cognitive-function

Matcha consumption leads to much higher intake of green tea phytochemicals compared to regular green tea. Previous research on caffeine, L-theanine, and epigallocatechin gallate (EGCG) repeatedly demonstrated benefits on cognitive performance.

Recent Research Papers on
cognitive-function

Production of decaffeinated green tea leaves using liquefied dimethyl ether

Author: Hideki Kanda and Peng Li and Hisao Makino

We developed a new technique for green tea decaffeination involving ingredient extraction and drying of green tea leaves by using liquefied dimethyl ether (DME) as a safe extraction solvent. After hot water extraction with water content of 74.6–76.2%, green tea leaves were tested to verify the DME extraction in both laboratory- and bench-scale processes. The distributions of caffeine and catechins in the extracted residue, organic extracts, and removed water were tested by high-performance liquid chromatography. Caffeine was completely removed from the green tea leaves. Approximately 25.2–56.0% of catechins remained in the residue after DME extraction. In particular, 56.0% of epigallocatechin gallate, which has the greatest activity of all catechins remained in the residue.

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Changes in secondary metabolites of green tea during fermentation by Aspergillus oryzae and its effect on antioxidant potential

Author: Min Ju Kim and K.M. Maria John and Jung Nam Choi and Sarah Lee and Ah Jin Kim and Young Mi Kim and Choong Hwan Lee

Metabolomic differences between green tea (GT) and Aspergillus oryzae-fermented green tea (FGT) were investigated using Liquid Chromatography–Electrospray Ionization-Ion Trap–Tandem Mass Spectrometry (LC-ESI-IT-MS/MS). To identify the metabolomic differences, principal component analysis (PCA) and orthogonal projection to latent structures discriminate analysis (OPLS-DA) of GT and FGT were performed. A total of 17 metabolites differed between GT and FGT. The major flavonoid compounds of GT, epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), decreased during fermentation, while the levels of phenolic compounds, such as gallic acid, 3-p-coumaroylquinic acid, and other flavonoid metabolites like gallocatechin, epicatechin, and epigallocatechin, increased significantly during fermentation. Notably, caffeine degradation was also observed during fermentation of GT by A. oryzae. Although the total flavonoid content of FGT decreased, the antioxidant activity of FGT increased significantly due to increased levels of other identified and unidentified metabolites. These results show that fermentation-dependent metabolomic changes have the potential to increase the bioactivity of GT.

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Effects of green tea consumption on cognitive dysfunction: An exploratory clinical study

Author: K. Ide and N. Wakamiya and M. Park and N. Takuma and S. Fujii and A. Nakahara and T. Suzuki and J. Nakase and Y. Ukawa and Y.M. Sagesaka and H. Yamada

Background: In rapidly aging societies worldwide, the number of patients with disorders marked by cognitive dysfunction, such as Alzheimer's disease, is gradually increasing; however, thus far, no fundamental curative therapy has been established. Green tea, whose major constituents are catechins and theanine, is known to have various health benefits for humans. However, the effects of green tea consumption on cognitive dysfunction remain to be clinically verified. Objective: To conduct a clinical study to investigate the effects of green tea consumption on cognitive dysfunction. Patients and methods: Twelve elderly nursing home residents (2 men, 10 women; mean age, 88 years) with cognitive dysfunction (Mini Mental State Examination [MMSE] score: <28) were recruited. Written informed consent was obtained from the patients and caregivers. The patients were asked to consume green tea powder (2 g/day [containing 227 mg of catechins and 37 g of theanine]; manufactured by ITO EN Ltd., Tokyo) for 3 months. Cognitive function was assessed by performing MMSE, and serum lipid levels were measured. Results: The MMSE scores (mean ± S.D.) significantly improved after the intervention (before intervention, 15.3 ± 7.7; after intervention, 17.0 ± 8.2; p = 0.025), especially for the category recent memory. Regarding serum lipid levels, low-density lipoprotein (LDL)-cholesterol levels remained unaltered, but triglyceride levels decreased significantly (before intervention, 124 ± 80 mg/dL; after intervention, 103 ± 57 mg/ dL; p = 0.041). Conclusion: These results suggest that green tea consumption may be effective in improving cognitive function, and additional confirmatory long-term controlled studies are needed.

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Modulation of signaling pathways in prostate cancer by green tea polyphenols

Author: Naghma Khan and Hasan Mukhtar

Prostate cancer (PCa) is the most common malignancy found in American men and the risk factors for PCa include age, family history, ethnicity, hormonal status, diet and lifestyle. For the successful development of cancer-preventive/therapeutic approaches, consumption of dietary agents capable of inhibiting or delaying the growth and proliferation of cancer cells without significantly affecting normal cells could be an effective strategy. Polyphenols derived from green tea, termed as green tea polyphenols (GTP) have received great attention in recent years for their beneficial effects, in particular, their significant involvement in cancer chemoprevention and chemotherapy. Several studies have reported beneficial effects of GTP using in vitro and in vivo approaches and in human clinical trials. Among green tea catechins, epigallocatechin-3-gallate (EGCG) is best studied for its cancer preventive properties. In this review article, we present available scientific literature about the effects of GTP and EGCG on signaling pathways in PCa.

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Stability of catechins in green tea nutraceutical products: Application of solid phase extraction–thin layer chromatography densitometry

Author: Heba-Alla H. Abd-ElSalam and Medhat A. Al-Ghobashy and Hala E. Zaazaa and Mohamed A. Ibrahim

Epigallocatechin gallate (EGCG) is a powerful antioxidant and commonly used nutraceutical. Accelerated stability of EGCG in tablet formulations was investigated. LLE and SPE were employed for sample clean-up and enrichment of EGCG over caffeine. Samples were analysed after spiking with fixed concentration of gallic acid (GA), in order to verify reproducibility of analysis. A TLC–densitometric assay was developed and validated for determination of % loss EGCG. EGCG, GA and caffeine were resolved with Rf values 0.54, 0.69 and 0.80, respectively. LC–MS/MS was used to verify identity and purity of the EGCG band. Determination was carried out over a concentration range of 0.50–5.00 μg/band and 0.20–2.40 μg/band for GA and caffeine, respectively. Results showed significant reduction in EGCG content after one, three and six months: 24.00%, 28.00% and 52.00% respectively. Results continue to demonstrate that stability of nutraceutical products should be investigated in-depth using industry-oriented protocols before granting marketing authorisation.

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Estimation of tea catechin levels using micellar electrokinetic chromatography: A quantitative approach

Author: Chao-Ming Liu and Chung-Yu Chen and Yang-Wei Lin

A simple, inexpensive micellar electrokinetic chromatography (MEKC) method with UV detection was used to determine seven catechins and one xanthine (caffeine) in tea. All the compounds were successfully separated (15 kV) within a 15-min migration period with a high number of theoretical plates (>8.0 × 10 4) in a running buffer (pH 7) containing 10 mmol l−1 sodium tetraborate, 4 mmol l−1 sodium phosphate, and 25 mmol l−1 SDS. The regression lines of all standard catechins were linear within the range of 0.03–4 μg ml−1. Green tea infused at 95 °C for 10 min showed higher levels of catechins (especially epigallocatechin galate, epicatechin gallate, and epicatechin) than tea infused at 80 °C. In addition, major differences were observed in the levels of catechins in the first and second infusions (both brewed at 95 °C for 10 min). Finally, green tea leaves were infused separately with tap water, deionised water, spring water, reverse osmosis water, and distilled water at 95 °C, and the catechin content of the infusions was investigated by the proposed method. In the infusion brewed with tap water, catechins appeared to be epimerisation from the epistructure to the nonepistructure. This epimerisation may take place more readily in tap water than in distilled water owing to the complexity of the ions present in tap water.

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Rapid tea catechins and caffeine determination by HPLC using microwave-assisted extraction and silica monolithic column

Author: A.A. Rahim and S. Nofrizal and Bahruddin Saad

A rapid reversed-phase high performance liquid chromatographic method using a monolithic column for the determination of eight catechin monomers and caffeine was developed. Using a mobile phase of water:acetonitrile:methanol (83:6:11) at a flow rate of 1.4 mL min−1, the catechins and caffeine were isocratically separated in about 7 min. The limits of detection and quantification were in the range of 0.11–0.29 and 0.33–0.87 mg L−1, respectively. Satisfactory recoveries were obtained (94.2–105.2 ± 1.8%) for all samples when spiked at three concentrations (5, 40 and 70 mg L−1). In combination with microwave-assisted extraction (MAE), the method was applied to the determination of the catechins and caffeine in eleven tea samples (6 green, 3 black and 2 oolong teas). Relatively high levels of caffeine were found in black tea, but higher levels of the catechins, especially epigallocatechin gallate (EGCG) were found in green teas.

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The characterization of caffeine and nine individual catechins in the leaves of green tea (Camellia sinensis L.) by near-infrared reflectance spectroscopy

Author: Min-Seuk Lee and Young-Sun Hwang and Jinwook Lee and Myoung-Gun Choung

Near-infrared reflectance spectroscopy (NIRS) was used to determine the contents of caffeine and nine individual catechins in tea leaves. A total of 665 samples were scanned by NIRS, and also by high performance liquid chromatography coupled to a diode array detector to determine the contents of caffeine and nine individual catechins. The calibration models for caffeine, EGC, C, EGCG, EC, ECG, and total catechins had high r2 (more than 0.90) and RSP (the ratio of standard deviation of reference data to SEP(C) in the external validation set) values (more than 4.1), indicating a good correlation between reference values and NIRS predicted values. In contrast, the calibration models of GC and EGCG-3Me had low r2 and RSP values (below 0.8 and 2.0). Therefore, these results suggest that NIRS could be applied for the rapid determination of the contents of caffeine, EGC, C, EGCG, EC, ECG, and total catechins in tea leaves for breeding programs that develop high-quality tea plants.

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Sediments in concentrated green tea during low-temperature storage

Author: Yong-Quan Xu and Gen-Sheng Chen and Qi-Zhen Du and Fei Que and Hai-Bo Yuan and Jun-Feng Yin

The formation and the main chemical components of sediments, including reversible tea sediments (RTS) and irreversible tea sediments (IRS), in concentrated green tea during low-temperature storage were studied. RTS was mainly formed in the first 10 days, and IRS was mainly formed between 20 and 40 days of storage. The RTS were the primary sediment, contributing more than 90% of the total sediment. The RTS comprised of polyphenols, total sugar, caffeine, flavones and proteins, while the IRS mainly comprised of oxalates of Ca, Mg, Ga and Mn. The total mineral content in the IRS (17.1%) was much higher than that in the RTS (2.6%) after 80 days of storage. The Ca, Mg, Mn and Ga contents in IRS were over 1.0% (w/w) each. About 75% of the IRS was soluble in 0.1 M aqueous HCl, with the oxalate accounting for 68%. Minerals and oxalic acid were the crucial factors in the IRS formation.

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Pressure-dependent kinetic modeling of solid–liquid extraction of the major green tea constituents

Author: Jun Xi and Lianggong Yan and Lang He

The main aim of this work was to model the extraction process of the major green tea constituents in order to quantify the influence of the pressure on extraction kinetics. The kinetics of solid–liquid extraction of total catechins and caffeine at several pressures (200, 300, 400 and 500 MPa) were carried out using 50% aqueous ethanol. So and Macdonald’s model involving the concept of broken and intact cells in order to describe three successive extraction periods: an initial very fast washing stage, a fast diffusion stage and a slow diffusion stage, was successfully developed for describing the mechanism of solid–liquid extraction of the major green tea constituents under different pressures. From the modeling results, the influence of the pressure on the extraction yields of total catechins and caffeine of the various stages at equilibrium, and the mass transfer coefficient were identified.

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