Contribution of bioactive compounds from walnut and almond by-products to the modulation of oxidative stress and cell survival in Caco-2 cells.

Nut flours, byproducts of the oil industry, are an edible source for functional foods from a safe, gluten-free, sustainable, and raw material. In particular, walnut (WF) and almond (AF) flours are enriched in polyphenols and other bioactive substances that could present antioxidant and antiproliferative properties. In the present study, WF and AF phenolic profile were determined and their impact on antioxidant and cell viability has been examined through a cellular model.

Partially defatted flours by screw press were defatted, and polyphenols were extracted [MetOH 80 :H2O 20]. The total amount of polyphenols (PT) was evaluated by FOLIN-CT and the phenolic profile by UPLC-QqQ mass spectrometry. Intracellular oxidation (DCFH-DA) and cell death (Trypan Blue) were assessed as mean intensity by flow cytometry in Caco-2 cells with increasing PT doses for 24 h (WF: 17-250 µg/mL of PT; AF: 1.7-25.0 µg/mL of PT). H₂O₂ (1.5 mM, 1 h) was used as an oxidative stress model after treatments. Statistics: MLGM, (n=3). DCG post-test.

The WF major compounds found were: Quercetin pentoside isomer> Glansreginin A> Catechin>Gallic acid. Regarding AF, the major compounds were: Quinic acid> Hesperidin> Isorh-3-O-rutinoside> Epicatechin. WF exhibited a reduction in oxidation (50%), while did not compromise cell viability except at 250 µg/mL. The AF showed a 20% a decrease in oxidation and a dose-dependent increase in cell death (90%). Also, WF showed a notable attenuation of H₂O₂-induced oxidation (200%) and cell death (100%). The AF provoked a dose-dependent reduction of oxidation (200%). AF doses increased the toxicity of the oxidative model.

In conclusion, WF showed a strong preventive antioxidation response, meanwhile AF notably induce antiproliferative action, suggesting a chemoprotective potential linked to their specific phenolic profile. This study highlights the importance of analyzing the phenolic composition in correlation with the bioactivity assessment of different nut flours from a nutritional therapy perspective.