Comprehensive identification of walnut polyphenols by liquid chromatography coupled to linear ion trap-Orbitrap mass spectrometry

Epidemiologic studies and clinical trials have demonstrated consistent benefits of walnut consumption on coronary heart disease risk and other chronic diseases. Walnuts (Juglans regia L.) have been described previously as a rich source of polyphenols with a broad array of different structures. However, an accurate screening of its complete phenolic profile is still lacking. In the present work, liquid chromatography coupled with electrospray ionization hybrid linear trap quadrupole-Orbitrap mass spectrometry (LC-LTQ-Orbitrap) was applied for a comprehensive identification of phenolic compounds in walnuts. A total of 120 compounds, including hydrolysable and condensed tannins, flavonoids and phenolic acids were identified or tentatively identified on the base of their retention times, accurate mass measurements and subsequent mass fragmentation data, or by comparing with reference substances and literature. The peak area of each signal in mass chromatograms was used to provide semiquantitative information for comparison purposes. The most abundant ions were observed for ellagitannins, ellagic acid and its derivatives. Furthermore, the high-resolution MS analysis revealed the presence of eight polyphenols that have never been reported in walnuts: stenophyllanin C, malabathrin A, eucalbanin A, cornusiin B, heterophylliin E, pterocarinin B, reginin A and alienanin B.

Content of carotenoids, tocopherols, sterols, triterpenic and aliphatic alcohols, and volatile compounds in six walnuts (Juglans regia L.) varieties

The aim of this work was to study the content of tocopherols, sterols, triterpenic and aliphatic alcohols, carotenoids, and volatile compounds in the kernel oils from six walnut (Juglans regia L.) varieties. The levels of β-carotene ranged between 0.22 and 0.62 mg/kg, followed by lutein (0.01-0.06 mg/kg). The total content of tocopherol ranged from 186.5 to 436.2 mg/kg of the extracted oil and the major isoform in all samples was γ-tocopherol. The most abundant phytosterol was β-sitosterol (974-1494 mg/kg) followed by campesterol then Δ-5-avenasterol. The major triterpenic alcohol was cycloartenol (226.4-532.1 mg/kg). Hexacosanol (9.71-28.15 mg/kg) was the major aliphatic alcohol. The detected volatile compounds were pentanal, hexanal, nonanal, 2-decenal and hexanol. The statistical analysis showed significant differences between varieties, which are probably due to genetic factors.

Determination and characterization of kernel biochemical composition and functional compounds of Persian walnut oil

Kernel chemical composition and fatty acids profile of three walnut cultivars (Toyserkan, Chaboksar and Karaj) was analyzed. Some physicochemical properties, total phenolics content (TPC), ortho-diphenols content (ODC) and total tocopherol concentration (TTC) of extracted oils from the walnuts were also determined. The antioxidant activity of oil was measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and β-carotene bleaching assays. The analysis of chemical composition revealed that protein and dietary fiber was highest in Toyserkan cultivar. Phosphorus was the most abundant element in the walnut kernels, followed by potassium, magnesium and calcium. The linoleic acid and linolenic contents ranged from 50.15% to 51.36% and 10.48% to 12.04%, respectively. Also, the results demonstrated that acid value, saponification value and viscosity of extracted oil had significantly varied between all cultivars. The extracted oil from Chaboksar cultivar illustrated more hydro peroxides and secondary products than those obtained from other cultivars. A positive correlation was found between Rancimat values and oleic acid content (r = 0.60), but considerably negative correlation with TTC (r = -0.81) and TPC (r = -0.92). The relationship between percentage of remaining DPPH radical and β-carotene of walnut oils showed high correlation among three selected cultivars (r = -0.94 to -0.97).

Identification and quantification of the major phenolic constituents in Juglans regia L. peeled kernels and pellicles, using HPLC-MS/MS

This study was designed to identify and quantify the major phenolic constituents in peeled kernel and pellicle of the walnut Juglans regia L. Data were compared across six different cultivars: 'Fernor', 'Fernette', 'Franquette', 'Sava', 'Krka' and 'Rubina'. High-performance liquid chromatography coupled with mass spectrometry was used to identify and quantify these compounds. Nineteen ellagitanins, 12 ellagic acid derivatives, 4 anthocyanins and 5 other phenols were identified in the pellicle of these walnuts, and 15 dicarboxylic acid derivatives and 1 phenol in the peeled walnut kernels. Thirteen previously unreported compounds were identified in the peeled walnut kernels, and 14 in the walnut pellicle. Hydrolysable tannins were the main phenolic compounds identified in the walnut kernels, and accounted for 31.0% to 35.1% of the total phenolics analysed. The highest intake of total phenolics content per walnut kernel can be obtained by consumption of 'Franquette' and 'Rubina', with the lowest for 'Krka'.

Cavitation and water fluxes driven by ice water potential in Juglans regia during freeze-thaw cycles

Freeze-thaw cycles induce major hydraulic changes due to liquid-to-ice transition within tree stems. The very low water potential at the ice-liquid interface is crucial as it may cause lysis of living cells as well as water fluxes and embolism in sap conduits, which impacts whole tree-water relations. We investigated water fluxes induced by ice formation during freeze-thaw cycles in Juglans regia L. stems using four non-invasive and complementary approaches: a microdendrometer, magnetic resonance imaging, X-ray microtomography, and ultrasonic acoustic emissions analysis. When the temperature dropped, ice nucleation occurred, probably in the cambium or pith areas, inducing high water potential gradients within the stem. The water was therefore redistributed within the stem toward the ice front. We could thus observe dehydration of the bark's living cells leading to drastic shrinkage of this tissue, as well as high tension within wood conduits reaching the cavitation threshold in sap vessels. Ultrasonic emissions, which were strictly emitted only during freezing, indicated cavitation events (i.e. bubble formation) following ice formation in the xylem sap. However, embolism formation (i.e. bubble expansion) in stems was observed only on thawing via X-ray microtomography for the first time on the same sample. Ultrasonic emissions were detected during freezing and were not directly related to embolism formation. These results provide new insights into the complex process and dynamics of water movements and ice formation during freeze-thaw cycles in tree stems.

Association and linkage mapping to unravel genetic architecture of phenological traits and lateral bearing in Persian walnut (Juglans regia L.)

BACKGROUND

Unravelling the genetic architecture of agronomic traits in walnut such as budbreak date and bearing habit, is crucial for climate change adaptation and yield improvement. A Genome-Wide Association Study (GWAS) using multi-locus models was conducted in a panel of 170 walnut accessions genotyped using the Axiom™ J. regia 700 K SNP array, with phenological data from 2018, 2019 and legacy data. These accessions come from the INRAE walnut germplasm collection which is the result of important prospecting work performed in many countries around the world. In parallel, an F1 progeny of 78 individuals segregating for phenology-related traits, was genotyped with the same array and phenotyped for the same traits, to construct linkage maps and perform Quantitative Trait Loci (QTLs) detection.

RESULTS

Using GWAS, we found strong associations of SNPs located at the beginning of chromosome 1 with both budbreak and female flowering dates. These findings were supported by QTLs detected in the same genomic region. Highly significant associated SNPs were also detected using GWAS for heterodichogamy and lateral bearing habit, both on chromosome 11. We developed a Kompetitive Allele Specific PCR (KASP) marker for budbreak date in walnut, and validated it using plant material from the Walnut Improvement Program of the University of California, Davis, demonstrating its effectiveness for marker-assisted selection in Persian walnut. We found several candidate genes involved in flowering events in walnut, including a gene related to heterodichogamy encoding a sugar catabolism enzyme and a cell division related gene linked to female flowering date.

CONCLUSIONS

This study enhances knowledge of the genetic architecture of important agronomic traits related to male and female flowering processes and lateral bearing in walnut. The new marker available for budbreak date, one of the most important traits for good fruiting, will facilitate the selection and development of new walnut cultivars suitable for specific climates.

Antibacterial and anti-biofilm activities of walnut pellicle extract (Juglans regia L.) against coagulase-negative staphylococci

Juglans regia L. (common walnut) is a deciduous tree belonging to Juglandaceae family. Since ancient time, walnut was widely used in traditional medicine for its antioxidant, antidiabetic, antimicrobial, anti-inflammatory, anti-atherogenic and liver-protective effects. In this work, the antibacterial and anti-biofilm activities of walnuts pellicle extract against coagulase-negative staphylococci were evaluated. Qualitative chemical analysis was performed by the thin layer chromatography. UPLC-Ms/Ms was used to identify the chemical composition of J. regia extract. The total flavonoid and phenolic contents were determined by the Aluminium chloride and Folin-Ciocalteu methods, respectively. The extract showed antibacterial activity with MIC ranging from 3.60 to 461.75 µg/ml and MBC ranging from 461.75 to >461.75 µg/ml. Furthermore, it significantly reduced biofilm biomass and cell viability in a dose-dependent manner. Biological activities of J. regia extract may be due to its high flavonoid and phenolic contents. The obtained results are promising and they deserve further scientific investigations.

Serendipita indica alleviates drought stress responses in walnut (Juglans regia L.) seedlings by stimulating osmotic adjustment and antioxidant defense system

Juglans regia L. is a good host for Serendipita indica. Under drought condition, seedlings colonized with S. indica showed higher values in plant height, total fresh biomass, root/shoot ratio, relative growth rate, leaf relative water content and chlorophyll content, gas exchange parameters, maximal photochemical efficiency, photochemical quenching, and effective photosystem II quantum yield than the uncolonized seedlings. It suggested beneficial effects of S. indica on host plants' growth and physiological parameters in response to drought. In comparison with the uncolonized seedlings, S. indica-colonized seedlings showed lower levels in hydrogen peroxide, superoxide anion, malondialdehyde, and relative electrical conductivity under drought condition, suggesting the ability of S. indica to prevent or retard the accumulation of reactive oxygen species and to diminish the oxidative injure. Furthermore, walnut seedlings responded to drought by actively accumulating osmotic regulation substances including soluble protein, soluble sugar, and proline. Root colonization with S. indica was more conductive to the accumulation. Moreover, in response to drought stress, walnut seedlings, regardless of colonization, increased activities of superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, and glutathione reductase, levels of ascorbate and glutathione, and ratios of reduced ascorbate/dehydroascorbic acid and reduced glutathione/oxidized glutathione in leaves and roots. S. indica colonization induced much more increase in the abovementioned indicators as compared to the uncolonized seedlings. Overall, S. indica colonization alleviated the detrimental effects of drought stress by altering root system, enhancing osmotic adjustment, and repressing the accumulation of reactive oxygen species via stimulating antioxidant system including enzymatic and nonenzymatic components. KEY POINTS: • S. indica stimulated root growth of walnut seedlings under drought condition. • S. indica accelerated osmotic adjustment under drought condition. • S. indica activated antioxidant defense mechanism under drought condition.

Prediction of the antimicrobial activity of walnut (Juglans regia L.) kernel aqueous extracts using artificial neural network and multiple linear regression

The mathematical model was established to determine the diameter of inhibition zone of the walnut extract on the twelve bacterial species. Type of extraction, concentration, and pathogens were taken as input variables. Two models were used with the aim of designing this system. One of them was developed with artificial neural networks (ANN), and the other was formed with multiple linear regression (MLR). Four common training algorithms were used. Levenberg-Marquardt (LM), Bayesian regulation (BR), scaled conjugate gradient (SCG) and resilient back propagation (RP) were investigated, and the algorithms were compared. Root mean squared error and correlation coefficient were evaluated as performance criteria. When these criteria were analyzed, ANN showed high prediction performance, while MLR showed low prediction performance. As a result, it is seen that when the different input values are provided to the system developed with ANN, the most accurate inhibition zone (IZ) estimates were obtained. The results of this study could offer new perspectives, particularly in the field of microbiology, because these could be applied to other type of extraction, concentrations, and pathogens, without resorting to experiments.

Protective Effect of Juglans regia L. Walnut Extract Against Oxidative DNA Damage

Walnuts (Juglans regia L.) are relevant components of the Mediterranean diet providing important macronutrients, micronutrients and other bioactive constituents including unsaturated fatty acids, proteins, fiber, vitamins, minerals, phytosterols and polyphenols. Although the walnut beneficial effects in human health are widely recognized by a lot of epidemiologic studies very little is known regarding its effect on damaged DNA. The aim of the present study was to investigate the effect of Juglans regia L. ethanolic extract from kernel on the induction of DNA strand breaks by thiol/Fe³⁺/O₂ mixed function oxidase, tert-butyl hydroperoxide or UVC radiations in acellular and cellular models. Plasmid DNA cleavage and fast Halo assay were used to monitor oxidative damage to DNA. Both approaches showed protection of oxidatively injured DNA. These results agree with a lot of scientific proofs which recommend walnut as dietary adjunct in health promotion and prevention as well as in treatment of lifestyle-related oxidative diseases.

Effect of genotype and crop year on the nutritional value of walnut virgin oil and defatted flour

The present study analyses the health-promoting compounds of walnut oil and walnut defatted flour obtained using hydraulic pressing. To identify the cultivar effect, nine walnut varieties were harvested in the same plot for two years to control environmental and agricultural management effects on kernel chemical traits. Beyond the variability reported in the products obtained from the different cultivars analysed, the crop year showed a crucial effect in the nutritional value of walnut products. Specifically, the variability caused for the crop year in the concentration of oleic and linoleic acids, phytosterols, polyphenols, tocopherols, proteins and essential minerals (K, Mg, P, S, Cu, Fe, Mn, Mo, Ni) was greater that the reported for the genotype. These findings suggest that the nutritional value of walnut oil and walnut flour depends on the crop season largely than expected, even when average annual weather conditions are similar. As a result, focus must change in the study of cultivar effect on walnut products to a wider analysis of specific variables related to crop year conditions.

Determination of the Geographical Origin of Walnuts (Juglans regia L.) Using Near-Infrared Spectroscopy and Chemometrics

The prices of walnuts vary according to their geographical origin and, therefore, offer a financial incentive for adulteration. A reliable analysis method is required to quickly detect possible misdeclarations and thus prevent food fraud. In this study, a method to distinguish between seven geographical origins of walnuts using Fourier transform near-infrared (FT-NIR) spectroscopy combined with chemometrics as a fast, versatile, and easy to handle analytical tool was developed. NIR spectra of 212 ground and afterwards freeze-dried walnut samples, harvested in three consecutive years (2017-2019), were collected. We optimized the data pre-processing by applying and evaluating 50,545 different pre-processing combinations, followed by linear discriminant analysis (LDA) which was confirmed by nested cross-validation. The results show that in the scope of our research minimal pre-processing led to the best results: By applying just multiplicative scatter correction (MSC) and median centering, a classification accuracy of 77.00% ± 1.60% was achieved. Consequently, this complex model can be used to answer economically relevant questions e.g., to distinguish between European and Chinese walnuts. Furthermore, the great influence of the applied pre-processing methods, e.g., the selected wavenumber range, on the achieved classification accuracy is shown which underlines the importance of optimization of the pre-processing strategy.

HS-SPME GC-MS characterization of volatiles in processed walnuts and their oxidative stability

Processed walnuts including hot air-dried and roasted walnuts were prepared. Volatiles in raw and processed walnuts were analyzed using head-space solid phase microextraction combined with gas chromatography and mass spectrometry. Oxidative stability of hot air-dried walnuts in different antioxidants, with or without vacuum package was studied to find a proper package for oxidation stability of hot air-dried walnuts. The results showed that there were 14 volatiles in raw walnuts, 28 in hot air-dried walnuts and 38 in roasted walnuts. The changes of oil quality indices, total phenols, malondialdehyde and free radical scavenging activities during storage at 60 °C showed that the oil oxidation increased with storage time. The addition of antioxidants and vacuum package could slow down the oxidation. Vacuum aluminum foil package (14 × 20 cm) can delay the oil oxidation and extend the shelf life to ~ 230 days of hot air-dried walnuts at 20 °C. With added antioxidant this was extended to ~ 257 days.

Genome-Wide Association Study Reveals Candidate Genes Involved in Fruit Trait Variation in Persian Walnut (Juglans regia L.)

Elucidating the genetic determinants of fruit quality traits in walnut is essential to breed new cultivars meeting the producers and consumers' needs. We conducted a genome-wide association study (GWAS) using multi-locus models in a panel of 170 accessions of Juglans regia from the INRAE walnut germplasm collection, previously genotyped using the Axiom^TM J. regia 700K SNP array. We phenotyped the panel for 25 fruit traits related to morphometrics, shape, volume, weight, ease of cracking, and nutritional composition. We found more than 60 marker-trait associations (MTAs), including a highly significant SNP associated with nut face diameter, nut volume and kernel volume on chromosome 14, and 5 additional associations were detected for walnut weight. We proposed several candidate genes involved in nut characteristics, such as a gene coding for a beta-galactosidase linked to several size-related traits and known to be involved in fruit development in other species. We also confirmed associations on chromosomes 5 and 11 with nut suture strength, recently reported by the University of California, Davis. Our results enhance knowledge of the genetic control of important agronomic traits related to fruit quality in walnut, and pave the way for the development of molecular markers for future assisted selection.

Amelioration of cognitive deficit in zebrafish by an undescribed anthraquinone from Juglans regia L.: An in-silico, in-vitro and in-vivo approach

An undescribed anthraquinone assigned as 1-Hydroxy-5,5-dimethyl-5,6,7,8-tetrahydro-9,10-anthraquinone (compound 1) was isolated from ethylacetate extract of Juglans regia L. The structure of the compound was established on the basis of 1D, 2D NMR (HSQC, HMBC, COSY), ESI-QTOF-MS/MS spectroscopy. The molecular docking studies of compound 1 indicated similar molecular interactions as that of co-crystalized inhibitor. Compound 1 showed hydrogen bonds with residues PHE295, GLY121, π-σ interactions with TYR 341, π-π interactions with HIS 447 residues, and π-alkyl with TRP86 and TYR 337. On the basis of in-silico interaction studies of compound 1 with proteins, it was tested using acetylcholinesterase inhibition assay, acrylamide-induced neurotoxicity test of zebrafish larva, and scopolamine-induced cognitive deficit model of adult zebrafish. The compound 1 showed potent acetylcholinesterase inhibition activity, prevented acrylamide-induced neurotoxicity and improved learning and memory functions in T-maze test. The results established compound 1 to be a potential neuroprotective natural product for amelioration of cognitive impairment.

Developmental role of phenylalanine-ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H) genes during adventitious rooting of Juglans regia L. microshoots

Phenylalanine-ammonia-lyase and cinnamate-4-hydroxylase play important role in the phenylpropanoid pathway, which produces many biologically important secondary metabolites participating in normal plant development. Flavonol quercetin is the main representant of these compounds that has been identified in numerous Juglans spp. In this survey, the developmental expression patterns of PAL and C4H genes during in vitro rooting of two walnut cultivars 'Sunland' and 'Howard' was examined by RT-PCR. To understand the potential role in rooting, the changing pattern of endogenous content of quercetin was also analyzed by HPLC. The 'Sunland' with better capacity to root had more quercetin content during the "inductive phase" of rooting than 'Howard'. In each cultivar, the level of PAL transcripts showed the same behavior with the changing patterns of quercetin during root formation of microshoots. The positive correlation between the changes of quercetin and PAL-mRNA indicated that PAL gene may have an immediate effect on flavonoid pathway metabolites including quercetin. Although the behavioral change of C4H expression was similar in both cultivars during root formation (with significantly more level for 'Howard'), it was not coincide with the changes of quercerin concentrations. Our results showed that C4H function is important for the normal development, but its transcriptional regulation does not correlate with quercetin as an efficient phenolic compound for walnut rhizogenesis.

Improving walnuts' preservation by using walnut phenolic extracts as natural antioxidants through a walnut protein-based edible coating

Walnut kernels contain high amounts of polyunsaturated fatty acids that determine a limited shelf life on these nuts. The application of walnut phenolics as antioxidants through a walnut protein-based coating, obtained from walnut oil cake residue, can help to increase the shelf life of walnuts. The objective was to evaluate the preservative effect of walnut polyphenols included in a walnut-proteic edible coating on walnut kernels. Three treatments of walnuts coated with walnut flour were prepared: without the addition of antioxidants (control); with the addition of a walnut phenolic extract; and with the addition of butylated hydroxytoluene (BHT). On the last storage day, the sample with the addition of walnut phenolics presented a lower peroxide (3.64 meq 0₂ /kg oil) and anisidine value (1.11), conjugated diene (15.92), and hexanal content (19.67 × 10⁶ e.c.) than the control sample (6.23, 1.81, 24.65, and 122.37 × 10⁶ e.c., respectively). Also, on the last day, the control sample showed the highest deterioration of polyunsaturated fatty acids (from 74.83 to 71.08 g/100g), carotenoid (from 3.43 to 1.90 mg/kg), and γ-tocopherol content (from 349.66 to 298.42 mg/kg). In addition, this sample exhibited the highest oxidized (20.33) and the lowest walnut flavor intensity (64.67) on day 84. Regarding consumer acceptance, the phenolic-added sample displayed a greater flavor acceptance score. Walnut phenolics, implemented through a walnut protein-based coating, improve the preservation of walnuts. PRACTICAL APPLICATION: The combination of walnut-phenolic extracts and walnut-based edible coating applied on walnuts by food industries allows to prolong their shelf life, by preserving their nutritional, sensory, and quality properties. Considering the practical feasibility, the procedure used to prepare these products is simple and requires machineries already present in food industries. In addition, the utilization of this coating with walnut-phenolics exerts benefits like, the prevention of allergen cross-contamination in the chain of production, the utilization of an industry's residue, the replacement of synthetic antioxidants and, and the diminishment of the amount and thickness of plastic needed for walnuts' packaging.

Influence of epiphytic micro-organisms on leaf wettability: wetting of the upper leaf surface of Juglans regia and of model surfaces in relation to colonization by micro-organisms

Wetting of the upper leaf surface of Juglans regia L. and of model surfaces colonized by epiphytic micro-organisms was investigated by measuring contact angles of aqueous solutions buffered at different pH values. During June to October 1995, contact angles of aqueous solutions on the leaf surface of J. regia decreased by angles ranging from 12° (low pH values) to 25° at high pH values. At the end of this vegetation period, wetting was strongly dependent on pH showing significantly lower contact angles with alkaline solutions (pH 9·0) than with acidic solutions (pH 3·0). Contact angle titration measured angles on the leaf surface as a function of the pH of buffered aqueous solutions, covering a pH range from 3·0 to 11·0. Titration curves revealed inflection points around 7·5, indicating the existence of ionizable carboxylic groups at the interface of the phylloplane. Altered leaf-surface wetting properties observed on the intact leaf surface could be simulated in model experiments by measuring contact angles on artificial surfaces colonized by Pseudomonas fluorescens and by epiphytic micro-organisms isolated from the phylloplane of J. regia. Strong evidence is provided that interfacial carboxylic groups derive from epiphytic micro-organisms present on the phylloplane. Results suggest that the age-dependent increase in, and pH dependence of, wetting as leaves mature are related to the presence of epiphytic micro-organisms on the phylloplane. Ecological consequences of increased leaf-surface wetting, concerning the structure of the leaf surface as a microhabitat for epiphytic micro-organisms, are discussed.

Juglans regia L. protects against UVB induced apoptosis in human epidermal keratinocytes

The present study was aimed to investigate the photoprotective effect of the male flower of J. regia L. (MEJR) against ultraviolet-B induced apoptosis in human skin cells. Human skin epidermal keratinocytes were pretreated with the MEJR (80 µg/ml, has been selected after MTT assay), prior to 30 min UVB-irradiation at a dose of 20 mJ/cm². Mitochondrial membrane potential was evaluated using Rhodamine-123 staining; the % apoptosis by Hoechst staining and acridine orange staining; DNA damage was measured by comet assay. The levels of p53, Bax, Bcl-xL, Bcl-2, Cytochrome c, Caspase-9 and Caspase-3 expression in HaCaT cells were analyzed by western blotting and RT-PCR. Pretreatment with MEJR 80 µg/ml prior to UVB-irradiation significantly prevents apoptotic characteristics, DNA damage and loss of mitochondrial membrane potential. Thus, MEJR protects UVB-mediated human skin cells, by modulating the expression of apoptotic markers and UVB-induced DNA damage in HaCaT cells.

Chemical Composition and the Effect of Walnut Hydrosol on Glycemic Control of Patients With Type 1 Diabetes

BACKGROUND

Walnut hydrosol (WH) is used extensively by Iranian people with diabetes in order to control blood sugar (BS). There are few data regarding the effect of walnut on controlling diabetes.

OBJECTIVES

A pilot study to determine the efficacy and safety of WH in patients with type 1 diabetes.

MATERIALS AND METHODS

Eight patients with diabetes mellitus (DM) type 1 were enrolled in the study. They did not use any medicine except insulin. They were advised to drink 250 mL WH after meals twice a day for four weeks. Their BS level was measured and their insulin dose was changed according to their BS. After four weeks, they discontinued WH use and their BS level was checked for two weeks. Descriptive statistics was used to analyze the data. Also, the essential oil of the sample was extracted using a liquid extractor and then analysis of the constituents was performed.

RESULTS

The average daily BS level and insulin dose decreased in seven subjects. Two subjects developed generalized pruritic erythematous skin rash. One patient presented hypoglycemic coma. She had no other coma risk factor. Seven compounds were identified in the walnut essential oil and the rate of monoterpenoid and sesquiterpenes hydrocarbons were 53.45% and 5.95%, respectively. The main constituents of the oil were carvacrol (33.21%), thymol (16%) and homoveratrole (15.83%).

CONCLUSIONS

WH may control the glycemic level in people with diabetes, but it may be associated with minor and major side effects. Further in vitro studies, using these seven compounds, are recommended to determine the efficacy and complications of WH in people with diabetes.

F. R. Ferreira I, Ferreira O. Insights on the Extraction Performance of Alkanediols and Glycerol: Using Juglans regia L. Leaves as a Source of Bioactive Compounds

Glycerol and alkanediols are being studied as alternative solvents to extract phytochemicals from plant material, often as hydrogen bond donors in deep eutectic solvents (DESs). Many of those alcohols are liquid at room temperature, yet studies of their use as extraction solvents are scarce. In this work, glycerol and a series of alkanediols (1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, and 1,2-hexanediol) were studied for the extraction of phenolic compounds from Juglans regia L. leaves, a rich source of this class of bioactive compounds. The extraction yield was quantified, and the bioactivity of both extracts and pure solvents was evaluated by measuring the anti-inflammatory and cytotoxic activities. The solvents showing the best combined results were 1,2 and 1,3-propanediol, as their extracts presented a high amount of phenolic compounds, close to the results of ethanol, and similar cytotoxicity against cervical carcinoma cells, with no impact on non-tumor porcine liver cells in the studied concentration range. On the other hand, none of the extracts (and solvents) presented anti-inflammatory activity. Overall, the results obtained in this work contribute to the study of alternative solvents that could potentially be used also as formulation media, highlighting the importance of walnut leaves as a source of bioactive compounds.

Comparative Investigation of Chemical Constituents of Kernels, Leaves, Husk, and Bark of Juglans regia L., Using HPLC-DAD-ESI-MS/MS Analysis and Evaluation of Their Antioxidant, Antidiabetic, and Anti-Inflammatory Activities

Leaves, husk, kernels, and bark methanolic extracts of Juglans regia L. were tested for their in vitro antidiabetic, anti-inflammatory, and antioxidant activities. For these purposes, α-amylase and α-glucosidase were used as the main enzymes to evaluate antidiabetic activities. Moreover, lipoxidase and tyrosinase activities were tested to estimate anti-inflammatory properties. Antioxidant properties of Juglans regia L., extracts were determined using three different assays. Leaves extract has an important radical scavenging activity and a-amylase inhibition. Similarly, husk extracts showed high total phenolic content (306.36 ± 4.74 mg gallic acid equivalent/g dry extract) with an important α-amylase inhibition (IC50 = 75.42 ± 0.99 µg/mL). Kernels exhibit significant tyrosinase (IC50 = 51.38 ± 0.81 µg/mL) correlated with antioxidant activities (p < 0.05). Husk and bark extracts also showed strong anti-lipoxidase activities with IC50 equal to 29.48 ± 0.28 and 28.58 ± 0.35 µg/mL, respectively. HPLC-DAD-ESI-MS/MS analysis highlights the phenolic profile of methanolic extracts of Juglans regia L. plant parts. The identified polyphenols were known for their antioxidant, antidiabetic (dicaffeoyl-quinic acid glycoside in kernels), and anti-inflammatory (3,4-dihydroxybenzoic acid in leaves) activities. Further investigations are needed to determine molecular mechanisms involved in these effects as well as to study the properties of the main identified compounds.

The double effect of walnut septum extract (Juglans regia L.) counteracts A172 glioblastoma cell survival and bacterial growth

Walnut (Juglans regia L.) is considered to be a 'superfood' for its multiple protective actions on human health. Walnut extracts have proven antitumor activity in different cancer cell lines. However, the efficacy of septum extract against glioblastoma has still not been investigated. Glioblastoma is the most difficult type of brain cancer to treat. The standard therapy, based on temozolomide, causes several side effects, including neutropenia and lymphocytopenia, which often favor the onset of opportunistic infections. In the present study, the chemical profile of the Sicilian walnut septum ethanolic extract was analyzed using high-performance liquid chromatography (HPLC)-diode array detection and HPLC-electrospray ionization tandem mass spectrometry. The potential cytostatic activity of the extract against the human A172 glioblastoma cell line was investigated and the results showed that the extract could decrease cancer cell proliferation and migration. Using cytofluorimetric analyses and caspase-3 assays, the pro-apoptotic action of walnut extract was demonstrated. Furthermore, the evaluation of the antibacterial activity high-lighted the efficacy of the extract in reducing Gram-positive and Gram-negative bacterial growth, most of which were resistant to the antibiotic, ciprofloxacin. Finally, Prediction of Activity Spectra for Substances analysis showed the predicted antitumor and antibacterial activity of HPLC detected compounds. The promising results could provide novel perspective in the field of chemotherapeutic co-adjuvants.

Genome-Wide Identification, Classification, Expression and Duplication Analysis of bZIP Family Genes in Juglans regia L

Basic leucine zipper (bZIP), a conserved transcription factor widely found in eukaryotes, has important regulatory roles in plant growth. To understand the information related to the bZIP gene family in walnut, 88 JrbZIP genes were identified at the genome-wide level and classified into 13 subfamilies (A, B, C, D, E, F, G, H, I, J, K, M, and S) using a bioinformatic approach. The number of exons in JrbZIPs ranged from 1 to 12, the number of amino acids in JrbZIP proteins ranged from 145 to 783, and the isoelectric point ranged from 4.85 to 10.05. The majority of JrbZIP genes were localized in the nucleus. The promoter prediction results indicated that the walnut bZIP gene contains a large number of light-responsive and jasmonate-responsive action elements. The 88 JrbZIP genes were involved in DNA binding and nucleus and RNA biosynthetic processes of three ontological categories, molecular functions, cellular components and biological processes. The codon preference analysis showed that the bZIP gene family has a stronger bias for AGA, AGG, UUG, GCU, GUU, and UCU than other codons. Moreover, the transcriptomic data showed that JrbZIP genes might play an important role in floral bud differentiation. The results of a protein interaction network map and kegg enrichment analysis indicated that bZIP genes were mainly involved in phytohormone signaling, anthocyanin synthesis and flowering regulation. qRT-PCR demonstrated the role of the bZIP gene family in floral bud differentiation. Co-expression network maps were constructed for 29 walnut bZIP genes and 6 flowering genes, and JrCO (a homolog of AtCO) was significantly correlated (p < 0.05) with 13 JrbZIP genes in the level of floral bud differentiation expression, including JrbZIP31 (homolog of AtFD), and JrLFY was significantly and positively correlated with JrbZIP10,11,51,59,67 (p < 0.05), and the above results suggest that bZIP family genes may act together with flowering genes to regulate flower bud differentiation in walnut. This study was the first genome-wide report of the walnut bZIP gene family, which could improve our understanding of walnut bZIP proteins and provide a solid foundation for future cloning and functional analyses of this gene family.

Phytochemical Study of Juglans regia L. Pericarps from Greece with a Chemotaxonomic Approach

Phytochemical research of different polarity extracts from green Juglans regia L. pericarps from Greece afforded 32 compounds: four pentacyclic triterpenes (1 - 4), three sesquiterpenes (5 - 7), four tetralones (8 - 11), two naphthoquinones (12 and 13), seven phenolic acids (14 - 20), one diarylheptanoid (21), one neo-lignan (22), seven flavonoids (23 - 29), two phenylethanoids (30 and 31) and one hydrolysed tannin (32). Compounds 4 and 29 are isolated for the first time from the species, while compounds 3, 7, 20, 22, 23, 24, 25, 26, 28, 30 are reported for the first time in Juglandaceae. Chemotaxonomic significance of isolated compounds into Junglandaceae family is thoroughly discussed.