Comparative Flavan-3-ol Profile and Antioxidant Capacity of Roasted Peanut, Hazelnut, and Almond Skins

Abstract

In the present study, the flavan-3-ol composition and antioxidant capacity of roasted skins obtained from the industrial processing of three commonly consumed tree nuts (i.e., peanuts, hazelnuts, and almonds), as well as fractions containing low and high molecular weight (LMW and HMW) flavan-3-ols, were studied with the aim of assessing their potential as a source of flavonoids. Roasted peanut and hazelnut skins presented similar total phenolic contents, much higher than that of almond skins, but their flavan-3-ol profiles, as determined by LC-ESI-MS and MALDI-TOF MS, differed considerably. Peanut skins were low in monomeric flavan-3-ols (19%) in comparison to hazelnut (90%) and almond (89%) skins. On the other hand, polymeric flavan-3-ols in peanut and almond skins occurred as both A- and B-type proanthocyanidins, but in peanuts the A forms (up to DP12) were predominant, whereas in almonds the B forms (up to DP8) were more abundant. In contrast, hazelnuts were mainly constituted by B-type proanthocyanidins (up to DP9). The antioxidant capacity as determined by various methods (i.e., total antioxidant capacity, ORAC, DPPH test, and reducing power) was higher for whole extracts from roasted hazelnut and peanut skins than for almond skins; however, the antioxidant capacities of the HMW fraction of the three types of nut skins were equivalent despite their different compositions and DPs. Nevertheless, the large variation in flavan-3-ol concentration, structural composition, type of interflavan linkage, and DP found among the three types of nut skins suggests large difference in their expected in vivo biological activities.

Antioxidant and Anti-Inflammatory Effects of Peanut Skin Extracts

“…The profiles observed in this study are similar to those previously reported [22,28]. Previous studies have confirmed that the procyanidin oligomers in peanut skins contain both B-linkages as well as the less common A-type linkages [28][29][30]. Overall, the profiles produced by the two solvent systems were similar; however, it is visually evident that acetone/water was a more effective extraction solvent for procyandins than ethanol/water as indicated by the larger peak areas.…”

“…Peanut skins have been reported to contain a variety of bioactive compounds with phenolic moieties, including catechins, A-type and B-type procyanidin dimers, trimers, and tetramers [22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Extraction of these compounds has been studied with various extraction solvents.…”

Tree nut phytochemicals: composition, antioxidant capacity, bioactivity, impact factors. A systematic review of almonds, Brazils, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts

“…Polyphenols have been further characterised in hazelnut skins. Monagas et al (15) reported the catechin content and Del Rio et al (38) reported monomeric and oligomeric flavan-3-ols, flavonols, dihydrochalcones and phenolic acids in hazelnut skins. Although these studies did not report polyphenol content in terms of whole hazelnuts, monomeric and oligomeric (5) 2052 (28,80,86,92) 2713·49 (10 -12,18,28) 493·90 (1) 233·52 (70,169,170,175) ND Pine nuts 206 26 (5) ND 0·03 (11,12) 1 (11,13,18,43) § 190·75 (70,169,170,175,189,190) ND Pistachios 703 22 832 (5,50,87) 1·27 (191) 136·45 (10 -12,18,40,42,43,191) 252·71 (1) 189·43 (70,88,169 -171,175,192) 803·22 (40,43,48,49) Walnuts 1602 21 (5) 39·11 (44,51,60,193,194) 0·54 (11,…”

Yağlı Tohum Kabuklarının Biyoaktif Bileşen Potansiyeli ve Gıdalarda Kullanımı

“…Contini ve ark. [23] [24]. Taş ve Gökmen [25] toplam antioksidan miktarının fındık iç kabuğunda fındığa göre 100 kat, α-tokoferolün iki kat daha fazla olduğunu fındık içi kabuğunun çekirdekle karşılaştırıldığında biyoaktif bileşenlerce zengin bir kaynak olabileceğini belirtmişlerdir.…”