Investigation of the antioxidant capacity and phenolic constituents of U.S. pecans

Targeted metabolomics reveals key phenolic changes in pecan nut quality deterioration under different storage conditions

Pecan nuts are highly enriched in phenolic compounds, which contribute to the health benefits of pecans. Phenolic compounds represent the main oxidation reaction substrates, thus leading to quality deterioration, namely pellicle browning or a decrease in beneficial effects during pecan storage. Hence, four different storage conditions were performed for 180 d to simulate real production situations. Targeted metabolomics was chosen to identify the specific phenolic compounds involved in quality deterioration under different storage conditions in 0, 90, and 180 d samples. A total of 118 phenolic compounds were detected, nine of which were identified for the first time in pecan. The total phenolic content (TPC) and antioxidant capacities initially demonstrated high scores, after which they tended to decrease during the storage process. The significantly modified phenolic compounds during storage were selected as the metabolite markers of pecan quality deterioration, including catechin, procyanidin (PA) trimer, PA tetramer, trigalloyl hexahydroxydiphenoyl (HHDP) glucose, and tetragalloyl hexoside. Fresh pecan kernels resulted in more pronounced changes in hydrolysable tannins (HTs), whereas dry kernels resulted in the most accentuated changes in condensed tannins (CTs). To the best of our knowledge, this is the first attempt to study individual phenolic changes during storage of pecan in such massive amounts. The results can offer a valuable theoretical basis for future control of pecan quality deterioration through phenolics during storage.

The Impact of Ellagitannins and Their Metabolites through Gut Microbiome on the Gut Health and Brain Wellness within the Gut-Brain Axis

Ellagitannins (ETs) are a large group of bioactive compounds found in plant-source foods, such as pomegranates, berries, and nuts. The consumption of ETs has often been associated with positive effects on many pathologies, including cardiovascular diseases, neurodegenerative syndromes, and cancer. Although multiple biological activities (antioxidant, anti-inflammatory, chemopreventive) have been discussed for ETs, their limited bioavailability prevents reaching significant concentrations in systemic circulation. Instead, urolithins, ET gut microbiota-derived metabolites, are better absorbed and could be the bioactive molecules responsible for the antioxidant and anti-inflammatory activities or anti-tumor cell progression. In this review, we examined the dietary sources, metabolism, and bioavailability of ETs, and analyzed the last recent findings on ETs, ellagic acid, and urolithins, their intestinal and brain activities, the potential mechanisms of action, and the connection between the ET microbiota metabolism and the consequences detected on the gut-brain axis. The current in vitro, in vivo, and clinical studies indicate that ET-rich foods, individual gut microbiomes, or urolithin types could modulate signaling pathways and promote beneficial health effects. A better understanding of the role of these metabolites in disease pathogenesis may assist in the prevention or treatment of pathologies targeting the gut-brain axis.

Chemical Composition and Antioxidant Properties of Pecan Shell Water Extracts

This study examined the chemical composition and antioxidant properties of the extracts obtained from two byproduct streams generated at a commercial pecan nut shelling operation. Byproduct stream F contained more pecan nut meat pieces and packing material than stream S, consisting of mainly hard outer shell pieces. Samples from Native variety nuts were processed using subcritical, sonication aided and microwave heating, using water as a solvent. Ferric reducing capacity (FRAP), Total Phenolic Content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ABTS [2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)] assays were used to determine antioxidant properties of the extracts. The experimental results clearly demonstrated that the chemical composition of the industrial byproducts was significantly different from the hand-separated shells. All the water extracts exhibited significant DPPH, ABTS and FRAP activity. The highest antioxidant capacity was obtained with the extracts obtained via subcritical water at 80 °C. This is the first report published in the literature on the antioxidant properties of water extracts obtained from industrial byproducts from a pecan nut shelling operation processing Native variety. New data generated in this study expand our knowledge of the properties of industrial nut shelling industry byproducts and help to evaluate the potential use of the shell extracts as antioxidants in various applications.

Proanthocyanidins and Where to Find Them: A Meta-Analytic Approach to Investigate Their Chemistry, Biosynthesis, Distribution, and Effect on Human Health

Proanthocyanidins (PACs) are a class of polyphenolic compounds that are attracting considerable interest in the nutraceutical field due to their potential health benefits. However, knowledge about the chemistry, biosynthesis, and distribution of PACs is limited. This review summarizes the main chemical characteristics and biosynthetic pathways and the main analytical methods aimed at their identification and quantification in raw plant matrices. Furthermore, meta-analytic approaches were used to identify the main plant sources in which PACs were contained and to investigate their potential effect on human health. In particular, a cluster analysis identified PACs in 35 different plant families and 60 different plant parts normally consumed in the human diet. On the other hand, a literature search, coupled with forest plot analyses, highlighted how PACs can be actively involved in both local and systemic effects. Finally, the potential mechanisms of action through which PACs may impact human health were investigated, focusing on their systemic hypoglycemic and lipid-lowering effects and their local anti-inflammatory actions on the intestinal epithelium. Overall, this review may be considered a complete report in which chemical, biosynthetic, ecological, and pharmacological aspects of PACs are discussed.

Examining the Performance of Two Extraction Solvent Systems on Phenolic Constituents from U.S. Southeastern Blackberries

Two common extraction solvent systems, namely acidified aqueous methanol and acidified aqueous acetone, were used to extract blackberry phenolics, and the antioxidant properties of the recovered extracts were compared. The crude extracts were fractionated into low- and high-molecular-weight phenolics by Sephadex LH-20 column chromatography. The hydrophilic-oxygen radical absorbance capacity (H-ORAC_FL), ferric reducing antioxidant power (FRAP), and the cellular antioxidant activity (CAA) assays were employed as indices to assess antioxidant capacity of the extracts and their respective fractions. The methanolic solvent system displayed a greater efficiency at extracting anthocyanin and flavonol constituents from the blackberries, while the acetonic solvent system was better at extracting flavan-3-ols and tannins. Anthocyanins were the dominant phenolic class found in the blackberries with 138.7 ± 9.8 mg C3G eq./100 g f.w. when using methanol as the extractant and 114.6 ± 3.4 mg C3G eq./100 g f.w. when using acetone. In terms of overall antioxidant capacity of blackberry phenolics, the acetonic solvent system was superior. Though present only as a small percentage of the total phenolics in each crude extract, the flavan-3-ols (42.37 ± 2.44 and 51.44 ± 3.15 mg/100 g f.w. in MLF and ALF, respectively) and ellagitannins (5.15 ± 0.78 and 9.31 ± 0.63 mg/100 g f.w. in MHF and AHF, respectively) appear to account for the differences in the observed antioxidant activity between the two solvent systems.

Tree Nuts and Peanuts as a Source of Natural Antioxidants in our Daily Diet

Tree nuts and peanuts are healthy foods with a proven track record of helping to reduce the incidence of chronic diseases, most notably cardiovascular disease. At the point of consumption, all nuts contain low moisture and ≥ 50% lipid contents, but this is where similarities end. The levels of key nutrients and bioactives including vitamin C, vitamin E, L-arginine, minerals (such as selenium and zinc), and phenolics can differ markedly. Distinctions in the types and quantities of phenolic constituents for tree nut species, as well as the impact of digestion, will affect the nuts' antioxidant potential in vivo. This work provides some insight into the different types of phenolics found in tree nuts and peanuts, the antioxidant potential of their phenolic extracts using in vitro chemical assays, the effect of thermal processing on the stability of the nuts' endogenous phenolics, and the impact on biomarkers of human health arising from randomized clinical trials. Key biomarkers include measures in the reduction of LDL oxidation as well as increases in the levels of vitamin E and selected phenolic compounds in blood plasma postprandially from those of baseline.

Metabolic profiling revealed the organ-specific distribution differences of tannins and flavonols in pecan

Carya illinoinensis is rich in phenolic metabolites such as tannins and flavonols, but both the composition and the distribution of these nutritional constituents in most pecan organs were still unclear. In this experiment, a comprehensive qualification and quantification of phenolic metabolites in eight organs of pecan were conducted for the first time. Ninety-seven phenolic metabolites were identified, in which twelve were identified for the first time in pecan, including a series of ellagitannins with high molecular weight. Hydrolysable tannin was the dominant kind of phenolic metabolites in pecan. The metabolic profiles of tannins in pecan were extended. Thirty-three phenolic metabolites were quantified, among them the highest content was ellagic acid pentose in testa. From this experiment, we can see that the distribution of phenolic metabolites in pecan was organ-specific, tannins tend to accumulate in pecan testa with both diverse structures and high contents, while flavonols tend to accumulate in organs such as branch, bark, or leaf. Among all organs, testa contained the highest content of phenolics, which might play important roles in protecting pecan kernel from diseases and insects. A massive phenolic metabolites' matrix in different pecan organs was built in this experiment, which should be useful for related researches in the future and help provide a theoretical basis for using these organs as functional foods.

Advances and Prospects of Phenolic Acids Production, Biorefinery and Analysis

Biotechnological production of phenolic acids is attracting increased interest due to their superior antioxidant activity, as well as other antimicrobial, dietary, and health benefits. As secondary metabolites, primarily found in plants and fungi, they are effective free radical scavengers due to the phenolic group available in their structure. Therefore, phenolic acids are widely utilised by pharmaceutical, food, cosmetic, and chemical industries. A demand for phenolic acids is mostly satisfied by utilising chemically synthesised compounds, with only a low quantity obtained from natural sources. As an alternative to chemical synthesis, environmentally friendly bio-based technologies are necessary for development in large-scale production. One of the most promising sustainable technologies is the utilisation of microbial cell factories for biosynthesis of phenolic acids. In this paper, we perform a systematic comparison of the best known natural sources of phenolic acids. The advances and prospects in the development of microbial cell factories for biosynthesis of these bioactive compounds are discussed in more detail. A special consideration is given to the modern production methods and analytics of phenolic acids.

Characterization of Free and Bound Phenolic Acids and Flavonoid Aglycones in Rosa rugosa Thunb. Leaves and Achenes Using LC-ESI-MS/MS-MRM Methods

Fast and reliable determination of polyphenols is a quite common goal during investigation of new plant materials and herbal products, their standardization, quality control, or chemo-taxonomical studies. The aim of this study was to develop and validate methods based on the application of reversed phase liquid chromatography/electrospray ionization triple quadrupole mass spectrometry (LC-ESI-MS/MS) using multiple reaction monitoring (MRM) for comprehensive quantitative and qualitative analysis of phenolic acids and flavonoid aglycones. LC-MS/MS-MRM protocols were applied for the determination of free and bound phenolics in a series of plant samples prepared from leaves and achenes (true fruits) of Japanese rose (Rosa rugosa Thunb.). The presence of large amount of phenolic compounds was detected in rose leaves (786.44 µg/g and 14.46 µg/g of phenolic acids and flavonoid aglycones, respectively). Isoferulic acid and five aglycones were revealed for the first time in this plant material. Moreover, 15 phenolic acids and six aglycones were found in the rose achenes, including eight phenolic acids and four aglycones that had not been previously reported in this rose organ. It was shown that leaves and achenes may constitute an industrially relevant source of phenolic compounds for potential commercial use in pharmaceutical, food, or cosmetic industry.

Phenolic Compounds from Nuts: Extraction, Chemical Profiles, and Bioactivity

Nuts contain a vast array of phenolic compounds having important biological properties. They include substances allocated into the five major groups named phenolic acids, flavonoids, tannins, phenolic lignans, and stilbene derivatives. The complexity in composition does not allow for setting a universal extraction procedure suitable for extraction of all nut phenolics. The use of non-conventional extraction techniques, such as those based on microwave, ultrasound, and compressed fluids, combined with generally recognized as safe solvents is gaining major interest. With regard to the latter, ethanol, water, and ethanol-water mixtures have proven to be effective as extracting solvents and allow for clean, safe, and low-cost extraction operations. In recent years, there has been an increasing interest in biological properties of natural phenolic compounds, especially on their role in the prevention of several diseases in which oxidative stress reactions are involved. This review provides an updated and comprehensive overview on nut phenolic extraction and their chemical profiles and bioactive properties.

Cellular evaluation of the antioxidant activity of U.S. Pecans [Carya illinoinensis (Wangenh.) K. Koch]

Clinical trials show an inverse relationship between the consumption of antioxidant-rich tree nuts and the development of chronic diseases. This study examined antioxidant efficacy of U.S. pecans using a modified cellular antioxidant activity (CAA) assay with comparisons to data from in vitro antioxidant assays (hydrophilic-oxygen radical absorbance capacity {H-ORAC_FL} and ferric reducing antioxidant power {FRAP}). Crude phenolic extracts from both raw and roasted pecans were analyzed. In the CAA assay, pecan phenolics were taken up by human colorectal adenocarcinoma (Caco-2) cells and bestowed CAA, determined by monitoring the fluorescence of 2',7'-dichlorofluorescein. Phenolics (25-100 μg/mL) demonstrated a reduction in fluorescence by 37-69% for raw and 26-68% for roasted pecans. The primary active phenolic constituents were determined by high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) to be epi(catechin) dimers and trimers. These oligomeric procyanidins, ranging in size from 560 to 840 g/mol appear to be small enough for cellular uptake, showing pecans are an effective antioxidant in biological systems, regardless of roasting.

Tart cherry consumption with or without prior exercise increases antioxidant capacity and decreases triglyceride levels following a high-fat meal

Exercise and high-phytonutrient foods may lower oxidative stress and increase antioxidant levels, which could combat the negative effects associated with a high-fat (HF) meal. The objective of this study is to test the effects of Montmorency tart cherry (Prunus cerasus L.) consumption, with or without aerobic exercise, on antioxidant responses to an HF meal. Twelve normal-weight men (aged 22 ± 3 years), participated in a randomized crossover design comprising 4 trials: (i) HF meal with Montmorency tart cherry consumption (MC), (ii) HF meal with placebo (P), (iii) exercise prior to HF meal with MC (E+MC), and (iv) exercise prior to HF meal with P (E+P). The HF meal contained 60 g of fat and was consumed with MC or P. For exercise trials, a 30-min bout of submaximal treadmill exercise was performed the afternoon prior to HF meal consumption. Antioxidant capacity and triglycerides (TG) levels were measured at baseline and at 1, 2, and 3 h postprandially. Postprandial antioxidant capacity as assessed by oxygen radical absorbance capacity was significantly higher after MC and E+MC compared with E+P (incremental area under the curve (iAUC): 2.95 ± 2.19 and 4.87 ± 1.45 vs. -1.02 ± 1.72 mmol Trolox equivalents/L for MC and E+MC vs. E+P, respectively; p < 0.01). Postprandial TG levels were significantly lower after E+MC compared with P (iAUC: 58.99 ± 19.46 vs. 107.46 ± 22.66 mmol Trolox equivalents/L for E+MC vs. P, respectively; p < 0.05). These results indicate that MC consumption alone, and in combination with prior exercise, leads to greater antioxidant capacity following an HF meal compared with prior exercise with placebo. Further, MC consumption with prior exercise led to more favorable postprandial TG levels compared with placebo.

Characterizing the phenolic constituents and antioxidant capacity of Georgia peaches

Acetonic crude phenolic extracts of six Georgia peach cultivars were prepared and separated into low- and high-molecular-weight (LMW and HMW) fractions by Sephadex LH-20 column chromatography. Further characterization via RP-HPLC-ESI-MS identified the main phenolics as hydroxycinnamates, (+)-catechin, and proanthocyanidins with degrees of polymerization up to seven. The LMW phenolics of the commercial cultivar, 'July Prince', were further chromatographed and examined by RP-HPLC-ESI-MS. Derivatives of phenolic acids and flavan-3-ols, along with eriodictyol and quercetin diglycosides, were identified. Antioxidant capacities of the LMW and HMW fractions were determined using in vitro assays. H-ORAC_FL and FRAP assays gave values of 872 to 2428 μmol Trolox eq./100 g f.w. and 309 to 432 μmol Fe²⁺ eq./100 g f.w., respectively. The total phenolics content (TPC) was also measured; correlations between TPCs and antioxidant assays indicated that the HMW fractions of peach extracts were major contributors to the antioxidant capacity of the cultivars analyzed.

Dynamic Changes in Phenolics and Antioxidant Capacity during Pecan (Carya illinoinensis) Kernel Ripening and Its Phenolics Profiles

Pecan (Carya illinoinensis) kernels have a high phenolics content and a high antioxidant capacity compared to other nuts-traits that have attracted great interest of late. Changes in the total phenolic content (TPC), condensed tannins (CT), total flavonoid content (TFC), five individual phenolics, and antioxidant capacity of five pecan cultivars were investigated during the process of kernel ripening. Ultra-performance liquid chromatography coupled with quadruple time-of-flight mass (UPLC-Q/TOF-MS) was also used to analyze the phenolics profiles in mixed pecan kernels. TPC, CT, TFC, individual phenolics, and antioxidant capacity were changed in similar patterns, with values highest at the water or milk stages, lowest at milk or dough stages, and slightly varied at kernel stages. Forty phenolics were tentatively identified in pecan kernels, of which two were first reported in the genus Carya, six were first reported in Carya illinoinensis, and one was first reported in its kernel. The findings on these new phenolic compounds provide proof of the high antioxidant capacity of pecan kernels.

Nutritional potential, chemical profile and antioxidant activity of Chichá (Sterculia striata) nuts and its by-products

The Sterculia striata nut commonly known as chichá is consumed raw or toasted inBrazil but information on its chemical composition and antioxidant activity are scarce in the literature. In this work, the nutritional composition, minerals profile, lipid composition and phenolic compounds profile of chichá nuts and its by-products (pellicle and shell) were determined. The results showed that the nuts and the cake contain considerable amount of fibers and proteins and are rich in minerals (Fe, Mn and Cu). Oleic acid was the main fatty acid (37.8%), and PPO (36.0%) and POP (15.6%) were the main triacylglycerides present in the chichá oil. The phytosterols β-sitosterol, stigmasteroland campesterol (1848.5μgg^-1, 542.2μgg^-1 and 186.3μgg^-1, respectively), and the γ-, δ-, α- and β-tocopherol (8.85; 2.10; 1.64, and 0.11mg100g^-1, respectively) were identified in the oil. The antioxidant activity (ABTS and FRAP assays) followed the order pellicle>shell>nuts (13.25 and 84.65; 8.71 and 64.3; 5.85 and 36.79μmolTEACg^-1, respectively). The main phenolic compounds identified in the extracts were ellagic and ferulic acids; ellagic and protocatechuic acids; and protocatechuic, ellagic and methoxyphenylacetic acids for the nuts, shells and pellicle, respectively. A strong positive correlation was observed between total phenolic content and antioxidant activity determined by ABTS and FRAP assays (r=0.9067, p<0.01; and r=0.9584, p<0.01; respectively). Collectively, the results showed that the chichá is a nut of high nutritional value, rich in bioactive compounds.

Phenolic profiles and antioxidant activity of Turkish Tombul hazelnut samples (natural, roasted, and roasted hazelnut skin)

The phenolic profiles and antioxidant status of hazelnut samples [natural (raw) hazelnut, roasted hazelnut, and roasted hazelnut skin] were compared. Free and bound (ester-linked and glycoside-linked) phenolic acids were examined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Comprehensive identification of phenolics was carried out using Q-exactive hybrid quadrupole-orbitrap mass spectrometer (Q-OT-MS). Samples were also assessed for their total phenolics and antioxidant activities using three different assays. Ten free and bound phenolic acids were quantified in hazelnut samples. Roasted hazelnut skin contained the highest content of total phenolic acids, followed by natural and roasted hazelnuts. The majority of phenolic acids were present in the bound form. Using a Q-OT-MS, 22 compounds were tentatively identified, 16 of which were identified for the first time in hazelnut samples. The newly identified compounds consisted of flavonoids, phenolic acids and related compounds, hydrolysable tannins and related compounds, and other phenolics. Three antioxidant assays demonstrated similar trends that roasted hazelnut skin rendered the highest activity. The present work suggests that roasted hazelnut skin is a rich source of phenolics and can be considered as a value-added co-product for use as functional food ingredient and antioxidant.

Separation of Ellagitannin-Rich Phenolics from U.S. Pecans and Chinese Hickory Nuts Using Fused-Core HPLC Columns and Their Characterization

U.S. pecans and Chinese hickory nuts possess a wide array of phenolic constituents with potential health benefits including phenolic acids and proanthocyanidins. Only limited information is available, however, on their compositions. The present study optimized the separation performance and characterized the low-molecular-weight phenolic fractions of these nuts with C18 and pentafluorophenyl (PFP) fused-core LC columns by employing a kinetic approach. Although both types of reversed-phase columns demonstrated similar performance in general, the PFP column furnished greater plate numbers and superior peak shapes for the low-molecular-weight fractions as well as overall separations of ellagic acid derivatives. The high-molecular-weight fraction of pecans, analyzed by a 3-μm HILIC column, possessed more proanthocyanidins than the Chinese hickory nuts with dimers and trimers (31.4 and 18.34 mg/g crude extract, respectively) being present at the greatest levels. Chinese hickory nuts had lower proanthocyanidin content but possessed tetramers and pentamers at 4.46 and 4.01 mg/g crude extract, respectively.

Antioxidant and Myocardial Preservation Activities of Natural Phytochemicals from Mung Bean (Vigna radiata L.) Seeds

Mung bean (Vigna radiata L.) seeds (MBS) contain abundant nutrients with biological activities. This study was aimed to isolate key bioactive components from MBS with antioxidant and myocardial preservation activities. A new flavonoid C-glycoside, isovitexin-6″-O-α-l-glucoside, and 14 known compounds were obtained. Their structures were identified by extensive 1D and 2D NMR and FT-ICR-MS spectroscopic analyses. The antioxidant activities of these compounds were evaluated. Compounds 1-5 and 7-10 displayed 2,2'-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS(•+)) scavenging activity, but only 5 and 7 exhibited 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) scavenging activity. The myocardial preservation effect of 2, 3, and MBS were investigated by measuring the serum levels of LDH, CK, and AST as well as the tissue level of MDA and SOD. The results demonstrated that 2, 3, and MBS had a significant protective effect against ISO-induced myocardial ischemia. MBS can be regarded as a potential new source of antioxidants and myocardial preservation agents.