Antioxidant Properties of Agri-Food Byproducts and Specific Boosting Effects of Hydrolytic Treatments

Abstract

Largely produced agri-food byproducts represent a sustainable and easily available source of phenolic compounds, such as lignins and tannins, endowed with potent antioxidant properties. We report herein the characterization of the antioxidant properties of nine plant-derived byproducts. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays indicated the superior activity of pomegranate peels and seeds, grape pomace and pecan nut shell. An increase in the antioxidant potency was observed for most of the waste materials following a hydrolytic treatment, with the exception of the condensed tannin-rich pecan nut shell and grape pomace. UV-Vis and HPLC investigation of the soluble fractions coupled with the results from IR analysis and chemical degradation approaches on the whole materials allowed to conclude that the improvement of the antioxidant properties was due not only to removal of non-active components (mainly carbohydrates), but also to structural modifications of the phenolic compounds. Parallel experiments run on natural and bioinspired model phenolic polymers suggested that these structural modifications positively impacted on the antioxidant properties of lignins and hydrolyzable tannins, whereas significant degradation of condensed tannin moieties occurred, likely responsible for the lowering of the reducing power observed for grape pomace and pecan nut shell. These results open new perspectives toward the exploitation and manipulation of agri-food byproducts for application as antioxidant additives in functional materials.

A tunable deep eutectic solvent-based processing for valorization of chestnut wood fiber as a source of ellagic acid and lignin

“…44% and 51% yield for the ChCl:TA2 and ChCl:LA2 sample, respectively. As expected, based on the high solubility of EA in DMSO, HPLC analysis of the supernatants indicated the complete solubilization of this compound, whereas no detectable amount of EA was present in the precipitates, as demonstrated by 1 H NMR analysis of these latter after immediate dissolution in DMSO-d 6 (data not shown).…”

“…A.10 the ATR-FTIR spectra of the ChCl:TA2 sample before (black trace) and after (red trace) washing with DMSO are shown, together with those of a commercial EA sample (blue trace). As expected, no traces of this latter were present in the DMSO-washed sample, which was instead characterized by two sharp peaks in the 2950-2850 cm − 1 region (evident also in the spectrum of the unwashed sample), typically associated to the C− H stretching vibration of lignins [1,8]. On the other hand, the spectrum of the starting ChCl:TA2 sample was almost superimposable to that of EA, particularly in the region between 1700 and 500 cm -1 (Fig.…”

“…Agri-food industry is responsible for the generation of up to 140 billion tons per year of organic wastes/by-products [1][2][3][4] which can be considered as a largely available, low-cost source of value-added compounds such as polyphenols, including mainly flavonoids and phenolic acids [5][6][7][8][9][10][11]. These latter are well-known for their health beneficial effects [6,12], ascribed in part to their efficient antioxidant properties [13] that have also recently prompted their use as additives for implementation of functional materials.…”

Analysis, Development, and Scaling-Up of Poly(lactic acid) (PLA) Biocomposites with Hazelnuts Shell Powder (HSP)

“…HSPs consist of lignin (40–50% by weight), cellulose (25–28%), and hemicellulose (22–30%), but they also contain a fraction of polyphenols (flavonoids and tannins), which can be recovered by hydroalcoholic extraction [ 10 , 11 , 12 ]. The shell extracts can be used as natural antioxidants in polymeric matrices as they can act as thermal and photo oxidative stabilizers for different types of polymers, including biopolymers like poly(lactic) acid (PLA) [ 13 , 14 ]. Moreover, the HSP addition enables light biocomposites to be obtained that, in some cases, possess improved mechanical and thermal properties and have enhanced biodegradability, when compared to the pure matrices [ 15 , 16 , 17 , 18 , 19 ].…”

Hydrolyzable vs. Condensed Wood Tannins for Bio-based Antioxidant Coatings: Superior Properties of Quebracho Tannins

“…These are traditionally classified as hydrolyzable or condensed (non-hydrolyzable) tannins. Chestnut tannins are composed mainly of hydrolyzable ellagitannins such as castalagin and its isomer vescalagin [ 6 , 7 ], whereas quebracho tannins comprise mainly condensed tannins of which linear profisetinidins represent the major constituents [ 8 , 9 , 10 ] ( Figure 1 ).…”