In vitro assessment of major and trace element bioaccessibility in tea samples

Determination of copper and cobalt in different tea samples at trace levels by FAAS after preconcentration with a novel iron PAMAM-OH-encapsulated magnetic nanoparticle as SPE sorbent

Environmental contamination caused by heavy metals is a significant global concern. The presented study investigated the efficiency of iron PAMAM-OH encapsulated magnetic nanoparticles (Fe-MNP-G2-OH) as sorbent for the preconcentration of copper and cobalt from tea samples. High metal-chelating ethylenediamine core polyamidoethanol generation-2 (PAMAM-G2-OH) was encapsulated with iron oxide (Fe3O4) to synthesize the sorbent. Limit of detection (LOD) values for copper and cobalt extracted and detected by the developed Fe-MNP-G2-OH -SPE-FAAS method were 0.52 and 1.1 μg L-1, respectively. There were 230- and 101-fold improvement in detection limits for copper and cobalt, respectively, when compared to direct FAAS measurement. The percent recovery results for the analytes in green and black tea samples ranged from 93 to 107%, with low relative standard deviation (%RSD) values. The synthesis of nanoparticle was carried out through a unique method, which was characterized by thermogravimetric analysis (TGA), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) methods. The analytical results demonstrated the applicability and effectiveness of Fe-MNP-G2-OH nanoparticles on the preconcentration of copper and cobalt from tea samples and the developed method is suitable for the trace detection of heavy metals by FAAS method. To the best our knowledge, this is the first study where copper and cobalt in green and black tea samples were extracted by Fe-MNP-G2-OH adsorbent and precipitation of the adsorbent during its synthesis was carried out in acetone medium rather than aqueous one.

Assessment on Solubility and Solid Phase Chemical Fractionation of Manganese in Hot Infusions of Green and Roasted Mate

A solid phase chemical fractionation (SPCF) of the Mn in hot infusions prepared from commercial samples of roasted (RM) and green mate (GM) using a chelating resin Chelex 100 (NH4+ form) was performed to assess the relative lability of this essential trace element (ETE). In addition, total Mn contents in the RM and GM samples and their infusions were determined by flame atomic absorption spectrometry. Total polyphenol (TP) contents and the presence of soluble melanoidins (SM) were correlated with the Mn solubility in the RM and GM infusions. From the SPCF study, it was possible to observe that the soluble Mn forms in the mate infusions were essentially associated with relatively noninert chemical species (98.4-99.7%), suggesting that they may be potentially bioavailable. In addition, the soluble Mn contents in the GM infusions were 20.5% higher than those found in the RM. Mn solubility in the (RM) infusions was highly and directly correlated (r = 0.99) with the soluble TP, while in the GM infusions, it was high and inversely correlated with soluble TP (r =  -0.87). On the other hand, Mn solubility in the RM and GM infusions was weakly correlated with the SM. It should be stressed that GM infusions can contribute with 57 and 44% more than the RM infusions to the recommended adequate intake of Mn established for females and males, respectively. Moreover, this work is the first to evaluate and compare the relative lability of Mn and its solubility in the RM and GM infusions.

Comparison of the Potential Relative Bioaccessibility of Zinc Supplements-In Vitro Studies

The aim of this study was to determine the potential relative bioaccessibility of zinc (Zn) from selected dietary supplements during in vitro digestion. The bioaccessibility of Zn was evaluated in dietary supplements differing in the pharmaceutical form, content, dose, and chemical form of the element. The content of Zn was determined by flame atomic absorption spectrometry. The applied method was validated, and results were characterised by good linearity (R² = 0.998), recovery (109%), and accuracy (0.02%). As a result of the tests conducted, it was found that the bioaccessibility of Zn from dietary supplements varied and ranged from 1.1% to 9.4%. The highest bioaccessibility was found for zinc diglycinate and the lowest for zinc sulphate. In 9 out of 10 tested dietary supplements, the determined Zn content was higher than the one declared by the producer (up to 161%). The estimated tolerable upper intake level (UL) was exceeded by five of the analysed dietary supplements (123-146%). The analysed dietary supplements were assessed in terms of compliance with the information contained on the product packaging, based on current Polish and European legal regulations. The qualitative assessment was performed according to the United States Pharmacopoeia (USP) guidelines.

Quality Characteristics of Karst Plateau Tea (Niaowang) in Southwest China and Their Relationship with Trace Elements

This study investigated the relationship between the characteristics of quality components and trace elements of Niaowang tea from Guizhou Province in mountainous plateau areas. The contents of catechin monomers and eight other trace elements were measured using high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The results showed that the tender summer leaves of Niaowang tea in Guizhou Province had the highest content of catechins at 3558.15~2226.52 μg·g^-1. The content of ester catechins was the highest in summer, amounting to 69.75~72.42% of the total catechins. The content of non-ester catechins was the highest in autumn, reaching 52.54~62.28% of the total catechins; among ester catechins, the mass fraction of epigallocatechin gallate (EGCG) showed a pattern of mature summer leaves > tender summer leaves > mature autumn leaves > tender autumn leaves, and the mass fractions of gallocatechin gallate (GCG) and epicatechin gallate (ECG) were larger in autumn than in summer; gallocatechin (GC) had no significant correlation with different trace elements, and Mn had no significant correlations with different catechin monomers. EGCG was significantly negatively correlated with As, Se, Hg, Pb, Ni, and Zn. Additionally, gallic acid (GA) was significantly negatively correlated with As, Hg and Ni. Other catechin monomers were largely significantly positively correlated with trace elements. The biochemical indicators of the phenotype of Niaowang tea show that the summer and autumn buds are suited for making high-quality green tea.

Preparation of Zn-Gly and Se-Gly and Their Effects on the Nutritional Quality of Tea (Camellia sinensis)

BACKGROUND

Micronutrient malnutrition affects millions of people due to a lack of Zn and Se.

METHODS

The process conditions for the manufacture of glycine-chelated sodium selenite (Se-Gly) and zinc sulfate heptahydrate (Zn-Gly) were studied. The effects of ligand concentration, pH, reaction ratio, reaction temperature, and reaction time on fertilizer stability were assessed. The effects of Zn-Gly and Se-Gly on tea plants were determined.

RESULTS

Orthogonal experiments showed that the optimal preparation conditions for Zn-Gly (75.80 % Zn chelation rate) were pH 6.0, ligand concentration 4 %, reaction ratio 1:2, reaction time 120 min, reaction temperature 70 ℃. The optimal preparation conditions for Se-Gly (56.75 % Se chelation rate) were pH 6.0, ligand concentration 10%, reaction ratio 2:1, reaction time 40 min, temperature 50 ℃. Each chelate was completely soluble in water and verified by infrared spectroscopy and ultraviolet spectroscopy.

CONCLUSIONS

Zn-Gly and Se-Gly increased the Zn and Se content in tea plants, and foliar application was more effective than soil application. Combined application of Zn-Gly and Se-Gly was more effective than Zn-Gly or Se-Gly alone. Our findings suggest that Zn-Gly and Se-Gly provide a convenient method of addressing human Zn and Se deficiency.

Relationship between Total Phenolic Content, Antioxidant Capacity, Fe and Cu Content from Tea Plant Samples at Different Brewing Times

The purpose of this study was to investigate the antioxidant capacity of different tea plant: mint, linden, chamomile, St. John’s wort, green and black tea in relation to total phenolic content. The antioxidant capacity of the tea infusions at different brewing times was determined using DPPH assay while the total phenolic content (TPC) was assessed using the modified Folin-Ciocalteu method. The results showed that there were significant statistical differences in antioxidant capacity depending on infusion time, according to one-way ANOVA analysis. Leaves used as components of tea infusions were analyzed by FAAS for their content of iron and copper in the dry product and in the infusion. The correlation between TPC and DPPH capacity of tea plant infusions was evaluated by Pearson correlation matrix. Total phenolics compounds content was positively and significantly correlated with DPPH capacity for all infusions time. Significant correlation was observed between TPC and the copper concentration (p < 0.05). Consequently, the correlations between the physicochemical parameters, TPC, DPPH capacity, Fe and Cu content suggested that the TPC may be a good indicator of the DPPH capacity in the tea infusions and also, suggested the influence of antioxidant compounds on mineral bioavailability.