Aroma effects of key volatile compounds in Keemun black tea at different grades: HS-SPME-GC-MS, sensory evaluation, and chemometrics.

The present study aimed to explore the relationship between the grade and the characteristic aroma in Keemun black tea (KBT). Headspace solid-phase microextraction (HS-SPME), gas chromatography-mass spectrometry (GC-MS), sensory evaluation, and chemometrics were employed to determine the changes in the flavor evolution of KBT at grade. The results showed that a total of 110 volatile components were identified. Linalool and linalool oxide were dominant. The orthogonal partial least squares discriminant analysis (OPLS-DA) combined with relative odor activity value (rOAV > 0.1) revealed that 11 volatile components were the key volatile compounds of KBT, such as benzeneacetaldehyde (rOAV: 3.43-5.96) and methyl salicylate (rOAV: 2.15 - 2.50). Furthermore, the partial least squares (PLS) model indicated that geraniol, linalool, and methyl salicylate benefited from the reservation of floral flavor of Keemun aroma characteristic of KBT. The findings presented in this thesis add to our understanding of KBT at different grades.

The Efficacy of Vitamin D Supplementation for Migraine: A Meta-Analysis of Randomized Controlled Studies.

INTRODUCTION: The efficacy of vitamin D for migraine remains controversial. We conduct a systematic review and meta-analysis to explore the influence of vitamin D versus placebo on treatment in migraine patients. METHODS: We search PubMed, EMbase, Web of Science, EBSCO, and Cochrane library databases through April 2020 for randomized controlled trials assessing the effect of vitamin D versus placebo on treatment efficacy in migraine patients. This meta-analysis is performed using the random-effect model. RESULTS: Five randomized controlled trials are included in the meta-analysis. Overall, compared with control group in migraine patients, vitamin D treatment is associated with substantially reduced number of headache days (standard mean difference [SMD], -0.53; 95% confidence interval [CI], -0.83 to -0.23; P = 0.0006), frequency of headache attacks (SMD, -1.09; 95% CI, -1.86 to -0.32; P = 0.006), headache severity (SMD, -0.55; 95% CI, -0.91 to -0.19; P = 0.0003), and Migraine Disability Assessment score (SMD, -0.76; 95% CI, -1.11 to -0.40; P < 0.0001). CONCLUSIONS: Vitamin D treatment is effective to alleviate migraine.

[The molecular composition and spectral properties of polysaccharide isolated from pu-erh tea and its material].

Pu-erh tea, a kind of well-known tea from the ancient time, is originally produced in the Yunnan Lanchan River basin through a special solid state fermentation by fungi. It uses sun-dried green tea as its starting materials. To investigate the variation of composition and spectral properties of polysaccharide during solid state fermentation of pu-erh tea by using Saccharomyces cerevisiae as preponderant starter and using sun-dried green tea as materials in the present study. The results showed that the content of water soluble polysaccharide was increased, and the activity of hydrolase such as cellulase, pectinase and glucomylase were also enhanced. The content of neutral sugar increased with the ferment time increasing and the M(w) of raw polysaccharide showed significant difference during fermentation. The main polysaccharide TPS2 and TPS1 were isolated and purified from pu-erh tea and its materials by DEAE-52 and Sephadex G-150 column chromatography. TPS2 contains the higher content of uronic acid, but TPS1 contains the higher contents of neutral sugar and protein. Monosaccharide analysis by GC-MS revealed that TPS1 and TPS2 were composed of arabinose, galactose, glucose, rhamnose, xylose and mannose with molar ratios of 24.2 : 23.6 : 5.9 : 3.2 : 1.8 : 1.1 and 19.3 : 26.9 : 3.2 : 2.7 : 1.3 : 5.5, respectively. The average molecular weight of TPS1 and TPS2 was 1.68 x 10(4) and 1.21 x 10(4) Daltons, respectively. UV scanning spectrum showed that TPS1 and TPS2 had no characteristic absorption between 200 and 400 nm wavelength, it suggested that they contain trace protein. IR spectrum of TPS1 and TPS2 demonstrated that pyranoid rings were contained in them. As shown in the image of atomic force microscope, the molecular appearance of TPS1 and TPS2 resembled islands and apparently consisted of conglomerations. The height of conglomerations of TPS2 was about 40 nm and the length or width was 0.5-0.8 microm, while the height of conglomerations of TPS1 was about 4nm and the length or width was 0.2-0.4 microm. TPS2 shows sheet conglomerations with rough surface, but TPS1 shows squama conglomerations with smooth surface in the image of scanning electron micrograph. The experimental data suggested that the variation of composition and spectral properties of polysaccharide isolated from pu-erh tea and its materials owed to the action of microorganism and humid and thermal action for long time process.

[The quantified analysis of fresh mutton tenderness using PLS methods and Fourier transform near-infrared spectroscopy].

Ninety eight representative fresh mutton samples from Neimeng, Ningxia, Gansu, Xinjiang province were selected for this study, the nondestructive measurement of the fresh mutton tenderness by Fourier transform near infrared (FT-NIR) spectroscopy was discussed. Partial least squares(PLS) algorithm was used to build the model between the shear force value of the fresh mutton tenderness measured by the texture machine and the FT-NIR spectra. The influence of different processing method of spectra, factors and wave regions on the determination coefficients (r2), root mean square error of cross validation (RMSECV) and root mean square error of prediction (RMSEP) was studied. The result showed that the shear force value of ninety eight representative fresh mutton samples was 1.673-6.631 kg, and the shear force value above 75% samples was 2-5 kg, almost covering the fresh mutton tenderness of our country's sheep, the r2 of the calibration could reach 86.2% and the RMSECV was up to 0. 445 in the wave number range 11 995-5 446 cm(-1) and 4 601-4 246 cm(-1) with vector normalization when the PLS factors was ten. The correlation coefficient(R), RMSEP and average bias between value measured by the texture machine and predicted value of model based on validation samples were 0.87, 0.524 and 0.385 respectively. The result indicates that FT-NIR spectroscopy is capable of predicting tenderness value of fresh mutton.

Role of Toll-like receptor 4/NF-kappaB pathway in monocyte-endothelial adhesion induced by low shear stress and ox-LDL.

TLR4 plays an important role in atherosclerosis, but little is known about the precise mechanism. Herein, we investigated the role of TLR4/NF-kappaB signaling pathway in monocyte-endothelial adhesion induced by low shear stress and Ox-LDL. We found that low shear stress up-regulated TLR4 expression in endothelial cells, and that ox-LDL exerted an obvious synergistic action as revealed by RT-PCR and Western blotting analysis. Low shear stress also significantly up-regulated IL-8 expression in endothelial cells. Meanwhile, NF-kappaB activity and the adhesion force of monocytes were increased, and there was a synergetic action of ox-LDL. However, following transfection with a functional mutant of TLR4 (C3H/HeJ, TLR4 Dicd) or addition of anti-human TLR4 mAb, IL-8 expression was obviously decreased, NF-kappaB activity in cells remarkably inhibited, and the adhesion force of monocyte significantly reduced. Nevertheless, anti-human TLR2 mAb had no similar effects. These findings suggest that TLR4 may be involved in the early stages of atherosclerosis, associating ox-LDL, inflammation/infection, and low shear stress. Therefore, TLR4 is expected to be a new target for preventing and treating atherosclerosis.

Influence of different fermentation raw materials on pyrolyzates of Pu-erh tea theabrownin by Curie-point pyrolysis-gas chromatography-mass spectroscopy.

SCOPE: In this study, Pu-erh tea was prepared by solid-state fermentation of the sun-dried green tea, short-fermentation black tea, and black tea. Ultraviolet-visible spectroscopy, infrared spectroscopy and Curie-point pyrolysis-gas chromatography-mass spectroscopy (CP-Py-GC/MS) were used to study the characteristics and chemical compositions of the TB formed in these Pu-erh teas. METHODS AND RESULTS: The pyrolysates of the Pu-erh teas' theabrownin (TB1, TB2, TB3) were analyzed at 386°C using a Curie point pyrolysis instrument. TB1, TB2, and TB3 produced 158, 135 and 148 pyrolysis products, respectively. These compounds could be grouped as follows: alkaloids, 25.23% (TB1), 25.67% (TB2), and 21.91% (TB3); phenols, 24.19% (TB1), 23.08% (TB2), and 29.91% (TB3); nitrogen-compounds, 11.79% (TB1), 11.25% (TB2), and 13.39% (TB3); hydrocarbons, 10.96% (TB1), 10.37% (TB2), and 11.37% (TB3); ketones, 10.34% (TB1), 6.58% (TB2), and 8.22% (TB3); furan, 5.40% (TB1), 4.06% (TB2), and 2.33% (TB3); alcohol, 3.30% (TB1), 4.16% (TB2), and 3.34% (TB3); fatty acids, 2.80% (TB1), 4.03% (TB2), and 1.42% (TB3); esters 2.17% (TB1), 0.99% (TB2) and 2.35% (TB3); and amines 1.61% (TB1), 2.81% (TB2), and 0.86% (TB3). CONCLUSION: Theabrownin mainly contains alkaloids (caffeine), tea pigments, polysaccharides, proteins and lipids. Its precursors include various polyphenols, tea pigments, alkaloids, polysaccharides, proteins and lipids. These compounds in the raw materials impact the chemical composition of theabrownin, and black tea is not a suitable raw fermentation material for Pu-erh tea.

Determination and comparison of γ-aminobutyric acid (GABA) content in pu-erh and other types of Chinese tea.

Two previous studies have reported that pu-erh tea contains a high level of γ-aminobutyric acid (GABA), which is the major inhibitory neurotransmitter in the central nervous system and has several physiological functions. However, two other researchers have demonstrated that the GABA content of several pu-erh teas was low. Due to the high value and health benefits of GABA, analysis of mass-produced pu-erh tea is necessary to determine whether it is actually enriched with GABA. A high-performance liquid chromatography (HPLC) method was developed for the determination of GABA in tea, the results of which were verified by amino acid analysis using an Amino Acid Analyzer (AAA). A total of 114 samples of various types of Chinese tea, including 62 pu-erh teas, 13 green teas, 8 oolong teas, 8 black teas, 3 white teas, 4 GABA teas, and 16 process samples from two industrial fermentations of pu-erh tea (including the raw material and the first to seventh turnings), were analyzed using HPLC. Statistical analysis demonstrated that the GABA content in pu-erh tea was significantly lower than that in other types of tea (p < 0.05) and that the GABA content decreased during industrial fermentation of pu-erh tea (p < 0.05). This mass analysis and comparison suggested GABA was not a major bioactive constituent and resolved the disagreement GABA content in pu-erh tea. In addition, the GABA content in white tea was found to be significantly higher than that in the other types of tea (p < 0.05), leading to the possibility of producing GABA-enriched white tea.

Chemosystematics of tea trees based on tea leaf polyphenols as phenetic markers.

This study examined the polyphenols of tea leaves as chemotaxonomic markers to investigate the phenetic relationship between 89 wild (the small-leaved C.sinensis var. sinensis and large-leaved C. sinensis var. assamica), hybrid, and cultivated tea trees from China and Japan. (-)-Epigallocatechin 3-O-gallate, EGCG (1); (-)-epigallocatechin, EGC (2); (-)-epicatechin 3-O-gallate, ECG (3); (-)-epicatechin, EC (4); (+)-catechin, CA (5); strictinin, STR (6); and gallic acid, GA (7) were used as polyphenolic markers. Of the 13 polyphenol patterns observed, Principal Component Analysis (PCA) indicated that the structure-types of the flavonoid B-rings, such as the pyrogallol-(EGCG (1) and EGC (2)) and catechol-(ECG (3) and EC (4)) types, greatly influenced the classification. Ward's minimum-variance cluster analysis was used to produce a dendrogram that consisted of three sub-clusters. One sub-cluster (A) was composed of old tea trees 'Gushu' cha (C. sinensis var. assamica) and cv 'Taidi' cha, suggesting that relatively primitive tea trees contain greater amounts of compounds 3 and 4 and lower amounts of compounds 1 and 2. The other two sub-clusters B and C, made up of Chinese hybrids (sub-cluster B) and Japanese and Taiwanese tea trees (sub-cluster C), had lower contents of 3 and 4 than sub-cluster A. Therefore, PCA and cluster analysis indicated that the greater the amounts of 1 and 2 (and the lower of 3 and 4), the more recent the origin of the tea line. Based on morphological characteristics, geographical information, and the historical information on tea trees, these results show good agreement with the current theory of tea tree origins, and this suggests that the Xishuangbanna district and Puer City are among the original sites of the tea tree species.