Research Database

Author: Kentaro Kitadate and Kohei Homma and Ashley Roberts and Takahiro Maeda

Oligonol is a functional food containing catechin-type monomers and proanthocyanidin oligomer converted from polymer forms via a novel manufacturing process. The catechin component of green tea extract has been associated with nasal toxicity in rats following subchronic exposure. To assess the potential for Oligonol to induce nasal toxicity a 13-week repeated oral dose toxicity study was conducted in rats using doses of 100, 300, and 1000 mg/kg/d. Clinical signs and mortality were not affected by Oligonol treatment. Compound-colored stools and an increase in food consumption were observed in some treated groups; however, there were no treatment-related differences in terminal body weights or with respect to the results of the gross postmortem examinations. Histopathological evaluation of the nasal cavity tissues revealed no treatment-related lesions. The results from this toxicity study indicate that Oligonol does not induce nasal toxicity and further supports the results of previous studies demonstrating the safety of Oligonol for human consumption.

 

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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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Author: Xinzhong Zhang and Fengjian Luo and Zhengyun Lou and Meiling Lu and Zongmao Chen

A novel and sensitive method for simultaneous enantiomeric analysis of two pesticides—cis-epoxiconazole and indoxacarb—in various teas, black tea infusion, and soil samples has been developed. The samples were initially subjected to acetonitrile extraction followed by cleanup using lab-made florisil/graphitized carbon black mixed solid phase extraction (SPE) column (for the different teas and soil samples) and a BondElut C18-SPE column (for the black tea infusion samples). Separation of the analytes was performed on a chiral stationary phase using high performance liquid chromatography (HPLC) under a reversed-phase isocratic elution mode followed by tandem quadrupole time-of-flight mass spectrometry (Q-TOF/MS) detection. The mobile phase components, mobile phase ratios, flow rates, column temperatures, and MS parameters were all optimized to reach high sensitivity and selectivity, good peak shape, and satisfactory resolution. The performance of the method was evaluated based on the sensitivity, linearity, accuracy, precision, and matrix effects. Under optimal conditions, for the various teas (green tea, black tea, and puer tea), fresh tea leaf, soil and black tea infusion samples spiked at low, medium, and high levels, the mean recoveries for the four enantiomers ranged from 61.0% to 129.7% with most relative standard deviations (RSDs) being 17.1% or below. Good linearity can be achieved with regression coefficients (R) of 0.9915 or above for all target enantiomers, and matrix-matched calibration concentration ranging from 5.0 to 1000 μg/L. The limits of detection (LODs) for all four target enantiomers were 1.4 μg/kg or below in the different teas and soil samples and 0.05 μg/kg or below in the black tea infusion, whereas the limits of quantification (LOQs) for those did not exceed 5.0 μg/kg and 0.2 μg/L, respectively. The proposed method is convenient and reliable and has been applied to real tea samples screening. It has also been extended for studies on the degradation kinetics and environmental behaviors in the field trials, providing additional information for reliable risk assessment of these chiral pesticides.

 

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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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Author: Jian-Hui Ye and Na-Na Li and Jian-Liang Lu and Xin-Qiang Zheng and Yue-Rong Liang

(−)-Epigallocatechin gallate (EGCg)-rich extract (EGCg > 700 mg g−1) was prepared from green tea leaves through a three-stage process consisting of liquid–liquid extraction and silica column purification. Crude tea extract was dissolved in ethyl acetate. After filtration, the solution was extracted by 10 g L−1 citric acid solution twice, and then passed through silica column. The catechins compounds in the ethyl acetate eluate were back extracted to the aqueous phase, then extracted with a mixed solution of n-hexane/ethyl acetate (2/5, v/v) 3 times, concentrated, and freeze dried. 12.8 g EGCg-rich extract containing 709 mg g−1 EGCg and 965 mg g−1 total catechins was obtained from 300 g green tea leaves, with an EGCg recovery of 26.1% and a yield of 4.3%. This method was suitable for bulk preparation of EGCg-rich catechins from green tea leaves.

 

 

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Author: R. Shahakbari and M. Eshghpour and A. Rajaei and N.M. Rezaei and P. Golfakhrabadi and A. Nejat

The objective of this study was to evaluate the effectiveness of green tea mouthwash in controlling the pain and trismus associated with acute pericoronitis in comparison to chlorhexidine (CHX) mouthwash. Ninety-seven patients with acute pericoronitis underwent debridement and received 5% green tea mouthwash (study group) or 0.12% CHX mouth rinse (control group). Pain (visual analogue scale; VAS), number of analgesics, maximum mouth opening (MMO), and number of patients with trismus were determined. There were no significant differences in demographic variables (P > 0.05), or baseline VAS (P > 0.006), MMO (P > 0.017) or number of patients with trismus (P > 0.017) between the two groups. The mean VAS score of the study group was statistically lower than that of the control group between post-treatment days 3 and 5 (P < 0.006). A significantly lower number of analgesics were taken by the study group (P < 0.05). Although the MMO of the study group was significantly lower on day 3 (P < 0.017), no significant difference was observed on day 7 (P > 0.017). Fewer of the patients rinsing with green tea had trismus on days 3 and 7, but the difference was non-significant (P > 0.017). Hence, green tea mouth rinse could be an appropriate and effective choice for the control of pain and trismus in acute pericoronitis.

 

 

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Author: Narendra Chaudhary and Jyoti Bhardwaj and Hyo Jin Seo and Min Yong Kim and Tai Sun Shin and Jong Deog Kim

Tea fruit peel is an agricultural waste of tea manufacturing industry that contains phenols with high antioxidant activities. This study examined the effect of green tea fruit peel extract (PE) against angiogenesis and obesity. We found that PE significantly inhibited the tubular formation of human umbilical vein endothelial cells (HUVECs). Epigallocatechin gallate (EGCG), epigallocatechin (EGC) and saponin were the functional components present in PE that contributed to significant anti-angiogenesis effect. Administration of PE (100 mg/kg/d) significantly decreased the body weight in rats fed high-fat diet (HFD) whereas the food intakes between HFD and PE treatment groups were not significantly different. White adipose tissue fat-pad weights were markedly reduced in rats fed HFD plus PE compared to those in HFD group. These results showed the potential of green tea fruit peel extract in preventing angiogenesis and obesity.

 

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Author: Ke-Xue Zhu and Xin Dai and Xiaona Guo and Wei Peng and Hui-Ming Zhou

Superfine green tea powder (SGTP) was premixed with organic acids (ascorbic acid, citric acid) and hydrocolloids (sodium alginate, curdlan), and then mixed with microwave-treated wheat flour to produce green tea fresh noodles (GTFN). Darken-retardant effects of organic acids, hydrocolloids and microwave treatments on GTFN were evaluated, as well as pH, polyphenol oxidase activity, sensory and microstructure characteristics. The results revealed that organic acids exhibited a suppressive effect on discoloration, among which citric acid (CA) displayed more efficient influence with lower pH. After adding hydrocolloids and microwave treatments, retardant effects exhibited more significant (P &lt; 0.05). Specifically, employing citric acid 0.6 g/100 g, sodium alginate 0.2 g/100 g, and 800 W microwave (MW) 50 s would contribute to lower darkening index ΔE* (24 h, 25 °C) at 3.88 ± 0.314, 4.94 ± 0.297, 2.78 ± 0.212, respectively. Furthermore, the combined effect of the above process restrained discoloring rate considerably (ΔE* = 1.92 ± 0.101), also provided pleasant sensory characteristics. The confocal scanning laser microscopy (CSLM) images demonstrated the microstructure of the noodle was strengthened compared with blank GTFN, and sodium alginate could serve as a binding agent to parcel SGTP and starch granules.

 

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Author: Ngoc Minh Pham and Akiko Nanri and Takeshi Kochi and Keisuke Kuwahara and Hiroko Tsuruoka and Kayo Kurotani and Shamima Akter and Isamu Kabe and Masao Sato and Hitomi Hayabuchi and Tetsuya Mizoue

Objective Higher coffee and green tea consumption has been suggested to decrease risk of type 2 diabetes, but their roles in insulin resistance (IR) and insulin secretion remain unclear. This study examined the association between habitual consumption of these beverages and markers of glucose metabolism in a Japanese working population. Materials/Methods Participants were 1440 Japanese employees (1151 men and 289 women) aged 18–69 years. Consumption of coffee and green tea was ascertained via a validated brief diet history questionnaire. Multilevel linear regression was used to estimate means (95% confidence intervals) of fasting insulin, fasting plasma glucose, homeostatic model assessment of IR (HOMA-IR), homeostatic model assessment of β-cell function (HOMA-β) and glycated hemoglobin (HbA1c) with adjustment for potential confounding variables. Results Coffee consumption was significantly, inversely associated with HOMA-IR (P for trend = 0.03), and the association appeared to be confined to overweight subjects (BMI ≥ 25 kg/m2) (P for trend = 0.01, P for interaction = 0.08). Unexpectedly, green tea consumption was positively associated with HOMA-IR (P for trend = 0.02), though there was no dose–response relationship among daily consumers of green tea. Neither coffee nor green tea consumption was associated with HOMA-β and HbA1c. Conclusions Our findings indicate that coffee consumption may be associated with decreased IR, but not with insulin secretion. The positive association between green tea consumption and IR warrants further investigation.

 

 

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Author: José Baptista and Elisabete Lima and Lisete Paiva and Ana R. Castro

“Normal-season” (bud plus first two leaves processed as commercial tea between Apr–Sep), “unused” (remaining leaves collected in Sep and Apr) and “off-season” (all leaves collected between Sep–Apr) green tea leaves samples from Camellia sinensis were extracted by water infusion followed by solvent–solvent partition to recover catechins, that were separated and quantified by HPLC methods. Total catechins content ranged between 23.72 and 73.61 mg/g of the dry weight (DW) leaves for the off-season samples and was 97.51, 115.12 and 184.62 mg/g DW for Apr, Sep and normal-season samples, respectively. The free radical scavenging activity of the off-season samples ranged between 45 and 80%, 79–90% and 90–92% for the 25, 50 and 100 ppm concentrations, respectively, after 20-min reaction time. The other samples presented values of 87%, 91% and 94% (Sep), 88%, 92% and 93% (Apr) and 89%, 93% and 95% (normal-season), using the same conditions. Total phenolics content ranged between 43.21 and 139.02 mg of gallic acid equivalents (GAE)/g DW for the off-season samples and was 182.23, 216.05 and 221.32 mg of GAE/g DW for Apr, Sep and normal-season samples, respectively. Results revealed that the unused and off-season Azorean green tea leaves (catechins-rich waste products) have potential antiradical activity that can be used for food and cosmetics preservation.

 

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