allow for hazelnut cultivar identification using SSR markers derived from European hazelnut. Twenty-seven SSR markers were used to fingerprint 57 genetically unique Ping’ou hybrid hazelnut and related wild species. All markers showed a high level of polymorphism, as indicated by mean values for observed heterozygosity (H_o = 0.84), expected heterozygosity (H_e = 0.80), and polymorphism information content (PIC = 0.78). A total of 301 alleles were detected, and the number of effective alleles varied from 6 for KG817 and GB818 to 18 for B654, with an average of 11.2 alleles per locus. Moreover, the Shannon’s information index (I) ranged from 1.293 for BR215 to 2.385 for B654, with an average of 1.908. The neighbor-joining tree, principal coordinate analysis, and Bayesian analysis revealed clear separation between hybrid cultivars and wild forms (Cluster/group I), as well as the differentiation within hybrid genotypes (Clusters/groups II and III). Additionally, the NJ dendrogram demonstrated a further split within Clusters/group III (III a and III b). Altogether, with the comparable SSR information of the European hazelnut cultivar ‘Barcelona’, the newly developed marker sets can assist in the germplasm identification of hazelnut cultivars and reproductive materials. Importantly, these combined SSR loci can be applied to characterize the genetic relationships and population structures among wild genotypes and hybrid cultivars, which will then provide information to guide hazelnut breeding based on their genetic background.

Background/Objectives: Emerging evidence suggests that hippocampal neuroinflammation (HNF) drives cognitive decline via dysregulation of the microbiota-gut-brain axis. Corylus heterophylla Fisch. male flower extract (CFE), a flavonoid-rich by-product of hazelnut processing, presents a promising yet unexplored neuroprotective candidate. This study investigated the preventive effects and mechanisms of CFE against HNF-induced cognitive decline. Methods: In the present study, mice were pretreated with CFE (200 mg/kg) before the Lipopolysaccharide (LPS) administration. Cognitive function, inflammation, core pathology, neuroplasticity, gut microbiota and serum metabolites were assessed. The chemical composition of CFE was analyzed by UHPLC-MS and its direct immunomodulatory effects were investigated in BV2 cells. Results: Behavioral assessments demonstrated significant therapeutic efficacy. This was evidenced by the recovery from hippocampal damage, accompanied by reduced levels of core pathological markers (Aβ1–42, Tau, p-Tau (Ser404), GSK-3β), decreased expression of pro-inflammatory mediators including IL-33, elevated levels of neurotrophic factors (BDNF and MAP2), and attenuated abnormal activation of astrocytes and microglia. The 16S rRNA analysis confirmed that CFE ameliorated gut microbial dysbiosis. Notably, CFE significantly increased the relative abundance of Muribaculaceae and Lachnospiraceae, while significantly decreased Staphylococcus and Helicobacter. Metabolomics revealed enhanced levels of α-linolenic acid (ALA), serotonin (5-HT) and acetic acid, which correlated positively with Muribaculaceae and Lachnospiraceae. Phytochemical analysis identified luteolin and kaempferol as the predominant flavonoids in CFE. In BV2 cells, CFE, luteolin and kaempferol shifted microglial polarization from the M1 phenotype toward the M2 phenotype. Conclusions: CFE alleviated HNF-induced cognitive decline by regulating microbiota-gut-brain axis and microglial M1/M2 polarization.