Valorization of Agri-Food Waste from Pistachio Hard Shells: Extraction of Polyphenols as Natural Antioxidants

Abstract

The agricultural processing industry usually generates a remarkable amount of by-products rich in bioactive compounds, which can be exploited for agri-food or nutraceutical applications. Pistachio’s hard shell is one of the major by-products from pistachio industrial processing. The aim of this work was the evaluation of pistachio shells as a potential source of natural antioxidants. We evaluated different extraction procedures by measuring total phenolic content, total flavonoid content and antioxidative activity (DPPH•, TEAC and ORAC). The microwave-assisted ethanol extract turned out to be the most promising and was fractionated by XAD-16 column chromatography, affording six fractions analyzed through HPLC/ESI-MS/MS and 1H-NMR to identify the main antioxidative constituents. Fractions Fr4–Fr6 demonstrated the highest antioxidant activity. Gallic acid and a monogalloylglusose isomer are the main phenolic constituents of Fr4. Both simple and complex phenolics, such as flavonoids and hydrolysable tannins, were identified in fractions Fr5 and Fr6; pentagalloylglucose and kaempferol, well-known for their antioxidant activity, are the most abundant constituents. The results highlighted that the proposed methodology can be an effective way to recover bioactive phenolic compounds from pistachio hard shell, making this by-product a promising source of compounds with potential applications in food and healthcare sectors.

Immunometabolism Modulation by Extracts from Pistachio Stalks Formulated in Phospholipid Vesicles

“…In agreement with previous findings, the most abundant metabolites identified in the extracts were α-amino acids (tryptophan, tyrosine), hydroxycinnamic acids (vanillic acid, p -coumaric acid, sinapinic acid, caffeic acid, cinnamic acid and ferulic acid), saturated fatty acid (myristic acid), flavone (luteolin), flavan-3-ol (catechin), terpene (α-pinene), vitamin (ascorbic acid), and flavanone (naringenin) [ 22 , 23 , 28 , 29 , 30 , 31 , 32 ]. Of note, α-pinene was the only compound detected in the essential oil and not in the hydrolate ( Figure 1 and Figure 2 ).…”

Green3: A green extraction of green additives for green plastics

“…The TPC of extracts was evaluated by the Folin–Ciocalteu assay, as already reported [ 3 ]. Briefly, samples were solubilized at a concentration of 10 mg/mL and diluted to 0.5 mg/mL.…”

“…Recently, other shells as by-products from the agrifood industry, namely almond and pistachio hard shells [ 3 , 4 ], were extracted with alcoholic solutions to yield antioxidant constituents, including tannins, flavonoid glycosides, and phenolic acids derivatives. In a similar work, carried out on hazelnut skin by-product, several natural deep eutectic solvents (NADES) were investigated to optimize the extraction of bioactive compounds, highlighting the use of bio-renewable DES to recover natural antioxidants from hazelnut by-products [ 5 ].…”

Interaction between Dietary Fibre and Bioactive Compounds in Plant By-Products: Impact on Bioaccessibility and Bioavailability

“…Phenolic acids, including ferulic acid, sinapic acid, and p -coumaric acid, among others, are mainly found in cereal fibres [ 111 ]. On the other hand, flavonoids have been described as the major (poly)phenols in citrus fibre [ 112 ], and hydrolysable tannins have been found mainly in pomegranate and nut fibres [ 113 , 114 ].…”