Investigations of the highly efficient processing technique, chemical constituents, and anti-inflammatory effect of N-ethyl-2-pyrrolidinone-substituted flavan-3-ol (EPSF)-enriched white tea

N-Ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs) are a newly discovered compound class in tea with various bioactivities. This study aimed to develop a novel processing technique to enhance EPSF contents in white tea efficiently. Using optimal processing parameters of 125 °C and 30 min in a high-temperature sterilizing oven, total EPSF content significantly increased by 1.42-18.80-fold to 1.57-6.22 mg/g without impacting sensory characteristics. Metabolomics analysis revealed elevated levels of nucleosides, nucleotides, bases, theaflavins, flavonol aglycones, EPSFs, and most flavone-C-glycosides, as well as decreased levels of amino acids, procyanidins, theasinensins, several flavanols, and flavonol-O-glycosides after EPSF-enrichment treatment. Furthermore, the EPSF-enriched white tea exhibited notable anti-inflammatory effects, mitigating xylene-induced ear edema in mice and carrageenan-induced paw edema and cotton ball-induced granulomas in rats. This study developed a new processing technique for highly efficient enhancement of EPSFs in white tea and demonstrated that EPSF-enriched white tea has a potential to serve as effective anti-inflammatory dietary supplement.

Positive contributions of the stem to the formation of white tea quality-related metabolites during withering

Most teas, including white tea, are produced from tender shoots containing both leaf and stem. However, the effect of the stem on white tea quality remains unclear, especially during withering, an essential process. Therefore, this study investigated the withering-induced changes in the leaves and stems of Camellia sinensis cv. 'Fudingdabai' by multi-group analysis. During withering, the levels of catechin and theobromine (i.e., major flavor-related compounds) decreased slightly, mainly in the leaves. The abundance of some proteinaceous amino acids related to fresh taste increased in stems due to increased protein hydrolysis. In addition, changes in biosynthetic pathways caused a decrease in theanine (a major non-proteinaceous amino acid) and an increase in gamma-aminobutyric acid in stems. Terpenes, mainly in the stems, were partially affected by withering. Phenylacetaldehyde, a major contributor to white tea aroma, increased mainly in the stems. These findings reflect the positive contribution of the stem to white tea quality.

Comprehensive comparison of aroma profiles and chiral free and glycosidically bound volatiles in Fujian and Yunnan white teas

The Fujian and Yunnan provinces in China are the most representative origins of white tea. However, the key differences in the chemical constituents of the two white teas have rarely been revealed. In this study, a comprehensive comparison of the aroma profiles, chiral volatiles, and glycosidically bound volatiles (GBVs) in Fujian and Yunnan white teas was performed, and 174 volatiles and 28 enantiomers, including 22 volatiles and six GBVs, were identified. Linalool, linalyl-β-primeveroside (LinPrim), and α-terpineol presented the opposite dominant configurations in Fujian and Yunnan white teas, and the chiral GBVs were firstly quantified with significant differences in the contents of R-LinPrim and β-d-glucopyranosides of (2R, 5R)-linalool oxide A and (2R, 5S)-linalool oxide B. Moreover, discrimination functions for Fujian and Yunnan white teas were created using nine key variables with excellent reliability and efficiency. These results provide a new method for objectively distinguishing authentic white teas according to geographical origin.

The metabolic mechanism of flavonoid glycosides and their contribution to the flavor evolution of white tea during prolonged withering

This study was the first to comprehensively investigate the metabolic mechanism of flavonoid glycosides (FGs) and their contribution to flavor evolution during white tea processing using quantitative descriptive analysis, metabolomics, dose-over-threshold factors and pseudo-first-order kinetics. A total of 223 flavonoids were identified. Total FGs decreased from 7.02 mg/g to 4.35 mg/g during processing, compared to fresh leaves. A total of 86 FGs had a significant impact on the flavor evolution and 9 key flavor FGs were identified. The FG biosynthesis pathway was inhibited during withering, while the degradation pathway was enhanced. This promoted the degradation of 9 key flavor FGs following pseudo-first-order kinetics during withering. The degradation of the FGs contributed to increase the taste acceptance of white tea from -4.18 to 1.32. These results demonstrated that water loss stress during withering induces the degradation of key flavor FGs, contributing to the formation of the unique flavor of white tea.

Metabolomics investigation of the chemical variations in white teas with different producing areas and storage durations

In this study, we employed nontargeted metabolomics and quantitative analysis to explore the variations in metabolites among white teas from different production areas and with varying storage durations. A total of 83 compounds exhibited differential levels between Zhenghe and Fuding white tea, 89 between Zhenghe and Jinggu, and 75 between Fuding and Jinggu white tea. Concerning the storage of white tea, the concentrations of flavanols, dimeric catechins, and amino acids decreased over time, while N-ethyl-2-pyrrolidone-substituted flavanols (EPSFs), caffeine, adenosine monophosphate (AMP), and adenosine increased. Galloylated flavanols showed a higher propensity to form EPSFs with theanine compared to nongalloylated flavanols during storage. Theanine and epigallocatechin gallate were more inclined to generate S-configuration EPSFs during storage in Fuding and Jinggu white tea samples, while R-configuration EPSFs were more readily formed in Zhenghe white tea samples. This study offers a comprehensive understanding of the changes in metabolites during the storage of white tea.

Study on the dynamic change of volatile components of white tea in the pile-up processing based on sensory evaluation and ATD-GC-MS Technology

The pile-up processing has a great impact on the flavor of white tea. To investigate the effects of the volatile accumulation of white tea with different piling thickness treatments, tea leaves from different thickness treatments were subjected to sensory quantitative description analysis and ATD-GC-MS detection in this study. As a result, 122 volatile components were identified from white tea with different treatments. A total of 8 key compounds, including isovaleraldehyde, isobutyraldehyde, 2-methyl-butanal, 1-octene-3-ol, linalool, pentanoic acid, hexanal and 1-hexanol were screened out using multivariate statistical analysis, which were characteristic components of grassy, floral-fruity, pekoe aroma and sweet flavors. The results of the selected key characteristic volatile compounds were consistent with the sensory quantitative description. The aroma of mid-pile dried tea (MD) was exhibited a harmonious and pleasant overall flavor. This study provides a novel insight into the accumulation of volatile during the withering step of white tea production.

Adsorption and desorption characteristics of flavonoids from white tea using macroporous adsorption resin

White tea contains the highest flavonoids compared to other teas. While there have been numerous studies on the components of different tea varieties, research explicitly focusing on the flavonoid content of white tea remains scarce, making the need for a good flavonoid purification process for white tea even more important. This study compared the adsorption and desorption performance of five types of macroporous resins: D101, HP20, HPD500, DM301, and AB-8. Among the tested resins, AB-8 was selected based on its best adsorption and desorption performance to investigate the static adsorption kinetics and dynamic adsorption-desorption purification of white tea flavonoids. The optimal purification process was determined: adsorption temperature 25 °C, crude tea flavonoid extract pH 3, ethanol concentration 80 %, sample loading flow rate and eluent flow rate 1.5 BV/min, and eluent dosage 40 BV. The results indicated that the adsorption process followed pseudo-second-order kinetics. Under the above purification conditions, the purity of the total flavonoids in the purified white tea flavonoid increased from approximately 17.69 to 46.23 %, achieving a 2.61-fold improvement, indicating good purification results. The purified white tea flavonoid can be further used for nutraceutical and pharmaceutical applications.

Development and comparison of parallel reaction monitoring and data-independent acquisition methods for quantitative analysis of hydrophilic compounds in white tea

In the present work, parallel reaction monitoring (PRM) and data-independent acquisition (DIA) methods were developed for the accurate quantitation of amino acids, alkaloids nucleosides and nucleotides in tea. The quality peaks were significantly enhanced by optimizing the LC elution procedure, HCD voltage, MS resolution, and scanning event. Both methods were validated with good liner linearity (0.004-200 μg/mL), LODs (0.001-0.309 μg/mL for PRM and 0.001-0.564 μg/mL for DIA). Applied to white tea sample, the contents of these hydrophilic compounds were range from 34,655.39 to 70,586.14 mg/kg, and caffeine (32,529.02 mg/kg) and theanine (5483.46 mg/kg) were determined as the most abundant ones. Based on the quantitation data set, the white tea samples from Puer, Lincang and Xishuangbanna were clearly discriminated using multivariate data analysis. The results of the present works show that PRM and DIA have great potential in quantitative analysis of multiple hydrophilic compounds in food samples.

Another thread to uncover the aging mystery of white tea: Focusing on the natural nanoparticles in tea infusion

Aged white tea (WT) has promising medicinal potential, but how to accurately identify aged white tea is still a difficult problem. Inspired by tea cream, the relationship between the characteristics of nanoparticles in tea infusion and aging time was studied. The results showed that with the increase of aging time, the particle size of white tea nanoparticles (WTNs) decreased gradually. Microscopic images showed that the surface structure of WTNs was changed in three aspects: the waxy layer, the cuticle layer and the palisade tissue. Additional in vitro modeling demonstrated a strong correlation between nanoparticle size and protein and tea polyphenol content. The correlation between nanoparticle sizes and aging time was further verified in aged Pu'er raw tea. Starting with the tea infusion's nanoparticles, this study showed that the aging time of WT would impact the nanoparticles' properties, offering a unique way to determine the aging period of WT.

Comparative volatiles profiling in milk-flavored white tea and traditional white tea Shoumei via HS-SPME-GC-TOFMS and OAV analyses

White tea is a mildly fermented tea processed with withering and drying. Milk-flavored white tea has a unique milk flavor compared to the traditional white tea. Little is known about the aromas that make white tea taste milky. Here we conducted the volatile profiling via headspace solid-phase microextraction (HS-SPME)-gas chromatography-time-of-flight mass spectrometry (GC-TOFMS) and chemometrics to explore the key volatiles making milk-flavored white tea taste milky. Sixty-seven volatiles were identified, with 7 volatiles (OAV > 1 and VIP > 1) were characterized as the typical aromas. Green and light fruity scent volatiles, such as methyl salicylate, benzyl alcohol, and phenylethyl alcohol, were richer in TFs than MFs. Strong fruity and cheese aromas, such as dihydro-5-pentyl-2(3H)-furanone, 2-pentyl-furan, (E)-6,10-dimethyl-5,9-undecadien-2-one, and hexanal, were more abundant in MFs than TFs. Dihydro-5-pentyl-2(3H)-furanone, recognized as coconut and creamy aroma, should be the essential volatile for milky flavor. Also, (E)-6,10-dimethyl-5,9-undecadien-2-one and 2-pentyl-furan may contribute to the milk scent formation.

Validation of antioxidant, antiproliferative, and in vitro anti-rheumatoid arthritis activities of epigallo-catechin-rich bioactive fraction from Camellia sinensis var. assamica, Assam variety white tea, and its comparative evaluation with green tea fraction

The epigallocatechin-rich polyphenolic fraction of Assam variety white tea, traditionally used for the management of diverse inflammatory ailments and health drink, was investigated through eco-friendly green aqueous extraction, TLC, and HPLC characterization, phytochemical screening, in vitro DPPH assay, anti-proteinase, MTT assay on synovial fibroblast and colon cancer cells, apoptotic FACS analysis, cytokine ELISA, p-STAT3 western blotting, and in silico docking analysis. HPLC-TLC standardized white tea fraction (WT-F) rendered higher extractive-yield (21%, w/w), than green tea fraction(GT-F) (12%, w/w). WT-F containing flavonoids and non-hydrolysable polyphenols showed better antioxidant activity, rather than equivalent GT-F. WT-F demonstrated remarkable anti-rheumatoid-arthritis activity via killing of synovial fibroblast cells (66.1%), downregulation of TNF-α (93.33%), IL-6 (87.97%), and p-STAT3 inhibition (77.75%). Furthermore, WT-F demonstrated better anti-proliferative activity against colon cancer cells (HCT-116). Collectively, our study revealed that the white tea fraction has boundless potential as anti-rheumatoid arthritis and anti-proliferative agent coupled with apoptotic, antioxidant anti-proteinase, and anti-inflammatory properties. PRACTICAL APPLICATIONS: Our eco-friendly extracted bioactive aqueous fraction of white tea, characterized by TLC-HPLC study and phytochemical screening have demonstrated remarkable anti-rheumatoid arthritis property and anti-proliferative action on colon cancer cells including potential anti-oxidant, anti-inflammatory, and anti-proteinase efficacy. The test WT-F sample has shown impressive safety on normal mammalian cells. WT-F has demonstrated better efficacy against rheumatoid arthritis and cancer model compared to equivalent green tea fraction. Traditionally, it is extensively used for boosting immunity, and energy, with cosmetic, and agricultural applications by the native inhabitants. So, the aqueous fraction of WT is suggested to be used as a prophylactic nutraceutical supplement and or therapeutic agent in commercial polyherbal formulation to attenuate and management of auto-inflammatory rheumatoid arthritis and carcinogenesis of colon. It is additionally suggested to establish in vivo rheumatoid arthritis animal and clinical study to validate their pharmacokinetic stability and dose optimization coupled with anti-inflammatory, cytotoxicity, and anti-oxidant property.

White tea alleviates non-alcoholic fatty liver disease by regulating energy expenditure and lipid metabolism

Non-alcoholic fatty liver disease (NAFLD) is one of the leading causes of liver disease, which lacks effective treatments. Abnormal lipid metabolism and inflammation are the most prominent pathological manifestations of NAFLD. Recently, it has been reported that white tea extract (WTE) can regulate lipid metabolism in human adipocytes and liver cancer cells in vitro. However, its beneficial effects on NAFLD and the underlying mechanisms remain largely unknown. Here, we showed that WTE alleviated obesity, lipid accumulation, hepatic steatosis, and liver injury in a mouse model of NAFLD. Mechanistically, we demonstrated that WTE exerted the anti-NAFLD effect by decreasing the expression of genes involved in lipid transport and synthesis processes while activating genes associated with energy expenditure. In addition, a comparison of the transcriptional responses of WTE with that of green tea extract (GTE) revealed that WTE can not only regulate lipid metabolism and stress response like GTE but also regulate antioxidant and inflammatory pathways more effectively. Taken together, our findings demonstrate that WTE inhibits the progression of NAFLD in a mouse model and indicate that WTE can be a potential dietary intervention for NAFLD.

Impact of prolonged withering on phenolic compounds and antioxidant capability in white tea using LC-MS-based metabolomics and HPLC analysis: Comparison with green tea

Contents of 20 bioactive compounds in 12 teas produced in Xinyang Region were determined by high performance liquid chromatography. Ultra-high performance liquid chromatography-quadrupole time of flight-mass spectrometry was developed for untargeted metabolomics analysis. Antioxidant activities were measured by 4 various assays. Those teas could be completely divided into green and white tea through principal component analysis, hierarchical cluster analysis and orthonormal partial least squares-discriminant analysis (R²Y = 0.996 and Q² = 0.982, respectively). The prolonged withering generated 472 differentiated metabolites between white and green tea, prompted significant decreases (variable importance in the projection > 1.0, p-value < 0.05 and fold change > 1.50) of most catechins and 8 phenolic acids to form 4 theaflavins, and benefited for the accumulation of 17 flavonoids and flavonoid glycosides, 8 flavanone and their derivatives, 20 free amino acids, 12 sugars and 1 purine alkaloid. Additionally, kaempferol and taxifolin contributed to 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability of white tea.

Ameliorative effect of white tea from 50-year-old tree of Camellia sinensis L. (Theaceae) on kidney damage in diabetic mice via SIRT1/AMPK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic kidney damage (DKD) is one of the most common complications of diabetes, which is known as a chronic inflammatory kidney disease caused by persistent hyperglycemia. White tea was originally used as a folk medicine to treat measles in ancient China. What arouses our interest is that there is a traditional method to treat diabetes with white tea taken from over 30-year-old tree of Camellia sinensis L. However, there are few reports on the renal protection of white tea.

AIM OF THE STUDY

This present study was designed to study the potential protective effects of white tea (WT) and old tree white tea (OTWT) on high-fat-diet (HFD) combined with streptozotocin (STZ)-induced type 2 diabetic mice to explore the possible mechanism of WT/OTWT against DKD.

MATERIALS AND METHODS

C57BL/6 mice were randomly divided into four groups: NC, T2D, WT (400 mg/kg·b.w, p.o.), OTWT (400 mg/kg·b.w, p.o.). Diabetes was established in all groups except NC group, by six weeks of HFD feeding combined with STZ (50 mg/kg, i.p.) for 3 times, treatments were administered for six weeks and then all the animals were decapitated; kidney tissues and blood samples were collected for the further analysis, including: levels of insulin, lipid metabolism (TG, TC, HDL, LDL, FFA), antioxidative enzymes (catalase (CAT), super oxide dismutase (SOD), glutathione peroxidase (GPx)), blood urea nitrogen (BUN) and creatine, inflammatory cytokines (TNF-α, IL-1β, COX-2, iNOS, MCP-1), advanced glycation end products (AGE), receptor of AGE (RAGE), Nrf2, AMPK, SIRT1, and PGC-1α. H&E, PAS and Masson staining were performed to examine the histopathological alterations of the kidneys.

RESULTS

Our data showed that WT and OTWT reversed the abnormal serum lipids (TG, TC, HDL, LDL, FFA) in T2D mice, upregulated antioxidative enzymes levels (CAT, SOD, GPx) and inhibit the excessive production of proinflammatory mediators (including MCP-1, TNF-α, IL1β, COX-2 and iNOS) by varying degrees, and OTWT was more effective. In histopathology, OTWT could significantly alleviate the accumulation of renal AGE in T2D mice, thereby improving the structural changes of the kidneys, such as glomerular hypertrophy, glomerular basement membrane thickening and kidney FIbrosis.

CONCLUSIONS

Both WT and OTWT could alleviate the diabetic changes in T2D mice via hypoglycemic, hypolipidemic, anti-oxidative and anti-inflammatory effects, while OTWT was more evident. OTWT could prominently alleviate the accumulation of AGE in the kidneys of T2D mice, thereby ameliorating the renal oxidative stress and inflammatory damage, which was associated with the activation of SIRT1/AMPK pathway.

Effect of White Tea (Camellia sinensis) Extract on Skin Wound Healing Process in Rats

BACKGROUND

White tea (Camellia sinensis) has anti-inflammatory and antioxidant properties and a protective effect against wrinkles, sunburn and UV damages on the skin. Thus, we aimed to evaluate the effect of white tea extract on the healing process of skin wounds in rats.

METHODS

This study was done in the Research Center of Shahrekord University of Medical Sciences, Shahrekord, Iran in 2019. Excisional skin wounds were created on five groups of healthy male Wistar rats (200-250 g, n=21) including control group, Eucerin-treated group, white tea 5% ointment (Eucerin) treated group, gel-treated group, white tea 5% gel treated group. Treatment was begun on day 1 and repeated every day at the same time until day 15. Pathologic samples were taken on days 4, 7 and 15 for histopathological examinations. Kruskal-Wallis test was used to analyze data by SPSS. Statistical significance was defined as P<0.05.

RESULTS

Wound closure rate of control group was more than other groups on day 4 (P<0.05). On day 7, reepithelisation and granulation tissue of control group were more than white tea 5% ointment-treated and its inflammation was less than others (P<0.05). Neo-vascularization of white tea 5% ointment-treated group was more than control group on days 4 and 15 (P<0.05). On day 4, intact mast cells of control group were more than white tea treated groups (P<0.05). Degranulated mast cells of white tea 5% gel treated group was significantly (P<0.05) more than control group on days 4 and 15.

CONCLUSION

Five percent white tea extract could not help the skin wound healing process.

Metabolomics combined with proteomics provides a novel interpretation of the changes in nonvolatile compounds during white tea processing

In this study, metabolomics and proteomics were employed to investigate the change mechanism of nonvolatile compounds during white tea processing. A total of 99 nonvolatile compounds were identified, among which the contents of 13 free amino acids, caffeine, theaflavins, 7 nucleosides and nucleotides, and 5 flavone glycosides increased significantly, while the contents of theanine, catechins, theasinesins, 3 proanthocyanidins, and phenolic acids decreased significantly during the withering period. The results of proteomics indicated that the degradation of proteins accounted for the increase in free amino acid levels; the weakened biosynthesis, in addition to oxidation, also contributed to the decrease in flavonoid levels; the degradation of ribonucleic acids contributed to the increase in nucleoside and nucleotide levels during the withering period. In addition, the drying process was found to slightly promote the formation of white tea taste. Our study provides a novel characterization of white tea taste formation during processing.

Discrimination of white teas produced from fresh leaves with different maturity by near-infrared spectroscopy

White tea is a special tea product with increasing market demand. The assessment of white tea quality is mainly based on panel sensory by sensory evaluation experts, which is time costly and is limited by many uncertainties. This study established a rapid and accurate method for classification of white teas produced from buds and young leaves and that produced from mature leaves and shoots using near-infrared spectroscopy (NIR). Back propagation neural network modelling and support vector machine (SVM) modelling were compared with six pre-processing methods. The best performance was provided by SVM with particle swarm optimization combined with Savitzky-Golay filter pre-processing method, achieving the accuracy of 98.92% in test samples. The NIR-related chemical compounds of two categories of white teas produced from fresh leaves with different maturity were analyzed, including catechins, alkaloids, amino acids and flavonol glycosides. Compared with chemical component concentration, NIR absorbance had a distinct advantage in quick classification of white teas based on the principal components analysis. In addition, the sensory characteristics of two categories white teas produced from fresh leaves with different maturity were also assessed by panelist. The result showed that characteristics of "umami-like" and "smooth" were more likely present in white teas produced from buds and young leaves, while "woody" and "coarse" characteristics were usually present in white teas produced from mature leaves and shoots. Thus, NIR technique is a rapid and reliable method for discrimination of white teas produced from fresh leaves with different maturity, and is a potential method to discriminate sensory characteristics of white teas.

Identification and comparison of oligopeptides during withering process of White tea by ultra-high pressure liquid chromatography coupled with quadrupole-orbitrap ultra-high resolution mass spectrometry

Peptides could have specific tastes or bioactivities depending on the length and sequence of amino acids. Till date it remains unknown what peptides are formed during the white tea manufacturing process and whether they contribute to the flavor or bio-activities of white tea. As a first step to address these questions, we applied ultra-high pressure liquid chromatography coupled with quadrupole-orbitrap ultra-high resolution mass spectrometry (UPLC-Quadrupole-Orbitrap-UHRMS) to monitor peptides dynamic changes during the withering process. A total of 196 abundant peptides were identified. Most of them were oligopeptides within a molecular weight of 1000 Da. Four of them were randomly selected, synthesized peptides were applied for further confirmation and quantification. Sequence analysis suggested that some of them were potential taste contributors. Proteinase cleave site analysis identified two separate periods of active proteins degradation at 0-12 h and 30-42 h of the withering processes. Further analysis of cleavage sites also suggested that protein degradation during withering steps were random rather than a stepwise reaction.

Non-targeted metabolomics reveals distinct chemical compositions among different grades of Bai Mudan white tea

So far, the chemical quality of different grades of white tea has largely remained unexplored. The objective of this study was to establish a model for quality evaluation of different grades of Bai Mudan white tea. We applied non-targeted ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry in combination with multivariate analysis and analyzed four different grades of Bai Mudan white tea. We found that the metabolite composition from the super-grade and the first-grade shared higher similarity compared to the second-grade or the third-grade white tea, and the Partial Least Square-Discriminant Analysis model showed high capability to explain the sample variation (R2Y = 0.998, Q2 = 0.95 in negative ionization modes). In total, 93 metabolites were structurally identified, wherein 21 low abundant metabolites showed distinct changes in abundance that were closely correlated with tea grade variation. These findings suggested their potential as markers to discriminate different grades of Bai Mudan white tea.

Hydrophilic interaction liquid chromatography coupled with quadrupole-orbitrap ultra high resolution mass spectrometry to quantitate nucleobases, nucleosides, and nucleotides during white tea withering process

Nucleotides, nucleosides, and nucleobases are important bioactive compounds. Recent studies suggested that they possess taste activity. However, it remains unknown about their presence in white tea and how they change during white tea manufacture. Here, we first established method based on hydrophilic interaction liquid chromatography coupled with quadrupole-orbitrap ultra high resolution mass spectrometry (HILIC-Quadrupole-Orbitrap-UHRMS) platform, then applied it to study the dynamic changes of nucleotides, nucleosides, and nucleobases during white tea withering process. Five compounds, including adenosine 5'-monophosphate monohydrate (AMP), guanosine 5'-monophosphate disodium salt hydrate (GMP), adenosine, cytidine, thymine and uracil, were detected from withering samples. They showed a general decline trend during white tea withering process, however, considerable amount of them was retained after withering for 48 h except adenosine which was below detection limit after withering for 21 h. This study provided a complete picture about nucleotides, nucleosides and nucleobases changes during white tea withering process.

Comparison of the main compounds in Fuding white tea infusions from various tea types

The purpose of this study was to compare the main components, and particularly catechins, caffeine, theanine, free amino acids, and water extracts, in Bai Hao Yin Zhen, Bai Mu Dan, and Shou Mei Fuding white tea infusions brewed at different temperatures, and their contributions to taste were estimated by dose-over-threshold value. Infusion temperature had a distinct effect on the main components extracted, and 100 °C was found to be optimal for extracting catechins and caffeine. However, the effect of temperature on theanine, free amino acids, and water extracts varied with tea type. Bai Mu Dan and Shou Mei yielded a higher content of the major compounds than did Bai Hao Yin Zhen. Thus, infusion temperature had a large effect on extracting the main compounds, and the differences in content between the three white teas presumably reflected differences in the harvest time, processing method or leaf shape.

Application of metabolomics profiling in the analysis of metabolites and taste quality in different subtypes of white tea

Three subtypes of white tea, Silver Needle (SN), White Peony (WP), and Shou Mei (SM), differ in their taste, aroma, bioactivity, and commercial value. Here, a metabolomics investigation on the chemical compositions combining taste equivalent-quantification and dose-over-threshold (DoT) determination on the taste qualities were applied to comprehensively characterize the white tea subtypes for the first time. Significant differences in the contents of catechins, dimeric catechins, amino acids, phenolic acids, flavonol/flavone glycosides, and aroma precursors were observed among these 3 white teas. Metabolite content comparison and partial least-squares (PLS) analysis suggest that theanine, aspartic acid, asparagine, and AMP were positively correlated with the umami taste in white tea, and flavan-3-ols, theasinensins, procyanidin B3, and theobromine had positive correlations with higher bitterness and astringency tastes. In addition, puckering astringent (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG) and theogallin, bitter-tasting caffeine, and the mouth-drying/velvety-like astringent γ-aminobutyric acid (GABA) were identified as key taste compounds of white tea infusion by absolute quantification and DoT factor calculations. This work provided systematic and comprehensive knowledge on the chemical components, taste qualities, and sensory active metabolites for the subtypes of white tea.

Comparative effect of Camellia sinensis teas on object recognition test deficit and metabolic changes induced by cafeteria diet

Objectives: Consumption of high-fat and high-sugar diets in Western countries has increased significantly causing major global health problems including metabolic syndrome and obesity. In addition, studies have suggested that obesity can lead to learning and memory deficits. In this context, the use of natural compounds with low costs, minor side effects and increased antioxidant activity, such as teas, could reduce the damages induced by obesity. We investigated the effect of white, green, red, and black teas (Camellia sinensis) and their possible neuroprotective mechanisms in an experimental obesity model induced by a cafeteria diet (CD). Methods: Female Swiss mice (20-30 g) were used; they received a normal diet or a hypercaloric diet (CD) during 8 weeks. Concomitantly, some mice received orally white, green, red, or black teas (1% dose) or water. Results: The mice subjected to CD showed weight gain, body fat accumulation, increased glucose, cholesterol, and triglycerides, associated to recognition memory deficits and increased reactive species (RS) levels and acetylcholinesterase (AChE) activity in the hippocampus. All teas significantly reduced AChE activity and partially reduced fat accumulation. Green and red teas reduced memory deficit. White, green, and black teas reduced RS levels, while only green and black tea reduced plasma triglyceride levels. Discussion: According to the results obtained it is possible to conclude that green tea was better than other teas in reducing effects of the CD model, being able to protect a greater number of parameters.

Effect of brewing time and temperature on antioxidant capacity and phenols of white tea: Relationship with sensory properties

White tea is highly consumed due to its sensory properties and health benefits, although most scientific reports don't include the analysis of both properties. Therefore, the objective of the present study was to unravel the best brewing conditions for optimal extraction of the bioactive compounds and antioxidant capacity, while realising the best sensory properties. Infusions of eighty commercial teas (sold in bags or leaves) were obtained at different time-temperature ratios, studying bioactive compounds (caffeine and individual catechins), antioxidant capacity and sensory analysis. Brewing at 98 °C for 7 min was the best condition to obtain a high content of antioxidant polyphenols and pleasant sensory properties. Those teas sold in bags give rise to tea brews with almost double antioxidant capacity. In conclusion, it is very important to link sensory and chemical data to obtain optimal sensorial quality and the highest healthy properties in white tea infusions.

Characterization of white tea metabolome: Comparison against green and black tea by a nontargeted metabolomics approach

White tea is considered the least processed form of tea and is reported to have a series of potent bioactivities, such as antioxidant, anti-inflammatory, anti-mutagenic, and anti-cancer activities. However, the chemical composition of white tea and the dynamic changes of the metabolites during the manufacturing process are far from clear. In this study, we applied a nontargeted metabolomics approach based on ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) to comprehensively profile the characteristic metabolites of white tea. There were significant differences in the content of amino acids, catechins, dimeric catechins, flavonol and flavone glycosides, and aroma precursors in white tea compared with green and black teas that were manufactured from the same fresh tea leaves. Furthermore, the dynamic changes of the metabolites in the tea samples with various withering durations of 0, 4, 8, 12, 16, 20, 24, 28, and 36 h were also profiled. This study offers a comprehensive characterization of the metabolites and their changes in white tea.

Effect of water quality on the main components in Fuding white tea infusions

The aim of this study was to investigate the effect of water quality on the main components in Fuding white tea infusions, including catechins, caffeine, theanine and free amino acids. Pure, tap and spring water were tested, and water quality was found to have a distinct effect on the main compounds extracted. Pure water, which was weakly acidic and low in dissolved ions, achieved the highest catechin content, whereas caffeine and theanine, and amino acids, were higher in infusions made with spring and tap water, respectively. Sensory evaluation was performed to evaluate infusion colour, taste and aroma, and sensory quality was similarly influenced by water type, due primarily to differences in dissolved ions. Pure water was more suitable for brewing white tea with superior colour, aroma and taste.

White tea intake prevents prediabetes-induced metabolic dysfunctions in testis and epididymis preserving sperm quality

Prediabetes has been associated with alterations in male reproductive tract, especially in testis and epididymis. Moreover, in vitro studies described a promising action of tea (Camellia sinensis L.) against metabolic dysfunctions. Herein, we hypothesized that white tea (WTEA) ingestion by prediabetic animals could ameliorate the metabolic alterations induced by the disease in testicular and epididymal tissues, preserving sperm quality. WTEA infusion was prepared and its phytochemical profile was evaluated by ¹H-NMR. A streptozotocin-induced prediabetic rat model was developed and three experimental groups were defined: control, prediabetic (PreDM) and prediabetic drinking WTEA (PreDM+WTEA). Metabolic profiles of testis and epididymis were evaluated by determining the metabolites content (¹H-NMR), protein levels (western blot) and enzymatic activities of key metabolic intervenient. The quality of spermatozoa from cauda epididymis was also assessed. Prediabetes increased glucose transporter 3 protein levels and decreased lactate dehydrogenase activity in testis, resulting in a lower lactate content. WTEA ingestion led to a metabolic adaptation to restore testicular lactate content. Concerning epididymis, prediabetes decreased the protein levels of several metabolic intervenient, resulting in decreased lactate and alanine content. WTEA consumption restored most of the evidenced alterations, however, not lactate content. WTEA also improved epididymal sperm motility and restored sperm viability. Prediabetes strongly affected testicular and epididymal metabolic status and most of these alterations were restored by WTEA consumption, resulting in the improvement of sperm quality. Our results suggest that WTEA consumption can be a cost-effective strategy to improve prediabetes-induced reproductive dysfunction.

Simulated gastrointestinal digestion, intestinal permeation and plasma protein interaction of white, green, and black tea polyphenols

The gastrointestinal digestion, intestinal permeation, and plasma protein interaction of polyphenols from a single tea cultivar at different stages of processing (white, green, and black teas) were simulated. The salivary phase contained 74.8-99.5% of native polyphenols, suggesting potential bioavailability of significant amounts of antioxidants through the oral mucosal epithelium that might be gastric sensitive and/or poorly absorbed in the intestine. White tea had the highest content and provided the best intestinal bioaccessibility and bioavailability for catechins. Since most of native catechins were not absorbed, they were expected to accumulate in the intestinal lumen where a potential inhibition capacity of cellular glucose and cholesterol uptake was assumed. The permeated catechins (approximately, 2-15% of intestinal levels) significantly bound (about 37%) to plasma HDLs, suggesting a major role in cholesterol metabolism. White tea and its potential nutraceuticals could be effective in the regulation of plasma glucose and cholesterol levels.

White tea (Camellia sinensis) inhibits proliferation of the colon cancer cell line, HT-29, activates caspases and protects DNA of normal cells against oxidative damage

Tea (Camellia sinensis) is one of the most consumed beverages in the world. White tea is made from the buds and young leaves of the tea plant which are steamed and dried, whilst undergoing minimal oxidation. The MTT assay was used to test the extract on the effect of the proliferation of the colorectal cancer cell line, HT-29. The extract inhibited the proliferation of HT-29 cells with an IC50 of 87μg/ml. The extract increased the levels of caspase-3, -8, and -9 activity in the cells. DNA damage in 3T3-L1 normal cells was detected by using the comet assay. The extract protected 3T3-L1 cells against H2O2-induced DNA damage. The results from this study show that white tea has antioxidant and antiproliferative effects against cancer cells, but protect normal cells against DNA damage. Regular intake of white tea can help to maintain good health and protect the body against disease.

Phenolic content and antioxidative capacity of green and white tea extracts depending on extraction conditions and the solvent used

The efficiencies of different solvents in the extraction of phenolics from bagged and loose leaves of white and green tea, after different extraction times, as well as the antioxidative capacity of the obtained extracts, were investigated. The developed HPLC method has the potential to separate and determinate 17 phenolics widely distributed in plants, but in investigated tea extracts only four catechins and traces of three flavonols and one flavone were separated and detected based on comparison with authentic standards. The extraction efficiency of phenolics depended strongly on the time of extraction and the solvents used. The extraction of catechins from green tea was significantly affected by the form (bagged or loose) of the tea, whereas this effect was shown not to be statistically significant for white tea. Green tea was a richer source of phenolics than was white tea. The extraction of phenolics from white tea by water could be accelerated by the addition of lemon juice. Aqueous ethanol (40%) was most effective in the prolonged extraction of catechins. The antioxidative capacity of the investigated tea extracts correlated with their phenolic content.