Phytochemical profiling and biological evaluation of hazelnut shell extract reveals neuroprotective potential in human microglial cells.

BACKGROUND: Neurotoxicity and chronic neuroinflammation are complex pathological processes involving the overactivation of microglia, which can lead to functional impairments in the central nervous system. This study aimed to characterize the phytochemical profile of the aqueous extract of hazelnut shell (Corylus avellana) an agricultural by-product, and to evaluate its neuroprotective potential comprehensively in the human microglial cell line (HMC-3). METHODS AND RESULTS: Liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis revealed that the extract contained several phenolic compounds, with quinic acid (2602.88 µg/g), chlorogenic acid (1583.80 µg/g), and gallic acid (983.50 µg/g) being the predominant constituents. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT) and Lactate dehydrogenase (LDH) release assays conducted on HMC-3 cells revealed that concentrations of up to 62.5 µg/mL-maintained cell viability above 70%, effectively preserving metabolic activity and membrane integrity. Quantitative analysis of inflammatory markers revealed that the extract significantly suppressed the levels of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α (p < 0.05). Regarding oxidative balance, total oxidant status (TOS) remained stable while total antioxidant capacity (TAC) increased significantly, particularly at 400 µg/mL (0.914 ± 0.146 mmol Trolox Eq/L). Furthermore, antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa was confirmed at various concentrations via disk diffusion and optical density methods. CONCLUSION: The hazelnut shell extract is a promising natural biocomponent for regulating neuroinflammation and developing neuroprotective strategies due to the anti-inflammatory and antioxidant effects of its bioactive compounds.