Walnut septa, traditionally discarded as waste in walnut processing because they primarily serve a structural function in the walnut fruit, have recently gained attention for their potential abundance of phenolic compounds, suggesting their overlooked value. This study aimed to optimise extraction parameters to maximise the extraction yield of bioactive compounds and explore regional variations in antioxidant activity and chemical composition of Juglans regia L. septa. The experimental variables included extraction methods (maceration, dynamic maceration, ultrasound processing, and reflux extraction), temperature, solvent type (methanol, acetone, and ethanol), and the percentage of water in the solvent. The optimal conditions were determined based on the total phenolic content—reflux extraction using 60% ethanol as a solvent for a duration of 60 min. Samples from 12 different regions in Lithuania, Armenia, and Ukraine were analysed for their phenolic and proanthocyanidin content and antioxidant activity using the CUPRAC method. The total phenolic content ranged from 131.55 to 530.92 mg of gallic acid equivalents per g of dry weight of plant material (mg GAE/g dw), while the proanthocyanidin content varied from 1.14 to 7.65 mg of (–)-epicatechin equivalents per g dry weight of plant material (mg EE/g dw). Among all the regions studied, the Šiauliai sample demonstrated the highest concentrations of phenolic compounds, proanthocyanidins, and antioxidant activity, with statistically significant differences compared to the other samples (p < 0.05). These findings demonstrate that walnut septa are a valuable source of phenolic compounds and antioxidants, with significant potential for developing natural nutraceuticals and antioxidant products.

Walnut septum (WS), a major by-product of walnut processing, represents a promising source of bioactive compounds with potential antioxidant and antimicrobial properties. This study aimed to characterise the phytochemical composition of WS extracts from different habitat origins and evaluate their antimicrobial activity. Total amino acids were profiled by gas chromatography–mass spectrometry, while phenolic compounds were analysed using high-performance liquid chromatography. Both methods were evaluated according to ICH Q2 (R2) guidelines for analytical procedure validation. The results showed a complex composition of amino acids and polyphenols, including ellagic acid and quercitrin. However, it was clear that habitat variations in WS samples had a significant impact on the quantities and composition of phenolic compounds and total amino acids in WS extracts. Antimicrobial activity was assessed against Gram-positive and Gram-negative bacterial strains. Variations in antimicrobial efficacy were associated with differences in phenolic composition and content due to habitat differences in WS sample origins. Collectively, this study highlights the WS as a valuable agro-industrial by-product with potential applications as a natural source of antimicrobial compounds in food and pharmaceutical systems.

Background/Objectives: Juglans regia L. septa are a rich source of phenolic compounds with potential skin-related biological activity. This study evaluated the cytoprotective activity of a lyophilised J. regia septum extract and developed extract-containing polymeric gels suitable for topical application and semi-solid extrusion (SSE) 3D printing. Methods: The extract was characterised by high-performance liquid chromatography with photodiode array detection (HPLC-PDA) and evaluated in H₂O₂-exposed human fibroblasts. Poly(vinyl alcohol) (PVA)-, sodium carboxymethyl cellulose (CMC)-, and hydroxyethyl cellulose (HEC)-based gels were prepared, and the selected formulation was processed into films by solvent casting and SSE 3D printing. The films were evaluated for thickness, moisture content, mechanical properties, and probe–film adhesiveness. Results: Ellagic acid was the predominant quantified phenolic compound (36.453 µg/mL). The free extract protected fibroblasts against H₂O₂-induced oxidative damage, with the greatest preservation of viable cells at 75 and 100 µg/mL. Increasing extract loading increased total quantified phenolic content in the gels from 10.95 to 27.98 µg/mL. The selected formulation was successfully processed into multilayer films. 3D-printed films showed numerically lower burst strength and breaking force per unit width than solvent-cast films, although pairwise differences were not significant. Hydration increased probe–film adhesiveness, while film moisture content decreased during 3 months of storage. Conclusions: These findings support the feasibility of incorporating cytoprotective J. regia extract into printable polymeric gels for topical film development.