Identification of Key Antioxidants of Free, Esterified, and Bound Phenolics in Walnut Kernel and Skin.

Walnut is a natural source of antioxidants. Its antioxidant capacity is determined by the distribution and composition of phenolics. The key phenolic antioxidants in various forms (free, esterified, and bound) in walnut kernel (particularly seed skin) are unknown. The phenolic compounds in twelve walnut cultivars were analyzed using ultra-performance liquid chromatography coupled with a triple quadrupole mass spectrometer in this study. A boosted regression tree analysis was used to identify the key antioxidants. Ellagic acid, gallic acid, catechin, ferulic acid, and epicatechin were abundant in the kernel and skin. The majority of phenolic acids were widely distributed in the free, esterified, and bound forms in the kernel but more concentrated in bound phenolics in the skin. The total phenolic levels of the three forms were positively correlated with antioxidant activities (R = 0.76-0.94, p < 0.05). Ellagic acid was the most important antioxidant in the kernel, accounting for more than 20%, 40%, and 15% of antioxidants, respectively. Caffeic acid was responsible for up to 25% of free phenolics and 40% of esterified phenolics in the skin. The differences in the antioxidant activity between the cultivars were explained by the total phenolics and key antioxidants. The identification of key antioxidants is critical for new walnut industrial applications and functional food design in food chemistry.

Characterization of iron walnut in different regions of China based on phytochemical composition.

Little is known about the phytochemical composition of iron walnuts. Differences in the geographical origin of iron walnuts associated with economic benefits should also be examined. In this study, the phytochemical composition (fatty acids, Vitamin E, total polyphenols and flavonoids, amino acids, and minerals) of iron walnuts in China was investigated. The results showed that there were significant differences (p < 0.05) in the phytochemical composition of iron walnut oils and flours from different regions. Positive (r > 0.5, p < 0.05) and negative (r < - 0.5, p < 0.05) correlations were found between amino acids/minerals and amino acids/oleic acid, with the highest correlation coefficient (r = 0.742, p < 0.05) between Cu and tyrosine. In addition, based on the 12 phytochemical fingerprints selected by random forest, a geographical-origin identification model for iron walnuts was established, with a corresponding correct classification rate of 96.6%. The top three phytochemical fingerprints for the geographical-origin identification of iron walnut were microelements, macroelements, and antioxidant composition, with contribution rates of 61.7%, 18.1%, and 9.9%, respectively.

Phenolic profiles and antioxidant activities of free, esterified and bound phenolic compounds in walnut kernel.

The free, esterified and bound forms of 37 phenolic compounds (including hydroxybenzoic acid, hydroxycinnamic acids, flavanols, flavonols and flavones) from walnut kernel (Juglans regia L.) were investigated in this study. Results showed that the majority of walnut phenolics were presented in the free form (51.1%-68.1%), followed by bound (21.0%-38.0%) and esterified forms (9.7%-18.7%). Ellagic acid, gallic acid, ferulic acid, sinapic acid and caffeic acid were widely distributed in three forms. Differently, jeuglone, kaempferol, quercetin-7-o-ß-d-glucoside and dihydroquercetin were only found in free phenolics. Among the three forms, free phenolics had the highest radical scavenging activity (IC50: DPPH, 15.5 µg/ml; ABTS, 13.6 µg/ml). The correlation coefficients between the antioxidant activities of phenolics and their corresponding contents were 0.82-0.92. More soluble phenolics (free and esterified forms) could be extracted by acetone, while methanol was better at extracting insoluble bound phenolics.

Evaluation of Polycyclic Aromatic Hydrocarbons (PAHs) in Bamboo Shoots from Soil.

The toxicity, carcinogenicity and persistence of polycyclic aromatic hydrocarbons (PAHs) pose a great threat to the ecological system and human health. The contamination levels, translocation and source analysis of 16 PAHs in bamboo shoot and its planted soil were investigated. The average concentrations of total PAHs were 18.80 ± 1.90 µg/kg and 123.98 ± 113.36 µg/kg in bamboo shoots and soils, respectively. The most abundant PAH was Phenanthrene (PHE), with the detected average concentrations of 5.85 µg/kg in bamboo shoots and 19.28 µg/kg in soils. The highest detected types of PAHs were 3 rings and 4 rings, with the proportions of 80.69% (bamboo shoots) and 35.23% (soils). The transfer factors of PAHs were ranged from 0.011 to 0.895, in which PAHs with 3 rings showed the strongest transfer ability. The combustion of biomass and petroleum might be the main source of PAHs in the planted soils of bamboo shoots.

Determination of benzo[a]pyrene in camellia oil via vortex-assisted extraction using the UPLC-FLD method.

In this paper, vortex-assisted extraction using the ultraperformance liquid chromatography analysis method was performed to determine benzo[a]pyrene in camellia oil. Optimum results were obtained when 0.5 g of oil sample was used followed by vortex-assisted extraction for 10 min with 25 mL of acetonitrile. Chromatographic separation was performed on an Agilent ZORBAX Eclipse Plus C18 column (2.1mm×100mm, particle size 1.8 µm). The optimum mobile phase comprised 70% acetone and 30% water. The detection limit of benzo[a]pyrene was 0.2 µg/kg. The recoveries were in the range of 81.0-97.0%. The proposed method was simple and fast, and it provided high throughput in the determination of benzo[a]pyrene in an oil matrix sample.

[Determination of 18 polychlorinated biphenyls in camellia seeds by multiple vortex and gas chromatography-triple quadrupole mass spectrometry].

A method based on the cleaning effects of different sorbents and gas chromatography-triple quadrupole mass spectrometry (GC-QQQ-MS/MS) was developed for the determination of 18 polychlorinated biphenyls (PCBs) in camellia seeds. The camellia seeds were extracted with acetonitrile, salted out with sodium chloride, then cleaned-up by QuEChERS with anhydrous MgSO4, C18, primary secondary amine (PSA), and multi walled carbon nanotubes (NANO) using multiple vortex after the centrifugal separation, and finally analyzed by GC-QQQ-MS/MS in multiple reaction monitoring mode via positive electrospray ionization. All the 18 PCBs could be completely separated with an excellent linear relationship. The limits of detection for the 18 PCBs were 5 µg/kg. For all the samples, the mean spiked recoveries was 109.2% with relative standard deviations (RSDs) of 2.9%-6.2% (n=3). The extraction, purification and analytical methods were developed and assessed. The method was successfully applied to the 48 samples from three main producing provinces of camellia seeds. All the 18 PCBs were not detected from the 48 samples.

The Fate of Organophosphorus Pesticides during Camellia Oil Production.

The purpose of this study was to investigate the fate of organophosphorus pesticides (OPs) during camellia oil production process, from camellia fruit to the final oil product. The results showed that the OPs were mainly distributed in the peel of camellia fruit, basically above 40% after the pesticide application of 7 d (P < 0.05). A small amount of OPs could enter into the seed and convert to crude camellia oil, with the concentration of 19.5 to 548.2 mg/L. In addition, metabolites of OPs (25.7 to 768.9 mg/L) could be detected in the crude camellia oil. Moreover, the refining process (degumming, deacidfying, bleaching) had a significant effect on the removal of OPs from the crude camellia oil (P < 0.05), and the effect was related to the octanol-water partition constant (LogP) of pesticide. The larger the LogP, the more stable the OPs were during refining process. The final refined camellia oil was found to have no detectable levels of OPs metabolite.

Optimization of a one-step method for the multiresidue determination of organophosphorous pesticides in camellia oil.

UNLABELLED: Due to the widespread use and potential toxicity of organophosphorous pesticides (OPs), multiresidue monitoring of OPs in camellia oil has become increasingly important. A simple, rapid, and effective matrix solid-phase dispersion extraction for the determination of 15 organophosphorous pesticides in camellia oil is described. Related important factors influencing the extraction efficiency, such as type of sorbent material, eluting solvent, and ratio of sample/sorbent were studied and optimized. The best results were obtained using 0.5 g of camellia oil, 1.5 g of white carbon black as dispersant sorbent, and 5 mL of acetonitrile: ethyl acetate (2:1, V/V) as eluting solvent. Method validation was performed in order to study sensitivity, linearity, precision, and accuracy. Average recoveries ranged between 76.7% and 102.9% with relative standard deviation values from 2.9% to 13.7% at 2 concentration levels (10 and 100 µg/kg). The method limit of detection at or below the regulatory maximum residue limits for the pesticides was achieved. PRACTICAL APPLICATION: A simple, rapid, and effective method for multiresidue determination of organophosphorous pesticides in camellia oil was developed. The sample preparation could finish in 5 min.

Simultaneous determination of 15 multiresidue organophosphorous pesticides in camellia oil by MSPD-GC-MS.

A one step method based on matrix solid-phase dispersion for simultaneous determination of 15 organophosphorous pesticide residues in camellia oil was developed. The sample preparation could finish in 5 min without extraction procedure, and then analyzed by gas chromatograph-mass spectrometer. Average recoveries ranged between 73.2 % and 108.6 %, with relative standard deviation values (intra-day and inter-day) lower than 16 % at two concentration levels. The method limit of detection was 5 ng/g, which could meet the regulatory maximum residue limits for the pesticides.