Antioxidant Activity of a Sicilian Almond Skin Extract Using In Vitro and In Vivo Models

Abstract

Almond skins are known for their antioxidative and anti-inflammatory properties, which are mainly due to the presence of polyphenols. The aim of the present study was to evaluate the antioxidant and anti-inflammatory effects of almond skin extract (ASE) obtained from the Sicilian cultivar “Fascionello” and to evaluate the possible mechanisms of action using an in vitro model of human monocytic U937 cells as well as an in vivo model of carrageenan (CAR)-induced paw edema. The in vitro studies demonstrated that pretreatment with ASE inhibited the formation of ROS and apoptosis. The in vivo studies showed that ASE restored the CAR-induced tissue changes; restored the activity of endogenous antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione; and decreased neutrophil infiltration, lipid peroxidation, and the release of proinflammatory mediators. The anti-inflammatory and antioxidant effects of ASE could be associated with the inhibition of the pro-inflammatory nuclear NF-κB and the activation of the nuclear factor-erythroid 2-related factor 2 (Nrf2) antioxidant pathways. In conclusion, almond skin could reduce the levels of inflammation and oxidative stress and could be beneficial in the treatment of several disorders.

Specific Antimicrobial Activities Revealed by Comparative Evaluation of Selected Gemmotherapy Extracts

“…The almond (Prunus amygdalus L.) belongs to the Rosaceae family, and it is cultivated in east Mediterranean countries, Australia and Africa [25]. The skin of the nut has antiinflammatory and antioxidant activities due to the presence of nutrients, such as lipids, fatty acids, proteins, amino acids, vitamins, carbohydrates and minerals [26]. The sphingolipids isolated from nuts are capable of inhibiting the development of colon cancer and also decreasing the proportion of adenocarcinomas in mice [25].…”

A Green Bioactive By-Product Almond Skin Functional Extract for Developing Nutraceutical Formulations with Potential Antimetabolic Activity

“…A rapid HPLC-UV method was applied to investigate the DSA lio polyphenolic profile [25]. Nine unknown compounds within acid phenolic, flavanol, and flavonol classes were observed: gallic acid (1), procyanidin B3 (2), procyanidin B1 (3), catechin (4), epicatechin (5), procyanidin C1 (6), kaempferol 3-O-rutinoside (7), isorhamnetin-3-Orutinoside (8), and quercetin (9) (Figure S1). The compounds were identified by comparing their retention time (Figure S1) and mass spectral data (Table 1 and Figure S2) with those of pure standards.…”

“…The following supporting information can be downloaded: https://www. mdpi.com/article/10.3390/molecules28237913/s1, Figure S1: HPLC-UV profile of DSA: Gallic acid (1) procyanidin B3 (2), procyanidin B1 (3), catechin (4), epicatechin (5), procyanidin C1 (6), kaempferol 3-O-rutinoside (7), isorhamnetin-3-O-rutinoside (8), and quercetin (9); Figure S2: MS/MS spectra of phenolic compounds in DSA; Figure S3: Cell vitality on A375 (A), A549 (B), and HaCaT (C) cells was calculated as: % vitality = [100 × (OD treated/OD control)]. Results were analyzed using the nonparametric Mann-Whitney U test; Table S1: %RH ± SD (n = 3) of processed (40 • C ± 2 • C) and unprocessed skin almond samples.…”

“…It showed to be active on TNF-α-inhibition, one of the leading mediators of intestinal inflammation [7]. These effects are mainly due to the polyphenol's antioxidant and radical scavenging properties [8][9][10]. Indeed, reactive oxygen (ROS) and nitrogen (RNS) species are factors strictly related to inflammation.…”