HPLC–MS identification of phenols in hazelnut (Corylus avellana L.) kernels

Broad Target Metabolomics Revealed the Key Regulatory Mechanisms of the Effects of Trace Element Water-Soluble Fertilizer on the Growth of Corylus heterophylla × Corylus avellana Seedlings

BACKGROUND

Scientific and rational fertilizer management can not only improve the yield and quality of hazelnut (Corylus heterophylla × Corylus avellana) but also reduce the negative impact on the environment.

METHODS

Liquid Chromatography-tandem Mass Spectrometry (LC-MS/MS) technology was used to reveal the contents of various metabolites in hazelnut seedlings, and differential metabolites were screened by principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA).

RESULTS

The results showed that a total of 178 up-regulated differential metabolites (Fold change > 1) and 175 down-regulated differential metabolites (Fold change < 1) were detected in 6 comparison groups (DWF0 vs. DWF4, DWF0 vs. DWF5, DWF0 vs. DWF6, DWF4 vs. DWF5, DWF4 vs. DWF6, DWF5 vs. DWF6). Interestingly, the flavonoid metabolic pathway was dramatically enriched, and it was involved in each fertilization combination. The metabolites of the flavonoid pathway in different fertilized and unfertilized groups were compared and analyzed, which displayed that metabolites tricetin, eriodictyol, garbanzol, apigenin, and biochanin A were significantly up-regulated, while garbanzol and astraglin were significantly down-regulated. More interestingly, the determination of flavonoid content and real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) displayed that the application of trace element water-soluble fertilizer could significantly enhance the flavonoid content and the expression of genes related to the flavonoid biosynthesis pathway, such as phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H), with the DWF4 treatment displaying the most significant values.

CONCLUSIONS

Overall, the application of trace element water-soluble fertilizer (especially the DWF4 treatment) markedly affected the changes in key metabolites of the flavonoid pathway and the expression levels of key genes, thus promoting the growth and development of the hazelnut, which offers an important starting point for future analysis through genetic engineering.

Clarification of morphological traits of unexplored 'Mortarella' and 'Camponica' hazelnut cvs. From the Campania region of Italy, to enhance their shell polyphenol diversity

European hazelnuts are widely cultivated as raw materials in the food industry. Processing produces several non-value-added byproducts, e.g. pericarp and episperm. Herein, the 'Camponica' and 'Mortarella' cultivars were characterised using International Union for the Protection of New Varieties of Plants guidelines. The in-depth analysis of the chemical profiles of different particle size sieved fractions from hazelnut outer pericarps was performed following ultrasound-assisted extraction and ultra-high-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS). Total phenolic, flavonoid, and tannin contents were evaluated, as well as their radical scavenging capacity using 2,2-diphenyl-1-picrylhydrazyl and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid assays. The outer shell extracts mainly contained ellagic acid derivatives, giffonins, and flavonol glycosides. The inner pericarp and episperm differed for their exclusive epicatechin, catechin, and proanthocyanidin dimer content. The novel data provide new insights into the differences in the chemical compositions of byproducts of these hazelnut cultivars, which will be valuable for nutraceutical, cosmetic, and functional food valorisation applications.

The Role of Roasting on Changes in Oil Contents, Bioactive Properties, Polyphenol Contents and Fatty Acid Profiles of Turpentine (Pistacia terebinthus L.) Fruit and Oils

In this study, the fluctuations in the oil content, total phenol, total flavonoid, radical scavenging capacity, phenolic constituent profiles and fatty acids of turpentine fruits during roasting of turpentine fruits and oils in the oven and microwave treatments were revealed. Total phenolic amounts of turpentine fruit and oils varied between 153.57 (oven) and 197.86 mgGAE/100 g (control) to 17.68 (control) and 30.65 mg GAE/100 g (oven), respectively. Total flavonoid values of the turpentine fruit and oils were characterized to be between 370.36 (microwave) and 567.50 mg/100 g (control) to 89.64 (oven) and 227.50 mg/100 g (microwave), respectively. While quercetin values of the turpentine fruits change between 171.73 (oven) and 330.88 mg/100 g (control), rutin amounts of fruits were defined to be between 3.66 (oven) and 10.00 mg/100 g (control). Catechin amounts of the turpentine fruits roasted in oven and microwave were specified to be between 3.42 (microwave) and 13.69 mg/100 g (oven). Oleic and linoleic acid contents of the oils extracted from raw and roasted turpentine fruits were assessed to be between 50.19 (oven) and 51.30% (control) to 22.89 (control) and 23.39% (oven), respectively. As a result, the phenolic components of turpentine oils were generally higher than those of turpentine fruits.

Oil Composition and Phenolic Compounds of Plum Seeds Obtained from Fruit Processing By-products Treated by Heat

In this study, the effect of microwave drying on oil content, bioactive compounds, antioxidant activity, polyphenols and fatty acid profiles of fresh (control) and dried plum kernels was investigated. The oil quantities of plum seeds dried were found between 27.40% (control) and 42.42% (900 W). Total phenolic and flavonoid values of fresh (control) and dried-plum seeds were assessed to be between 9.77 (control) and 41.66 mgGAE/100 g (900 w) to 6.90 (control) and 23.67 mg/100 g (900 W), respectively. Total phenol and flavonoid quantities of the plum seeds dried at 900 W were slightly higher than those of the plum seeds dried at 720 W. L* (brightness) values of plum seeds changed between 55.97 and 59.62. Roasting in the microwave oven at 720 W was decreased the L* values of samples, while L* value of sample roasted at 900 W was closed to control. Gallic and 3,4-dihydroxybenzoic acid values of plum kernel samples were assigned to be between 1.19 (720 W) and 2.01 mg/100 g (900 W) to 0.22 (control) and 7.09 mg/100 g (900 W), respectively. Also, catechin and rutin quantities of plum seeds were established between 0.20 (control) and 7.55 mg/100 g (900 W) to 1.42 (control) and 3.59 mg/100 g (900 W), respectively. In general, the amount of phenolic compounds of plum seeds dried at every two watts showed an increase (except quercetin) compared to the control. Only the amount of quercetin decreased partially in the dried samples. While oleic acid quantities of raw (control) and dried plum kernel oils are reported between 68.28% (720 W) and 71.60% (900 W), linoleic acid amounts of plum kernel oils were found between 20.77% (900 W) and 23.49% (720 W). The quantities of saturated fatty acids in plum kernel oils were found to be quite low compared to the content of unsaturated fatty acids.

The Role of Microwave and Oven Roasting on Oil Contents, Bioactive Properties, Phenolic Components, Fatty Acids and Mineral Contents of Grape (Vitis spp.) Seeds

In this study, the role of roasting on the total phenol, antioxidant capacity, phenolic constituents and fatty acid profile of the grape seeds was investigated. Total phenolic and flavonoid quantities of the grape seeds roasted in microwave (MW) and conventional oven (CO) systems were recorded between 673.57 (control) and 713.57 (MW) to 7121.67 (MW) and 7791.67 mg/100 g (CO), respectively. Antioxidant activities of the grape seeds varied between 6.57 (MW) and 7.24 mmol/kg (control). Catechin and rutin quantities of the grape seeds were recorded to be between 435.30 (CO) and 581.57 (control) to 94.94 (CO) and 110.53 mg/100 g (MW), respectively. While gallic acid amounts of the seed samples are established between 21.06 (control) and 101.79 (MW), quercetin values of the grape seeds were assigned to be between 56.59 (control) and 77.81 mg/100 g (CO). In addition, p-coumaric acid and resveratrol quantities of the grape seeds were recorded between 15.43 (control) and 22.98 (CO) to 12.50 (CO) and 29.57 mg/100 g (MW), respectively. The main fatty acids in oil samples were linoleic, oleic, palmitic and stearic acids in decreasing order. Linoleic and oleic acid values of the oils provided from grape seeds were recorded to be between 72.75 (control) and 73.33% (MW) to 14.79 (CO) and 14.87% (MW), respectively. It was observed that the element results related to the grape seed differed based on the roasting type when compared to the control. The most abundant elements in the grape seed were K, P, Mg, S, Na, Fe, Ca, Zn, and K and P amounts of the grape seeds were reported to be between 6706.93 (MW) and 7089.33 (control) to 2764.27 (CO) and 2927.97 mg/kg (control), respectively. It is thought that it would be beneficial to add grape seeds to foods as an ingredient by taking into account these phytochemical components as a result of the applied heat treatment.

Amplifying Bioactivity of blue honeysuckle (Lonicera caerulea L.) fruit puree through Ultrasonication: Antioxidant and antiproliferative activity

Blue honeysuckle (Lonicera caerulea L.) serves as a significant reservoir of polyphenol compounds. This impact of ultrasonication processing on the bioaccessibility of blue honeysuckle fruit puree during in vitro digestion was evaluated. The polyphenol compounds, antioxidant capacity and antiproliferative activity were measured, with a particular focus on determining the total proanthocyanidin content of the puree during digestion. The results revealed that the U300 W treatment significantly increased antioxidant content and enhanced the stability of antioxidant capacity, leading to stronger antiproliferative activity. A total of 33 compounds, including 14 phenolic acids, 5 flavanols, 1 flavanol-3-ol, 1 flavanone alcohol, 3 flavanones, 1 flavanone, and 8 non- polyphenols were found in both untreated and ultrasonicated puree during in vitro digestion. The untreated puree contained 22 compounds, while the ultrasonicated puree contained 33. Compared to untreated samples, ultrasonicated samples contained significantly higher levels of loganic acid, dihydrokaempferol, kaempferol derivatives, and plantagoside. Except for vanillic acid, citric acid, protocatechuic acid, and luteolin-4'-O-glucoside, the polyphenols showed a decreasing trend during oral-gastric-small intestinal-colon digestion. The U500 W ultrasonicated fruit puree exhibited the strongest antiproliferative activity. Overall, the results demonstrated that ultrasonication has the potential to enhance the bioaccessibility of antioxidant compounds and the antiproliferative activity of blue honeysuckle fruit puree.

Artificial intelligence decision making tools in food metabolomics: Data fusion unravels synergies within the hazelnut (Corylus avellana L.) metabolome and improves quality prediction

This study investigates the metabolome of high-quality hazelnuts (Corylus avellana L.) by applying untargeted and targeted metabolome profiling techniques to predict industrial quality. Utilizing comprehensive two-dimensional gas chromatography and liquid chromatography coupled with high-resolution mass spectrometry, the research characterizes the non-volatile (primary and specialized metabolites) and volatile metabolomes. Data fusion techniques, including low-level (LLDF) and mid-level (MLDF), are applied to enhance classification performance. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) reveal that geographical origin and postharvest practices significantly impact the specialized metabolome, while storage conditions and duration influence the volatilome. The study demonstrates that MLDF approaches, particularly supervised MLDF, outperform single-fraction analyses in predictive accuracy. Key findings include the identification of metabolites patterns causally correlated to hazelnut's quality attributes, of them aldehydes, alcohols, terpenes, and phenolic compounds as most informative. The integration of multiple analytical platforms and data fusion methods shows promise in refining quality assessments and optimizing storage and processing conditions for the food industry.

Does hazelnut consumption affect brain health and function against neurodegenerative diseases?

INTRODUCTION

A healthy daily diet and consuming certain nutrients, such as polyphenols, vitamins, and unsaturated fatty acids, may help neuronal health maintenance. Polyphenolic chemicals, which have antioxidant and anti-inflammatory properties, are involved in the neuroprotective pathway. Because of their nutritional value, nuts have been shown in recent research to be helpful in neuroprotection.

OBJECTIVE

Hazelnut is often consumed worldwide in various items, including processed foods, particularly in bakery, chocolate, and confectionery products. This nut is an excellent source of vitamins, amino acids, tocopherols, phytosterols, polyphenols, minerals, and unsaturated fatty acids. Consuming hazelnut may attenuate the risk of neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and Huntington's disease due to its anti-inflammatory and anti-oxidant qualities.

RESULTS

Many documents introduce hazelnut as an excellent choice to provide neuroprotection against neurodegenerative disorders and there is some direct proof of its neuroprotective effects.

DISCUSSION

So hazelnut consumption in daily diet may reduce neurodegenerative disease risk and be advantageous in reducing the imposed costs of dealing with neurodegenerative diseases.

The Role of Heating Treatments on Bioactive Compounds, Fatty Acid Compositions, Phenolic Compounds and Mineral Contents of Peanut Kernels

In this study, the role of boiling and roasting on chemical properties, fatty acid compositions, polyphenols and mineral contents of peanut kernels provided from Mersin (Silifke) province in Turkey was investigated. The oil yields of peanut kernels treated were specified between 48.92% (boiled) and 52.93% (oven roasting). While total phenolic quantities of raw, boiled and roasted-peanut kernels were assessed between 71.98% (boiled) and 178.81 mgGAE/100 g (raw(control)), total flavonoid quantities of treatedpeanut kernels were found to be between 120.36 (boiled) and 530.36 mgQE/100 g (control). The antioxidant activities of peanut kernels ranged from 2.66 (microwave roasting) to 3.90 mmolTE/kg (control). The phenolic constituents of peanut kernels are sensitivities to heat treatment. The maximum reduction in the phenolic compounds of peanut kernels was determined in the peanut kernels roasted in the microwave and oven roasting systems, and followed by the boiled process in decreasing order. Also, while oleic acid quantities of raw, boiled and roasted-peanut kernel oils are determined between 54.06% (boiled) and 57.22% (microwave roasting), the linoleic acid quantities of the oils of peanut kernels treated were specified between 25.18% (microwave roasting) and 27.33% (boiled). The composition of the oil of the peanut kernels roasted in microwave has highly increased (except palmitic and linoleic acids) according to the control. The macro elements found at the highest amounts in raw, boiled and roasted-peanut kernels were P, K, Ca, Mg, S and Na. The most available as micro element has been Fe and Zn. Heat treatments such as roasting and boiling not only change the visible rawness of peanuts, but they can also subsequently cause chemical changes in peanut kernels.

Hazelnut and its by-products: A comprehensive review of nutrition, phytochemical profile, extraction, bioactivities and applications

As output of hazelnut increases worldwide, so does the amount of by-products, leading to huge waste and environmental stress. This paper focuses on the varieties of hazelnut that have been studied more in the past two decades, and summarizes the research status of hazelnut and its by-products from the aspects of nutritional value, phytochemicals, extraction methods, biological functions and applications. Hazelnut and its by-products are rich in a variety of bioactive constituents, mainly polyphenols, which have antioxidant, antibacterial and prebiotic effects. Moreover, hazelnut shells, husks, and leaves contain taxanes such as paclitaxel, which can inhibit the proliferation of cancer cells. They are potentially good natural sources of paclitaxel compared to the slower growing yew. Therefore, it is essential to further integrate the extraction techniques and health-promoting properties of these nutrients and bioactive substances to expand their application and enhance their value.

Foliar Nutrition Influences Yield, Nut Quality and Kernel Composition in Hazelnut cv Mortarella

In hazelnut, foliar nutrition is utilized globally to integrate microelement deficiencies and optimize their assimilation and effects on yield performances. Nevertheless, nut quality and kernel composition can be positively affected by foliar nutrition. Recently, several studies pointed out the need for increasing the sustainability of orchard nutrition by proposing the management of not only micronutrients, but also main components, such as nitrogen, through foliar spraying. In our study, different foliar fertilizers were used to understand the effectiveness of supporting hazelnut productivity and nut and kernel quality. Water was used as a control. Foliar fertilizations affected tree annual vegetative growth, improved kernel weight and decreased the incidence of blanks compared to the control. Differences in fat, protein, and carbohydrate concentration were also found among treatments, with increased fat concentrations and total polyphenols content in fertilized treatments. Foliar fertilization improved the oil composition of the kernels, though fatty acid composition responded differently to nutrients spray. Oleic acid concentration was promoted, while palmitic acid concentration was reduced in fertilized plants compared to control trees. Furthermore, CD and B trees were characterized by an increase in the ratio of unsaturated/saturated fatty acids compared to untreated trees. Finally, foliar spraying improved lipid stability compared to the control due to higher total polyphenol concentration.

The Effects of the Cultivar and Environment on the Phenolic Contents of Hazelnut Kernels

Different climatic conditions are known to affect the synthesis of primary and secondary metabolites. Therefore, the phenolic contents in new growing areas could affect the quality and flavor of hazelnuts. The aim of this study was to determine the variability of the phenolic contents of the kernels in different commercial hazelnut cultivars depending on their growing area. Five cultivars ('Tonda Gentile delle Langhe', 'Merveille de Bollwiller', 'Pauetet', 'Tonda di Giffoni', and 'Barcelona' (syn. 'Fertile de Coutard')) grown in different European collection orchards were included in the study. High-performance liquid chromatography coupled with mass spectrometry was used to identify and quantify the phenolic compounds. Thirteen phenols were identified in the hazelnut kernels, including 7 flavanols, 2 hydroxybenzoic acids, 3 flavonols, and one dihydrochalcone. Catechin and procyanidin dimers were the main phenolic compounds found in the hazelnut kernels. The highest contents of catechin and total flavanols were determined in cultivars cultivated in Spain and northern Italy, and the lowest in Slovenia and France. Flavanols were the major phenolic groups independent of the place of cultivation, as they accounted for more than 50% of all phenolic compounds identified. The flavanols were followed by hydroxybenzoic acids, flavonols, and dihydrochalcones. Higher contents of flavanols and flavonols were found in kernels from areas characterized by higher natural irradiation, which stimulates their accumulation. The contents of hydroxybenzoic acids correlated with altitude, which stimulated phenolic acid synthesis. A negative correlation was observed between the dihydrochalcone content and annual rainfall, probably due to hydric stress.

The Content of Phenolic Compounds and Mineral Elements in Edible Nuts

Edible nuts are an important component of a healthy diet, and their frequent consumption has beneficial impact on human health, including reducing the risk of cardiovascular and neurodegenerative diseases. Moreover, various factors, including cultivar, climate, soil characteristic, storage and treatment have influence on the chemical composition of nuts. Therefore, nine tree nut types and peanuts commonly available on Polish market were evaluated for phenolic profile and mineral elements content. The concentration of individual phenolic compounds, including flavonoids, aromatic acids and caffeic acid phenethyl ester (CAPE) was determined by ultra-high pressure liquid chromatography, while the content of macro-elements and trace minerals was analyzed by atomic absorption spectrometry. The phenolic profile of analyzed nuts substantially varied depending on the type of nut. The highest total content of all analyzed flavonoids was determined in walnuts (114.861 µg/g), while the lowest in almonds (1.717 µg/g). In turn, the highest total content of all tested aromatic acid was determined in pecans (33.743 µg/g), and the lowest in almonds (0.096 µg/g). Epicatechin and cinnamic acid were detected in the highest concentration in tested nuts. Moreover, in examined nuts (except walnuts and Brazil nuts), the presence of CAPE was confirmed. The tested nuts were also characterized by wide variation in element concentrations. Almonds contained high concentration of macro-elements (13,111.60 µg/g), while high content of trace elements was determined in pine nuts (192.79 µg/g). The obtained results indicate that the tested nuts are characterized by a significant diversity in the content of both phenolic compounds and minerals. However, all types of nuts, apart from the well-known source of fatty acids, are a rich source of various components with beneficial effect on human health.

Pomegranate Fruit Quality and Seed Drying Method: Effect on the Chemical Composition and Bioactivities of the Extracted Oil

The study presents a comparative investigation of the composition and bioactivity of oil extracted from pomegranate seeds of sun-burned fruit (SB) and healthy fruit (HF) for the value-adding potential of pomegranate fruit waste. Seeds from SB and HF were independently freeze dried, sun dried, and oven dried before ultrasound-assisted oil extraction using petroleum ether. The extracted oil was analysed for yield, refractive index, ρ-anisidine value, total phenolic content (TPC), DPPH radical scavenging ability, antimicrobial activity, tyrosinase enzyme inhibition ability, and fatty acid composition. The results showed that oven dried seeds, regardless of fruit quality, yielded the highest oil (20.85–24.70%, dry weight). Regardless of the seed drying method, oil from the seeds of SB exhibited the highest TPC (1.48–2.84 mgGAE/g PSO) than oil from the seeds of HF. The oil from oven dried and freeze dried seeds of SB were more effective in scavenging the DPPH radicals with IC50 values of 34.77 and 39.97 µg/mL, respectively. All the oil samples showed good ability to inhibit tyrosinase enzyme regardless of fruit quality and seed drying method, with monophenolase and diphenolase IC50 ranging between 0.31 and 0.49 mg/mL and 0.64 and 2.43 mg/mL, respectively. Irrespective of the drying method, oil extracted from HF seeds exhibited greater antimicrobial potency against the tested bacteria. The fatty acid composition of the oil samples was neither affected by fruit quality and seed drying method. Generally, all oil samples exhibited high levels of punicic acid (81.21–82.68%) and low omega 6 to omega 3 ratios (0.19–0.37%), suggesting that the oil samples were healthy. Principal component analysis (PCA) established that freeze dried seeds of SB is an excellent source of oil with higher TPC, punicic acid, polyunsaturated fatty acids, and unsaturated fatty acid/saturated fatty acid ratio. It can be concluded that the seed from SB is a good raw material for oil that can be utilised in cosmetic products formulation.

Kernel Nutrient Composition and Antioxidant Ability of Corylus spp. in China

Hazelnut (Corylus) is an important woody oil tree species in economic forests. China, as one of the original countries of native Corylus species, had 8 species and 2 varieties. However, little information is available on the hazelnut nutritional quality of these Chinese Corylus species. In this study, four main wild Corylus species (C. heterophylla Fisch., C. mandshurica Maxim., C. kweichowensis Hu., and C. yunnanensis Franch.) originating in China and one main cultivar of hybrid hazelnut (Corylus heterophylla Fisch. × C. avellana L.) cv. 'Dawei' from China were used to analyze the basic nutritional composition (content of oil, fatty acid, protein, saccharide, aminao acid, vitamin C, tocopherol, total phenols, and total flavonoids) and antioxidant ability. The results showed that oil content ranged from 52.97 to 60.88 g/100 g DW and highly unsaturated fatty acid (UFA) content was over 91%. Oleic was the most dominant UFA in these hazelnut kernels, and the relative content was ranging from 71.32 to 85.19%. Compared with other four hazelnut kernels, C. heterophylla Fisch. was the lowest oil content of hazelnut with lower oleic acid content and higher linoleic acid content, obviously. The total protein content ranged from 13.15 to 18.35 g/100 g DW, and all amino acids were detected as hydrate amino acids, but Tryptophan, an essential amino acid, was not detected as free amino acid in these hazelnut kernels. Kernel of C. heterophylla Fisch. was with the highest content of protein and amino acid. Saccharose was the most essential and abundant disaccharide in the hazelnut kernels. C. mandshurica Maxim. was the highest saccharide content among these hazelnut kernels. α-tocopherol was the main type of tocopherol found in the hazelnut kernels. Wild hazelnut kernels generally had higher bioactivity substance content (vitamin C, total tocopherol, total phenol and total flavonoid) and antioxidant capacity. Compared to the four wild hazelnut kernels, the hybrid hazelnut cv. 'Dawei' had higher content of oil, oleic acid, α-tocopherol and sugar. Overall, there were great differences in the nutritional composition of different hazelnut species. Wild species are a good source of breeding materials because of their own characteristics in nutrition composition, and the hybrid hazelnut cv. 'Dawei' with good quality has the value of commercial promotion.

Combined Spraying of Boron and Zinc During Fruit Set and Premature Stage Improves Yield and Fruit Quality of European Hazelnut cv. Tonda di Giffoni

Boron (B) and zinc (Zn) are essential micronutrients of plant nutrition programs in orchards for securing the crop quality and yield. Although orchard supplementation with B and Zn is a common practice to overcome deficiencies or maintain their optimal levels, the efficiency of combined B and Zn spraying in relation to European hazelnut (Corylus avellana L.) phenological stage has not been investigated so far. Leaf and kernel mineral and functional traits were studied in cultivar Tonda di Giffoni after B and Zn spraying in four phenological stages. During the 2016/2017 season, 9-year-old trees were sprayed with B (0, 800, and 1,600 mg L^-1) and Zn (0, 400, and 800 mg L^-1) under three treatments: B₀+Zn₀, B₈₀₀+Zn₄₀₀, and B₁₆₀₀+Zn₈₀₀ implemented in three spring application programs scheduled from October to December (P1: four times, P2: early two times, and P3: late two times). B and Zn treatments in P1 and P3 led to higher Zn concentration both in leaves and in kernels compared with non-sprayed trees. Stabilized nut production increased 2.5-fold under B₈₀₀+Zn₄₀₀ in all three programs. Kernel/nut ratio improved in both B+Zn treatments in P1 and P3, while the percentage of blank nuts was reduced compared with B₀+Zn₀. Increased radical scavenging activity in B+Zn-treated kernels and leaves was not attributed to the accumulation of phenolics in P3 compared with B₀+Zn₀, whereas B and Zn spraying reduced the level of lipid peroxidation in both studied organs. According to the results, combined B and Zn should be sprayed at the end of spring (P3) on hazelnut plantations in temperate areas such as Southern Chile, whereas early applications (P2) showed an irregularity in nut production and functional traits in nuts. Moderate and partialized rates of B and Zn and the time of implementation contribute to improving the quantitative and qualitative features crucial for future sustainable hazelnut production.

Phenolic Compounds, Antioxidant Activity and Fatty Acid Composition of Roasted Alyanak Apricot Kernel

The oil recovery from Alyanak apricot kernel was 36.65% in control (unroasted) and increased to 43.77% in microwave-roasted kernels. The total phenolic contents in extracts from apricot kernel were between 0.06 (oven-roasted) and 0.20 mg GAE/100 g (microwave-roasted) while the antioxidant activity varied between 2.55 (oven-roasted) and 19.34% (microwave-roasted). Gallic acid, 3,4-dihydroxybenzoic acid, (+)-catechin and 1,2-dihydroxybenzene were detected as the key phenolic constituents in apricot kernels. Gallic acid contents varied between 0.53 (control) and 1.10 mg/100 g (microwave-roasted) and 3,4-dihydroxybenzoic acid contents were between 0.10 (control) and 0.35 mg/100 g (microwave-roasted). Among apricot oil fatty acids, palmitic acid contents ranged from 4.38 (oven-roasted) to 4.76% (microwave-roasted); oleic acid contents were between 65.73% (oven-roasted) and 66.15% (control) and linoleic acid contents varied between 26.55 (control) and 27.12% (oven-roasted).

Choline Chloride-Lactic Acid-Based NADES As an Extraction Medium in a Response Surface Methodology-Optimized Method for the Extraction of Phenolic Compounds from Hazelnut Skin

Deep eutectic solvents (DESs) are promising green solvents for the extraction of compounds from food byproducts. Hazelnut (Corylus avellana L.) is one of the most commonly cultivated tree nuts worldwide. The skin represents one of the major byproducts of the hazelnut industry and accounts for 2.5% of the total hazelnut kernel weight. It is a rich source of phenolic compounds like flavan-3-ols, flavonols, dihydrochalcones, and phenolic acids. In this work, fifteen DESs based on choline chloride and betaine, with different compositions, were studied in order to test their phenolic compounds extraction efficiency through the determination of their total concentration via Folin–Ciocalteu assay. A qualitative analysis of extracted phenolic compounds was assessed by HPLC with UV and MS detection. Using the DES with the best extraction efficiency, a new ultrasound-assisted solid liquid extraction (UA-SLE) method was optimized though the response surface methodology (RSM), taking into account some extraction parameters. Efficient recovery of extracted phenolic compounds was achieved using a 35% water solution of choline chloride and lactic acid (molar ratio 1:2) as an extraction solvent, working at 80 °C and with a solid-to-solvent ratio of 1:25 gmL⁻¹. The optimized conditions made it possible to recover 39% more phenolic compounds compared to a classic organic solvent.

Enhanced Recovery of Phenolic and Tocopherolic Compounds from Walnut (Juglans Regia L.) Male Flowers Based on Process Optimization of Ultrasonic Assisted-Extraction: Phytochemical Profile and Biological Activities

The extraction of bioactive compounds present in walnut (Juglans regia L.) male flowers (WMFs) was performed based on an experimental design using ultrasonic-assisted extraction. Solvent nature, extraction time, and water content were selected as experimental variables, and phenolic, flavonoidic, and condensed tannins contents and antioxidant properties were evaluated. Acetone was the solvent with the highest extraction performance, with the extracts obtained using this solvent displaying an increased concentration of bioactive compounds and increased antioxidant activities. For several extracts with high bioactive content, individual polyphenolic and tocopherolic compounds were evaluated by means of LC-MS and LC-MS/MS. The best extraction conditions for polyphenolic (2.86 mg gallic acid equivalents/g WMF) and tocopherolic compounds (29.4 µg/g WMF) were acetone with 40% water content (N20) and acetone with 20% water content (N15), respectively. Although the total tocopherol concentrations were lower than in other Juglans regia parts, most of the total tocopherol quantity was provided by the highly biologically active δ-tocopherol (84%). Significant quantities of quercetin (101.9 µg/g), hyperoside (2662.9 µg/g), quercitrin (405.7 µg/g), and isoquercitrin (1293.7 µg/g) were determined in WMF (N20). Both extracts inhibited the enzymatic activity of α-glucosidase and tyrosinase; however, an increased inhibition was observed for N20, the extract with the higher polyphenolic content. Conversely, N15 had higher anticancerous activity on the cell lines used, with a moderate selectivity towards the cancerous phenotype being observed for both extracts. At non-cytotoxic concentrations, both extracts displayed good antioxidant activities in cellular cultures, decreasing basal and H₂O₂-induced oxidative stress. This is the first characterization of both hydrophilic and lipophilic phytochemicals in WMF extracts. The outcomes of our study reveal that walnut male flowers have strong biological activities, thus justifying further research to demonstrate their usefulness in the food, pharmaceutical, and/or cosmetic industries.

A comprehensive review on different classes of polyphenolic compounds present in edible oils

Edible oils are used as a frying medium and in the preparation of several food products. They are mainly constituting triacylglycerols as major components, while other compounds are classified as minor constituents, which include polyphenols. This class of compounds plays an important role in the thermal stability and quality attributes of the finished industrial food products. In addition to other antioxidants, the desired thermal stability of edible is achieved by either fortification or mixing of edible oils. This comprehensive review was therefore aimed to review the different classes of polyphenolic compounds present in commonly consumed edible oils. The edible oils reviewed include soybean, olive, rapeseed, canola, sunflower, flaxseed, sesame, cottonseed, palm, almond, peanut, chestnut, coconut, and hazelnut oils. The identified classes of polyphenolic compounds such as simple phenols, hydroxybenzoic acids, phenylethanoids, hydroxycinnamic acid, esters of hydroxycinnamic acids, coumarins & chromans, stilbenes, flavonoids, anthocyanins, and lignans were discussed. It was observed that a single edible from different origins showed the varied composition of the different classes of phenolic compounds. Among the oils, soybean, sunflower, olive, and brassica oils received higher attention in terms of polyphenol composition. Some classes of phenolic compounds were either not reported or absent in one edible oil, while present in others. Among the different classes of phenolics, hydroxybenzoic acids, hydroxycinnamic acid and flavonoids were the most widely present compounds. Phenolic compounds in edible oils possess several health benefits such as antioxidant, antibacterial, anti-viral, anti-inflammatory, anti-tumour, antioxidants, cardioprotective, neuroprotective, anti-diabetic properties and anti-obesity.

Antioxidant and Antiglycation Effects of Polyphenol Compounds Extracted from Hazelnut Skin on Advanced Glycation End-Products (AGEs) Formation

The advanced glycation end-products (AGEs) arise from non-enzymatic reactions of sugar with protein side chains, some of which are oxido-reductive in nature. Enhanced production of AGEs plays an important role in the pathogenesis of diabetic complications as well as in natural aging, renal failure, oxidative stress, and chronic inflammation. The aim of this work is to study antiglycation effects of polyphenol compounds extracted by hazelnut skin that represents an example of polyphenols-rich food industry by-product, on AGEs formation. AGEs derived from incubation of bovine serum albumin (BSA) and methylglyoxal (MGO) were characterized by fluorescence. The phenolics identification and total polyphenol content in hazelnut skin extracts were analyzed by HPLC-MS and the Folin–Ciocalteu method, respectively. Antioxidant efficacy was evaluated by monitoring total antioxidant activity to assess the ABTS radical scavenging activity of samples by TEAC assay and oxygen radical absorbance capacity (ORAC) assay, expressed as millimoles of Trolox equivalents per gram of sample. Data here presented suggest that phenolic compounds in hazelnut skin have an inhibitory effect on the BSA-AGEs model in vitro, and this effect is concentration-dependent. The putative role of the hazelnut skin antioxidative properties for hindering AGEs formation is also discussed. Because of AGEs contribution to the pathogenesis of several chronic diseases, foods enriched, or supplements containing natural bioactive molecules able to inhibit their production could be an interesting new strategy for supporting therapeutic approaches with a positive effect on human health.

Bioactive compounds, nutritional and sensory properties of cookies prepared with wheat and tigernut flour

This study aimed to evaluate cookies made with wheat (0%, 80%, 60%, and 50%) and tigernut flour (0%, 20%, 40%, and 50%) from two different sources. Standard methods were applied to determine the chemical properties, phenolic component, fatty acid composition, mineral content, and sensory properties of cookies. Tigernut flour from both sources was rich in oil, and total and individual phenolics, but with low antioxidant activity compared to wheat flour. The addition of tigernut flour to wheat resulted in increase of the content of bioactive compounds, minerals, and fatty acid contents of cookies. The cookies produced by formulating wheat with tigernut had a comparable organoleptic quality scores to wheat flour cookies. The production of cookies with both wheat and tigernut flour showed that this mixture is an interesting opportunity to have a functional product rich in bioactive compounds and considered satisfactory by consumers.

Effect of sonication process of terebinth (Pistacia terebinthus L.) fruits on antioxidant activity, phenolic compounds, fatty acids and tocopherol contents

The current study investigated the impact of sonication process on antioxidant activity, phenolic compounds, total phenolic, total flavonoid, oil contents, fatty acids profile, and tocopherols of terebinth (Pistacia terebinthus) fruits. The highest antioxidant activity (87.32%), total phenolic (251.25 mg/100 g) and flavonoid (3413.72 mg/100 g) contents were observed in terebinth fruits sonicated for 30 min. The oil contents of terebinth increased from 38.93% (control) to 42.60% (sonicated for 15 min) after sonication process. The quercetin and catechin were the chief phenolic compounds in P. terebinthus extracts and their values were increased from 129.09 to 467.28 mg/100 g (quercetin) and from 5.58 to 21.33 mg/100 g (catechin) in fruits sonicated for 30 min. The major fatty acids of terebinth fruit oil were oleic (48.02-49.15%), linoleic (22.28-23.48%) and palmitic (22.10-23.67%) and sonication processes did not affect the quantities of these fatty acids. γ-Tocopherol was the most abundant isomer with the value of 63.95-122.03 mg/100 g in terebinth fruit oil. It could be concluded that pre-sonication for 30 min was more suitable for enhancing the antioxidants and phenolic compounds of P. terebinthus fruit.

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.

Enhanced Recovery of Antioxidant Compounds from Hazelnut (Corylus avellana L.) Involucre Based on Extraction Optimization: Phytochemical Profile and Biological Activities

Tree nut by-products could contain a wide range of phytochemicals, natural antioxidants, which might be used as a natural source for dietary supplements. The aim of the present study was to evaluate the phenolic and sterolic composition, as well as the antioxidant and other biological activities, of hazelnut involucre (HI) extracts. Experimental designs were developed in order to select the optimum extraction conditions (solvent, temperature, time) using turbo-extraction by Ultra-Turrax for obtaining extracts rich in bioactive compounds. Qualitative and quantitative analyses were performed by LC-MS and LC-MS/MS and they revealed important amounts of individual polyphenols and phytosterols, molecules with antioxidant potential. The richest polyphenolic HI extract with the highest antioxidant activity by TEAC assay was further evaluated by other in vitro antioxidant tests (DPPH, FRAP) and enzyme inhibitory assays. Additionally, the cytotoxic and antioxidant effects of this extract on two cancerous cell lines and on normal cells were tested. This is the first study to analyze the composition of both hydrophilic and lipophilic bioactive compounds in HI extracts. Our findings reveal that this plant by-product presents strong biological activities, justifying further research, and it could be considered an inexpensive source of natural antioxidants for food, pharmaceutical, or cosmetic industry.

Effects of hazelnut skin addition on the cooking, antioxidant and sensory properties of chicken burgers

The aim was to evaluate the effects of hazelnut skin (HS) addition on the oxidation and sensorial properties of chicken burgers during storage and after cooking. Burgers were prepared and divided in five groups: [C] control without HS addition, [CAA] control with ascorbic acid, and [HS1] 1%, [HS2] 2% and [HS3] 3% HS addition. Burgers for each batch were prepared in triplicate and analysed raw and cooked after 1 and 4 days of refrigerated storage (4 ± 1 °C), respectively. Lipid oxidation was assessed by monitoring malonaldehyde formation with a 2-thiobarbituric acid reactive substances assay, and antioxidant capacity was assessed with 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods. A sensory evaluation was performed by twenty experienced panellists, and the attributes that were measured were: colour, greasiness, flavour, odour, juiciness, granulosity, chewiness and overall acceptability. Lipid oxidation values were higher in the HS burgers than in the C and CAA burgers, except for the cooked burgers at day 4. HS addition had a significant effect with a decrease in diameter and an increase in fat retention. In all treatments, FRAP was lower in the C and HS groups than in the CAA group, except for cooked burgers at day 4, where the values of the HS2, HS3 and CAA groups were similar. The DPPH assay showed higher values on both days for the raw and cooked burgers treated with CAA or HS compared to the control group. HS addition influenced only meat colour among the sensorial parameters that were considered.

Changes in phenolic profiles of red-colored pellicle walnut and hazelnut kernel during ripening

In studies of secondary metabolites in nuts, many constituents in the kernel remain unidentified due to a high content of phenolic compounds in the pellicle. In the present study, we focused on the investigation of the phenolic and dicarboxylic acid profiles of walnut and hazelnut pellicle-less kernels. High-performance liquid chromatography with diode array and mass spectrometric detection (HPLC-DAD-MSn) was used to carry out the determination of individual phenolics and dicarboxylic acids in brown and red-pellicle walnut and hazelnut. Results show that hexahydroxydiphenic acid (HHDP) di-galloyl hexose isomer, vanillic acid hexoside, quinic acid derivative and catechin are the main constituents of the phenolic profile of walnut, while galloylquinic derivative, caffeoyl hexoside and catechin are the main constituents of the hazelnut kernel. Even though both walnut and hazelnut kernels have a considerably lower content of phenolic compounds and dicarboxylic acids in comparison to the pellicles, when calculated as a percentage of the total mass, the kernel makes a significant contribution to the total phenolic content of the whole nut.

Identification and Characterization of Phenolic Compounds in Black Walnut Kernels

Black walnuts ( Juglans nigra L.) are highly valued for producing phenolic-enriched nuts. The objectives of this study were to identify and characterize the phenolic contents of 11 different black walnut cultivars and compare the levels of these phenolics between black walnuts and English walnut ( Juglans regia L.). Totally, 16 phenolics including phenolic acids, flavonoids, and catechins were identified in the black walnut kernels, with ellagic acid predominating over the other phenolics. Significant differences were noted for the levels of quinic acid, gallic acid, 1,3,6-trigalloylglucose, catechin, and penta- O-galloyl-β-d-glucose between the studied black walnuts and English walnut. Through principal component analysis, 51.54% of the variance in the phenolic data was explained. The hierarchical cluster analysis results showed three groups to which each walnut sample belongs. Most of the phenolics identified in this study have been reported to exert potential health-promoting activities. The findings of this study will provide critical information for consumers, nutritional therapy practitioners, researchers, and producers.

The effect of heat treatment on phenolic compounds and fatty acid composition of Brazilian nut and hazelnut

Brazilian peanut oil content increased with oven heating (65.08%) and decreased with microwave heating process (61.00%). While the phenolic content of untreated Brazilian nut was the highest of 68.97 mg GAE/100 g. Hazelnut (Sivri) contained the highest antioxidant activity (86.52%, untreated). Results reflected significantly differences between the antioxidant effect and total phenol contents of Brazilian nut and hazelnut (Sivri) kernels heated in the oven and microwave. Microwave heating caused a decrease in antioxidant activity of hazelnut. Gallic acid, 3,4-dihydroxybenzoic acid and (+)- and catechin were the main phenolic compounds of raw Brazilian nut with the value of 5.33, 4.33 and 4.88 mg/100 g, respectively, while the dominant phenolics of raw hazelnut (Sivri) kernels were gallic acid (4.81 mg/100 g), 3,4-dihydroxybenzoic acid (4.61 mg/100 g), (+)-catechin (6.96 mg/100 g) and 1,2-dihydroxybenzene (4.14 mg/100 g). Both conventional and microwave heating caused minor reduction in phenolic compounds. The main fatty acids of Brazilian nut oil were linoleic (44.39-48.18%), oleic (27.74-31.74%), palmitic (13.09-13.70%) and stearic (8.20-8.91%) acids, while the dominant fatty acids of hazelnut (Sivri) oil were oleic acid (80.84%), respectively. The heating process caused noticeable change in fatty acid compositions of both nut oils.

Antioxidant properties and UPLC-MS/MS profiling of phenolics in jacquemont's hazelnut kernels (Corylus jacquemontii) and its byproducts from western Himalaya

A rapid and selective analytical method was developed to simultaneously quantify seven polyphenolic compounds (gallic acid, catechin, epicatechin, quercetin, kaempferol, syringic acid and p-coumaric acid). 15 phenolics of diverse groups in 80 % ethanolic extracts of jacquemont's hazelnut (Corylus jacquemontii) kernels and its byproducts from western Himalaya using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) were identified. The developed analytical method showed excellent linearity, repeatability and accuracy. Total phenols concentrations were found to be 4446, 1199 and 105 mg gallic acid equivalent (GAE)/Kg of dried extract for jacquemont's hazelnut skin, hard shell and kernels respectively. Antioxidant potential of defatted, raw jacquemont's hazelnut skin, hard shell and kernel extracts assessed by 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 2,2'-diphenyl-1-picrylhydrazyl (DPPH) methods were increased in a dose-dependent manner. The IC₅₀ values were observed as 23.12, 51.32, 136.46 and 45.73, 63.65, 169.30 μg/ml for jacquemont's hazelnut skin, hard shell, kernels by DPPH and ABTS assays, respectively. The high phenolic contents in jacquemont's hazelnut skin contributed towards their free radical scavenging capacities.