072 | A standardized onion peel-derived bioactive ingredient attenuates palmitate-induced steatosis and oxidative stress in HepG2 cells

Ilaria Di Gregorio^1|2, Vincenzo Migliaccio², Maria D’Elia^1|3|4, Rita Celano^1|3, Anna Lisa Piccinelli^1|3, Luca Rastrelli^1|3, Lillà Lionetti^2|3 | ¹Dept Pharmacy, University of Salerno, Salerno, Italy; ²Dept Chemistry and Biology “A Zambelli”, University of Salerno, Italy; ³National Biodiversity Future Center NBFC, Palermo, Italy; ⁴Dept Earth and Marine Sciences, University of Palermo, Italy.

Onion peel represents a valuable food by-product rich in bioactive phenolic compounds. Building on previous phytochemical investigations, an onion peel extract obtained from the Rossa di Tropea variety was further developed as a standardized bioactive ingredient (OPI-T). The present study aimed to evaluate the antioxidant and antisteatotic effects of OPI-T using an in vitro tumour cell model (HepG2). An onion peel extract derived from the Ramata di Montoro variety was included as a natural negative reference to account for varietal variability. It is well known that hepatic steatosis is associated with cellular and oxidative stress. Furthermore, oxidative stress is related to mitochondrial dysfunction which is closely related to mechanisms of mitochondrial dynamics in terms of fusion and fission. Mitochondrial fusion is useful for improving mitochondrial function in response to cellular stress conditions, while mitochondrial fission is associated with mitochondrial dysfunction. In the present work HepG2 were treated with palmitate (500 µM) to induce hepatic steatosis and oxidative stress. To evaluate the possible protective effect of the extract, treatments of HepG2 cells were carried out simultaneously with palmitate and OPI-T at concentrations of 25 or 50 µg/mL. Hepatic steatosis was evaluated using the oil red O and Bodipy methods; oxidative stress was determined by the DCF assay. Mitochondrial dynamics protein content (namely, Mitofusin, MFN2, as a fusion marker, and Dynamin-related fission marker, DRP1, as a fission marker) and autophagy flux markers (Sequestosome 1, SQSTM1/P62 and microtubule-associated protein 1 light chain 3, LC3 II/I) were determined by western blot. The results showed that OPI-T significantly attenuated palmitate-induced lipid accumulation and reduced intracellular ROS production, while modulating mitochondrial dynamics toward a reduced fission phenotype and improving autophagy flux. In contrast, the Montoro extract showed weaker effects on lipid accumulation and ROS production. Overall, these findings support the functional validation of a standardized onion peel–derived ingredient, highlighting its potential application as a bioactive component for functional food or nutraceutical development targeting hepatic steatosis and oxidative stress. Further studies are needed to elucidate the molecular mechanisms underlying these effects and to identify the specific compounds responsible for the observed biological activities.
Funding: This project was funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4—Call for tender No. 3138 of 16 December 2021, rectified by Decree n.3175 of 18 December 2021 of Italian Ministry of University and Research funded by the Europe-an Union—NextGenerationEU; Award Number: Project code CN_00000033, Concession Decree No. 1034 of 17 June 2022 adopted by the Italian Ministry of University and Research, CUP: D43C22001260001, Project title “National Biodiversity Future Center—NBFC”.