Diversity of Chemical Structures and Biosynthesis of Polyphenols in Nut-Bearing Species

Abstract

Nuts, such as peanut, almond, and chestnut, are valuable food crops for humans being important sources of fatty acids, vitamins, minerals, and polyphenols. Polyphenols, such as flavonoids, stilbenoids, and hydroxycinnamates, represent a group of plant-specialized (secondary) metabolites which are characterized as health-beneficial antioxidants within the human diet as well as physiological stress protectants within the plant. In food chemistry research, a multitude of polyphenols contained in culinary nuts have been studied leading to the identification of their chemical properties and bioactivities. Although functional elucidation of the biosynthetic genes of polyphenols in nut species is crucially important for crop improvement in the creation of higher-quality nuts and stress-tolerant cultivars, the chemical diversity of nut polyphenols and the key biosynthetic genes responsible for their production are still largely uncharacterized. However, current technical advances in whole-genome sequencing have facilitated that nut plant species became model plants for omics-based approaches. Here, we review the chemical diversity of seed polyphenols in majorly consumed nut species coupled to insights into their biological activities. Furthermore, we present an example of the annotation of key genes involved in polyphenolic biosynthesis in peanut using comparative genomics as a case study outlining how we are approaching omics-based approaches of the nut plant species.

Polyphenols and Maillard Reaction Products in Dried Prunus spinosa Fruits: Quality Aspects and Contribution to Anti-Inflammatory and Antioxidant Activity in Human Immune Cells Ex Vivo

“…Moreover, partial isomerisation of pseudodepsides could also take place; an example is the case of p -coumaroylshikimic acids (36, 39), among which one was present in both materials (36) but second only in dried sloes (39). Furthermore, three other drying-related processes, such as the oxidative coupling of caffeoylquinic acids [ 28 ], depolymerisation of condensed proanthocyanidins [ 21 ], and recovery of polyphenols from lignified stone tissue [ 29 ] were probably responsible for the presence of caffeoylquinic acid dehydrodimer (29), (epi)catechin derivative (13), and aromadendrin hexoside (37) in dried fruits, respectively.…”

Adsorption of Polyphenols from Almond Blanching Water by Macroporous Resin

“…This leads to an increase in the concentration of catechin, epicatechin, and their oligomers, as well as kaempferol and isorhamnetin. In their study, Aneklaphakij et al [ 32 ] confirmed the presence of chalcones in almond kernel skins. In addition, Khan et al [ 33 ] demonstrated that naringenin and hesperetin chalcones spontaneously undergo cyclization back to the parent flavanones under neutral conditions.…”

Phytochemical Profile and Antioxidant, Antiproliferative, and Antimicrobial Properties of Rubus idaeus Seed Powder

“…The remaining glycosylated polyphenols were conjugated to galactose (#3, #11, and #20), glucose (#2, #4, #14, #15, and #18), arabinose (#7), diglucoside (#10, #33, #36, and #37), rutinoside (#5, #6, #26, and #34), xylose (#9), sambubiose (#16), or glucuronic acid (#35) moiety. Scientific studies evaluating the potential bioavailability of polyphenols have frequently indicated that aglycones are poorly permeable to biological membranes [ 31 , 35 , 36 , 37 ]. Consequently, potential local activity of these phenols after ingestion of foods enriched with these phytochemicals can be presumed [ 31 , 36 ].…”