Discrimination and prediction of Qingzhuan tea storage year using quantitative chemical profile combined with multivariate analysis: Advantages of MRMHR based targeted quantification metabolomics.

The duration of storage significantly influences the quality and market value of Qingzhuan tea (QZT). Herein, a high-resolution multiple reaction monitoring (MRMHR) quantitative method for markers of QZT storage year was developed. Quantitative data alongside multivariate analysis were employed to discriminate and predict the storage year of QZT. Furthermore, the content of the main biochemical ingredients, catechins and alkaloids, and free amino acids (FAA) were assessed for this purpose. The results show that targeted marker-based models exhibited superior discrimination and prediction performance among four datasets. The R2Xcum, R2Ycum and Q2cum of orthogonal projection to latent structure-discriminant analysis discrimination model were close to 1. The correlation coefficient (R2) and the root mean square error of prediction of the QZT storage year prediction model were 0.9906 and 0.63, respectively. This study provides valuable insights into tea storage quality and highlights the potential application of targeted markers in food quality evaluation.

A fluorescence ionic probe utilizing Cu2+ assisted competition for detecting glyphosate abused in green tea.

Food fraud caused by the violation of glyphosate use in tea is frequently exposed, posing a potential health risk to consumers and undermining trust in food safety. In the work, an ionic fluorescent probe "[P66614] [4HQCA]-Cu2+ (PHQCA-Cu2+)" was constructed using Cu2+ and ionic liquids coordination through a competitive coordination strategy to detect glyphosate. This probe exhibited a prominent "turn-on" fluorescence response in glyphosate detection. PHQCA-Cu2+was destroyed by glyphosate with its strong coordination capability, and a new complex re-formed simultaneously between glyphosate and the Cu2+ in it, where Cu2+ served as an "invisible indicator" influencing fluorescence changes. Remarkably, PHQCA-Cu2+formed rapidly within 5 s, demonstrated exceptional sensitivity and selectivity, and satisfactory detection performance on paper strips impregnated withPHQCA-Cu2+.Importantly,PHQCA-Cu2+showed excellent recoveries in various green tea, which offered a viable method for identifying contaminated products from the supply chain quickly to enhance overall food safety surveillance.

Three-dimensional fluorescence combined with alternating trilinear decomposition and random forest algorithm for the rapid prediction of species, geographical origin and main components of Glycyrrhizae Radix et Rhizoma (Gancao).

Glycyrrhizae Radix et Rhizoma (Gancao) is a functional food whose quality varies significantly between distinct geographical sources owing to the influence of genetics and the geographical environment. This study employed three-dimensional fluorescence coupled with alternating trilinear decomposition (ATLD) and random forest (RF) algorithms to rapidly predict Gancao species, geographical origins, and primary constituents. Seven fluorescent components were resolved from the three-dimensional fluorescence of the ATLD for subsequent analysis. Results indicated that the RF model distinguished Gancao from various species and origins better than other algorithms, achieving an accuracy of 94.4 % and 88.9 %, respectively. Furthermore, the RF regressor algorithm was used to predict the concentrations of liquiritin and glycyrrhizic acid in Gancao, with 96.4 % and 95.6 % prediction accuracies compared to HPLC, respectively. This approach offers a novel means of objectively evaluating the origin of food and holds substantial promise for food quality assessment.

Revealing the chemical differences and their application in the storage year prediction of Qingzhuan tea by SWATH-MS based metabolomics analysis.

It's generally believed that the longer the storage, the better the quality of dark tea, but the chemical differences of Qingzhuan tea (QZT) with different storage years is still unclear. Herein, in this work, an untargeted metabolomic approach based on SWATH-MS was established to investigate the differential compounds of QZT with 0-9 years' storage time. These QZT samples were roughly divided into two categories by principal component analysis (PCA). After orthogonal projections to latent structures discriminant analysis (OPLS-DA), 18 differential compounds were putatively identified as chemical markers for the storage year variation of QZT. Heatmap visualization showed that the contents of catechins, fatty acids, and some phenolic acids significantly reduced, flavonoid glycosides, triterpenoids, and 8-C N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs) increased with the increase of storage time. Furthermore, these chemical markers were verified by the peak areas corresponding to MS2 ions from SWATH-MS. Based on the extraction chromatographic peak areas of MS and MS2 ions, a duration time prediction model was built for QZT with correlation coefficient R2 of 0.9080 and 0.9701, and RMSEP value of 0.85 and 1.24, respectively. This study reveals the chemical differences of QZT with different storage years and provides a theoretical basis for the quality evaluation of stored dark tea.

A sensitive fluorescence sensor based on a glutathione modified quantum dot for visual detection of copper ions in real samples.

Copper (Cu2+), as a heavy metal, accumulates in the human body to a certain extent, which can induce various diseases and endanger human health. Rapid and sensitive detection of Cu2+ is highly desired. In present work, a glutathione modified quantum dot (GSH-CdTe QDs) was synthesized and applied in a "turn-off" fluorescence probe to detect Cu2+. The fluorescence of GSH-CdTe QDs could be rapidly quenched in the presence of Cu2+ through aggregation-caused quenching (ACQ), resulting from the interaction between the surface functional groups of GSH-CdTe QDs and Cu2+ and the electrostatic attraction. In the range of 20-1100 nM, the Cu2+ concentration showed a good linear relationship with the fluorescence decline of the sensor, and the LOD is 10.12 nM, which was lower than the U.S. Environmental Protection Agency (EPA) defined limit (20 µM). Moreover, aiming to attain visual analysis, colorimetric method was also used for rapidly detecting Cu2+ by capturing the change in fluorescence color. Interestingly, the proposed approach has successfully been applied for the detection of Cu2+ in real samples (i.e., environment water, food and traditional Chinese medicine) with satisfactory results, which provides a promising strategy for the detection of Cu2+ in practical application with the merits of being rapid, simple and sensitive.

Fast and non-destructive discriminating the geographical origin of Hangbaiju by hyperspectral imaging combined with chemometrics.

Hangbaiju is highly appreciated flower tea for its health benefits, and its quality and price are affected by geographical origin. Fast and accurate identification of the geographical origin of Hangbaiju is very significant for producers, consumers and market regulators. In this work, hyperspectral imaging combined with chemometrics, was used, for the first time, to explore and implement the geographical origin classification of Hangbaiju. The hyperspectral images in the spectral range of 410-2500 nm for 75 samples of five different origins were collected. As a versatile chemometrics tool, bagging classification tree-radial basis function (BAGCT-RBFN), compared with classification tree (CT), radial basis function network (RBFN), was applied to discriminate Hangbaiju samples from different origins. The results showed that BAGCT-RBFN based on optimal wavelengths yielded superior classification performances to CT and RBFN with full wavelengths. The recognition rates (RR) of the training and prediction sets by BAGCT-RBFN were 96.0 % and 92.0 %, respectively. Hyperspectral imaging combined with chemometric can be considered as a powerful, feasible and convenient tool for the classification of Hangbaiju samples from different origins. It promises to be a potential way for origin discriminant analysis and quality monitor in food fields.

The Clostridium Metabolite P-Cresol Sulfate Relieves Inflammation of Primary Biliary Cholangitis by Regulating Kupffer Cells.

OBJECTIVE: To study the effect and mechanism of the Clostridium metabolite p-Cresol sulfate (PCS) in primary biliary cholangitis (PBC). METHODS: Gas chromatography-mass spectrometry (GC-MS) was used to detect differences in tyrosine, phenylalanine, tryptophan, PCS, and p-Cresyl glucuronide (PCG) between the serum of PBC patients and healthy controls. In vivo experiments, mice were divided into the normal control, PBC group, and PBC tyrosine group. GC-MS was used to detect PCS and PCG. Serum and liver inflammatory factors were compared between groups along with the polarization of liver Kupffer cells. Additionally, PCS was cultured with normal bile duct epithelial cells and Kupffer cells, respectively. PCS-stimulated Kupffer cells were co-cultured with lipopolysaccharide-injured bile duct epithelial cells to detect changes in inflammatory factors. RESULTS: Levels of tyrosine and phenylalanine were increased, but PCS level was reduced in PBC patients, with PCG showing a lower concentration distribution in both groups. PCS in PBC mice was also lower than those in normal control mice. After oral administration of tyrosine feed to PBC mice, PCS increased, liver inflammatory factors were decreased, and anti-inflammatory factors were increased. Furthermore, Kupffer cells in the liver polarized form M1 transitioned to M2. PCS can damage normal bile duct epithelial cells and suppress the immune response of Kupffer cells. But PCS protects bile duct epithelial cells damaged by LPS through Kupffer cells. CONCLUSIONS: PCS produced by Clostridium-metabolized tyrosine reduced PBC inflammation, suggesting that intervention by food, or supplementation with PCS might represent an effective clinical strategy for treating PBC.

Antioxidant properties of polyphenols from snow chrysanthemum (Coreopsis tinctoria) and the modulation on intestinal microflora in vitro.

CONTEXT: Coreopsis tinctoria Nutt (Asteraceae), named snow chrysanthemum, is known to have a high level of polyphenols. However, the potential prebiotic effect on modulating intestinal microflora is still unclear. OBJECTIVE: The chemical composition, antioxidant properties of snow chrysanthemum polyphenols (SCPs) and their effects on human intestinal microbiota were investigated. MATERIALS AND METHODS: SCPs were extracted using ultrasonic-assisted extraction, and further determined using UPLC-QE Orbitrap/MS. Five assays were used to investigate the antioxidant activities of SCPs. Subsequently, the effects of SCPs on intestinal microbiota in vitro were determined by high throughput sequencing and bioinformatics analysis. RESULTS: Marein, isookanin and cymaroside were the major phenolic compounds, which accounted for 42.17%, 19.53% and 12.25%, respectively. Marein exhibited higher scavenging capacities in DPPH (EC50 = 8.84 µg/mL) and super anion radical assay (EC50 = 282.1 µg/mL) compared to cymaroside and isookanin. The antioxidant capacity of cymaroside was weakest among the three phenolic compounds due to the highest EC50 values, especially for superoxide anion radical assay, EC50 > 800 µg/mL. The result of in vitro fermentation showed that the three phenolic compounds increased the relative abundances of Escherichia/Shigella, Enterococcus, Klebsiella, etc., and isookanin notably increased the relative abundance of Bifidobacterium and Lactobacillus. DISCUSSION AND CONCLUSIONS: SCPs exhibited antioxidant properties and potential prebiotic effects on modulating the gut microbiota composition. The findings indicated that SCPs consumption could exert prebiotic activity that is beneficial for human health.

Colorimetric assay based on peroxidase-like activity of dodecyl trimethylammonium bromide-tetramethyl zinc (4-pyridinyl) porphyrin for detection of organophosphorus pesticides.

A simple and sensitive colorimetric assay for detecting organophosphorus pesticides (OPs) was developed based on 3,3',5,5'-tetramethylbenzidine (TMB)/hydrogen peroxide (H2O2)/dodecyl trimethylammonium bromide (DTAB)-tetramethyl zinc (4-pyridinyl) porphyrin (ZnTPyP). In this system, based on the peroxidase-like activity of DTAB-ZnTPyP, H2O2 decomposes to produce hydroxyl radicals, which oxidize TMB, resulting in blue oxidation products. The OPs (trichlorfon, dichlorvos, and thimet) were first combined with DTAB-ZnTPyP through electrostatic interactions. The OPs caused a decrease in the peroxidase-like activity of DTAB-ZnTPyP due to spatial site blocking. At the same time, π-interactions occurred between them, and these interactions also inhibited the oxidation of TMB (652 nm), thus making the detection of OPs possible. The limits of detection for trichlorfon, dichlorvos, and thimet were 0.25, 1.02, and 0.66 µg/L, respectively, and the corresponding linear ranges were 1-35, 5-45, and 1-40 µg/L, respectively. Moreover, the assay was successfully used to determine OPs in cabbage, apple, soil, and traditional Chinese medicine samples (the recovery ratios were 91.8-109.8%), showing a great promising potential for detecting OPs also in other complex samples.

Dual channel sensor array based on ZnCdSe QDs - KMnO4: An effective tool for analysis of catechins and green teas.

A novel dual-channel sensor array based on the "off" and "off-on" phenomenon of ZnCdSe quantum dots (QDs) - KMnO4 system was established for the effective distinguish of 30 green teas with various species, grades and origins. Starting from optimization of QDs for the construction of the sensing system, their sensitivity and selectivity performances towards 10 representative green teas were tested first and the sensor systems based on ZnCdSe QDs were finally established. An obvious "off" response brought by the interactions between amino acids, quercetin, et al. and ZnCdSe QDs was obtained while an "off-on" phenomenon brought by the interactions between catechins and the ZnCdSe-KMnO4 system had also been verified. Furthermore, based on the differential fluorescence "off-on" response of seven catechins, the qualitative and quantitative analyses of these catechins were successfully carried out with the linear range from 0.5 to 10 µg/mL. Most importantly, through adopting the dual-channel sensor, 30 green teas with different species, origins and grades can be accurately identified with the LDA model according to the spectral signals and the recognition accuracy could achieve 100 %.

Chemistry Combining Elemental Profile, Stable Isotopic Ratios, and Chemometrics for Fine Classification of a Chinese Herb Licorice (Glycyrrhiza uralensis Fisch.) from 37 Producing Area.

A method based on elemental fingerprint, stable isotopic analysis and combined with chemometrics was proposed to trace the geographical origins of Licorice (Glycyrrhiza uralensis Fisch) from 37 producing areas. For elemental fingerprint, the levels of 15 elements, including Ca, Cu, Mg, Pb, Zn, Sr, Mn, Se, Cd, Fe, Na, Al, Cr, Co, and K, were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). Three stable isotopes, including δ 13C, δ 15N, and δ 18O, were measured using an isotope-ratio mass spectrometer (IRMS). For fine classification, three multiclass strategies, including the traditional one-versus-rest (OVR) and one-versus-one (OVO) strategies and a new ensemble strategy (ES), were combined with two binary classifiers, partial least squares discriminant analysis (PLSDA) and least squares support vector machines (LS-SVM). As a result, ES-PLSDA and ES-LS-SVM achieved 0.929 and 0.921 classification accuracy of GUF samples from the 37 origins. The results show that element fingerprint and stable isotope combined with chemometrics is an effective method for GUF traceability and provides a new idea for the geographical traceability of Chinese herbal medicine.

[Research progress on common pesticide residues in Chinese medicinal materials].

Chinese medicinal materials are the precious resources of China and favored by patients at home and abroad because of their natural sources and curative effects. Pesticides are often used to prevent and control diseases and insect pests and regulate the growth of Chinese medicinal plants, so as to improve the yield and quality of Chinese medicinal materials. Most of the pesticides can play a role in pest control through systemic action, stomach toxicity, contact, fumigation and other ways, especially the systemic pesticides can kill hidden pests by entering the Chinese medicinal plants. Despite the good pest control effect, it is difficult to remove the systemic pesticides by simple cleaning, which poses a great risk to the safety of Chinese medicinal materials. At the same time, excessive or non-standard use of pesticides leads to serious pesticide residues in Chinese medicinal materials, which affects not only the quality and efficacy of the materials and harm human health but also the international development of Chinese medicinal materials industry. Pesticide residues have become a bottleneck affecting the industry development and hindering the export of Chinese medicinal materials. Therefore, it is of great significance to study how to quickly, sensitively, and accurately detect and remove pesticide residues in Chinese medicinal materials. We reviewed the common pesticide residues in Chinese medicinal materials in recent years in terms of characteristics, harm, and detection and removal techniques, and discussed the future development of the detection and removal deve-lopment. With this review, we aimed to provide a reference for the quality control of Chinese medicinal materials and promote the healthy development of Chinese medicine industry.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry combined with chemometrics to identify the origin of Chinese medicinal materials.

Geographical origin and authenticity are two core factors to promote the development of traditional Chinese medicine (TCM) herbs perception in terms of quality and price. Therefore, they are important to both sellers and consumers. Herein, we propose an efficient, accurate method for discrimination of genuine and non-authentic producing areas of TCM by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Take Atractylodes macrocephala Koidz (AMK) of compositae as an example, the MALDI-TOF MS spectra data of 120 AMK samples aided by principal component analysis-linear discriminant analysis (PCA-LDA), partial least squares discriminant analysis (PLS-DA) and random forest (RF) successfully differentiated Zhejiang province, Anhui province and Hunan province AMK according to their geographical location of origin. The correct classification rates of test set were above 93.3%. Furthermore, 5 recollected AMK samples were used to verify the performance of the classification models. The outcome of this study can be a good resource in building a database for AMK. The combined utility of MALDI-TOF MS and chemometrics is expected to be expanded and applied to the origin traceability of other TCMs.

Rapid identification of the geographical origin of Eucommia ulmoides by using excitation-emission matrix fluorescence combined with chemometric methods.

Eucommia ulmoides is an important and valuable traditional Chinese medicine with various medical functions, and has been widely used as health food in China, Japan, South Korea and other Asian countries for many years. The efficacy and quality of E. ulmoides are closely associated with the geographical origin. In this work, the potential of excitation-emission matrix (EEMs) fluorescence coupled with chemometric methods was investigated for simple, rapid and accurate for identification E. ulmoides from different geographical origins. Parallel factor analysis (PARAFAC) was applied for characterizing the fluorescence fingerprints of E. ulmoides samples. Moreover, k-nearest neighbor (kNN), principal component analysis-linear discriminant analysis (PCA-LDA) and partial least squares discriminant analysis (PLS-DA) models were used for the classification of E. ulmoides samples according to their geographical origins. The results showed that kNN model was more suitable for identification of E. ulmoides samples from different provinces. The kNN model could identify E. ulmoides samples from eight different geographical origins with 100% accuracy on the training and test sets. Therefore, the proposed method was available for conveniently and accurately determining the geographical origin of E. ulmoides, which can expect to be an attractive alternative method for identifying the geographic origin of other traditional Chinese medicines.

Accurate identification of the geographical origins of lily using near-infrared spectroscopy combined with carbon dot-tetramethoxyporphyrin nanocomposite and chemometrics.

Near-infrared spectroscopy technique is a prevailing tool for quality control of foods and traditional Chinese medicines. However, it usually faced the problems of severe peak overlap, low classification accuracy and poor specificity. In this work, the potential of carbon dot-tetramethoxyporphyrin nanocomposite-based nano-effect near-infrared spectroscopy sensor combined with chemometric method was investigated for the accurate identification lily from different geographical origins. Partial least squares-discriminant analysis (PLS-DA) was used for differentiating geographical origins of lily based on the collected traditional and nano-effect near-infrared spectroscopy. Compared with traditional near-infrared spectroscopy, the nano-effect near-infrared spectroscopy obtains superior classification performance with 100% accuracy on the training and test set. The results showed that the proposed method based on near-infrared spectroscopy combined with nanocomposites and chemometrics could be considered as a promising tool for rapid discrimination of the authenticity of food and traditional Chinese medicine in the future.

Maillard reaction products and guaiacol as production process and raw material markers for the authentication of sesame oil.

BACKGROUND: Sesame oil has an excellent flavor and is widely appreciated. It has a higher price than other vegetable oils because of the high price of its raw materials, and different processing techniques also result in products of different quality levels, which can command different prices. In the market, there is a persistent problem of adulteration of sesame oil, driven by economic interests. The screening of volatile markers used to distinguish the authenticity of sesame oil raw materials and production processes is therefore very important. RESULTS: In this work, six markers related to the production processes and raw materials of sesame oil were screened by gas chromatography-tandem mass spectrometry (GC-MS/MS) combined with chemometric analysis. They were 3-methyl-2-butanone, 2-ethyl-5-methyl-pyrazine, guaiacol, 2,6-dimethyl-pyrazine, 5-methyl furfural, and ethyl-pyrazine. The concentration of these markers in sesame oil is between 10 and1000 times that found in other vegetable oils. However, only 3-methyl-2-butanone and 2-ethyl-5-methyl-pyrazine differed significantly as the result of the use of different production processes. Except for guaiacol, which was mainly derived from raw materials, the other five compounds mentioned above all result from the Maillard reaction during thermal processing. The six compounds mentioned above are sufficient to distinguish fraud involving sesame oil raw materials and production processes, and can identify accurately adulteration levels of 30% concentration. CONCLUSION: In this study, the classification markers can identify the adulteration of sesame oil accurately. These six compounds are therefore important for the authenticity of sesame oil and provide a theoretical basis for the rapid and accurate identification of the authenticity of sesame oil. © 2021 Society of Chemical Industry.

Geographical origin traceability of traditional Chinese medicine Atractylodes macrocephala Koidz. by using multi-way fluorescence fingerprint and chemometric methods.

Atractylodes macrocephala Koidz. (AM) is an important plant of traditional Chinese medicine (TCM), and its status can be comparable with ginseng in China. The efficacy and quality of AM are closely related to the place of origin. Hence, we proposed a simple and fast strategy to classify AM from different geographical origins by using multi-way fluorescence fingerprint combined with chemometric methods. AM samples with different dilution levels have different fluorescence characteristics, resulting from different content of fluorescence components and chemical microenvironment. Therefore, AM samples were diluted 5-fold, 10-fold, and 20-fold with 40% ethanol aqueous solution to obtain excitation-emission matrix data, and multi-way (three-way and four-way) data arrays were constructed. And then, the fluorescence fingerprints of AM samples were characterized by three-way and four-way parallel factor analysis (PARAFAC). In addition, four pattern recognition methods were used to classify AM from different provinces. The results show that the four-way data array can provide more abundant information than three-way data arrays, so it is more conducive to sample classification. According to the results obtained from the analysis of four-way data array, the correct classification rate (CCR) of the cross-validation and prediction set obtained by partial least squares-discrimination analysis (PLS-DA) were 90.5% and 100%, respectively. To sum up, the proposed method can be regarded as a powerful, feasible, convenient, reliable, and universal classification tool for the classification of AM samples from different provinces and can be used as a promising method to realize the geographical origin traceability of other TCMs.

The Efficacy of Triptolide in Preventing Diabetic Kidney Diseases: A Systematic Review and Meta-Analysis.

Ethnopharmacological Relevance: Triptolide (TP), the primary biologically active ingredient of Tripterygium wilfordii Hook F (TWHF), possesses the potential to solve the shortcomings of TWHF in treating diabetic kidney disease (DKD) in the clinic. Aim of the Study: We conducted a meta-analysis to evaluate the efficacy of TP in treating DKD and offer solid evidence for further clinical applications of TP. Materials and Methods: Eight databases (CNKI, VIP, CBM, WanFang, PubMed, Web of Science, EMBASE, and Cochrane library) were electronically searched for eligible studies until October 17, 2020. We selected animal experimental studies using TP versus renin-angiotensin system inhibitors or nonfunctional liquids to treat DKD by following the inclusion and exclusion criteria. Two researchers independently extracted data from the included studies and assessed the risk of bias with the Systematic Review Centre for Laboratory Animal Experimentation Risk of Bias tool. Fixed-effects meta-analyses, subgroup analyses, and meta-regression were conducted using RevMan 5.3 software. Inplasy registration number: INPLASY2020100042. Results: Twenty-six studies were included. Meta-analysis showed that TP significantly reduced albuminuria (14 studies; standardized mean difference SMD: -1.44 [-1.65, -1.23], I2 = 87%), urine albumin/urine creatinine ratio (UACR) (8 studies; SMD: -5.03 [-5.74, -4.33], I2 = 84%), total proteinuria (4 studies; SMD: -3.12 [-3.75, -2.49], I2 = 0%), serum creatinine (18 studies; SMD: -0.30 [-0.49, -0.12], I2 = 76%), and blood urea nitrogen (12 studies; SMD: -0.40 [-0.60, -0.20], I2 value = 55%) in DKD animals, compared to the vehicle control. However, on comparing TP to the renin-angiotensin system (RAS) inhibitors in DKD treatment, there was no marked difference in ameliorating albuminuria (3 studies; SMD: -0.35 [-0.72, 0.02], I2 = 41%), serum creatinine (3 studies; SMD: -0.07 [-0.62, 0.48], I2 = 10%), and blood urea nitrogen (2 studies; SMD: -0.35 [-0.97, 0.28], I2 = 0%). Of note, TP exhibited higher capacities in reducing UACR (2 studies; SMD: -0.66 [-1.31, -0.01], I2 = 0%) and total proteinuria (2 studies; SMD: -1.18 [-1.86, -2049], I2 = 0%). Meta-regression implicated that the efficacy of TP in reducing DKD albuminuria was associated with applied dosages. In addition, publication bias has not been detected on attenuating albuminuria between TP and RAS inhibitors after the diagnosis of DKD. Systematic Review Registration: https://clinicaltrials.gov/, identifier INPLASY2020100042.

Visual paper-based sensor for the highly sensitive detection of caffeine in food and biological matrix based on CdTe-nano ZnTPyP combined with chemometrics.

Caffeine naturally occurs in tea and cocoa, which is also used as an additive in beverages and has pharmacological effects such as refreshing, antidepressant, and digestion promotion, but excessive caffeine can cause harm to the human body. In this work, based on the specific response between nano zinc 5, 10, 15, 20-tetra(4-pyridyl)-21H-23H-porphine (nano ZnTPyP)-CdTe quantum dots (QDs) and caffeine, combined with chemometrics, a visual paper-based sensor was constructed for rapid and on-site detection of caffeine. The fluorescence of QDs can be quenched by nano ZnTPyP. When caffeine is added to the system, it can pull nano ZnTPyP off the surface of the QDs to achieve fluorescence recovery through electrostatic attraction and nitrogen/zinc coordination. The detection range is 5 × 10-11~3 × 10-9 mol L-1, and the detection limit is 1.53 × 10-11 mol L-1 (R2 = 0.9990) (S/N = 3). The paper-based sensor constructed exhibits good results in real samples, such as tea water, cell culture fluid, newborn bovine serum, and human plasma. Therefore, the sensor is expected to be applied to the rapid instrument-free detection of caffeine in food and biological samples.Graphical abstract.

Determination of l-theanine in tea water using fluorescence-visualized paper-based sensors based on CdTe quantum dots/corn carbon dots and nano-porphyrin with chemometrics.

BACKGROUND: The quality of tea is influenced by numerous factors, especially l-theanine, which is one of the important markers used to evaluate the sweetness and freshness of tea. Sensitive, rapid, and accurate detection of l-theanine is therefore useful to identify the grade and quality of tea. RESULTS: A high-sensitivity, paper-based fluorescent sensor combined with chemometrics was established to detect l-theanine in tea water based on CdTe quantum dots / corn carbon dots and nano tetra pyridel-porphine zinc (ZnTPyP). To verify the reliability of this method, fluorescence spectra and fluorescence-visualized paper-based sensors were compared. The fluorescence spectrum method demonstrated a linear range of 1 to 10 000 nmol L-1 and a limit of detection (LOD) of 0.19 nmol L-1 . In the fluorescence-visualized paper-based sensors there was a linear range of 10-1000 nmol L-1 , and the LOD was 10 nmol L-1 . Partial least squares discriminant analysis (PLSDA) and partial least squares regression analysis (PLSR) were used successfully to determine l-theanine accurately in tea water with this approach. The accuracy of the PLSDA model was 100% both in the training set and the predicting set, and the correlation coefficient between the actual concentration and the predicted concentration was greater than 0.9997 in the PLSR model. CONCLUSION: This fluorescence-visualized paper-based sensor, combined with chemometrics, could be applied efficiently to the practical analysis of tea water samples, which provides a new idea to ensure the flavor and quality of tea. © 2020 Society of Chemical Industry.