Screening of the antioxidant properties and polyphenol composition of aromatised green tea infusions

Inhibition of α-glucosidase and α-amylase by herbal compounds for the treatment of type 2 diabetes: A validation of in silico reverse docking with in vitro enzyme assays

BACKGROUND

α-Amylase and α-glucosidase are important therapeutic targets for the management of type 2 diabetes mellitus. The inhibition of these enzymes decreases postprandial hyperglycemia. In the present study, compounds found in commercially available herbs and spices were tested for their ability to inhibit α-amylase and α-glucosidase. These compounds were acetyleugenol, apigenin, cinnamic acid, eriodictyol, myrcene, piperine, and rosmarinic acid.

METHODS

The enzyme inhibitory nature of the compounds was evaluated using in silico docking analysis with Maestro software and was further confirmed by in vitro α-amylase and α-glucosidase biochemical assays.

RESULTS

The relationships between the in silico and in vitro results were well correlated; a more negative docking score was associated with a higher in vitro inhibitory activity. There was no significant (P > .05) difference between the inhibition constant (K_i ) value of acarbose, a widely prescribed α-glucosidase and α-amylase inhibitor, and those of apigenin, eriodictyol, and piperine. For α-amylase, there was no significant (P > .05) difference between the K_i value of acarbose and those of apigenin, cinnamic acid, and rosmarinic acid. The effect of the herbal compounds on cell viability was assessed with the sulforhodamine B (SRB) assay in C2C12 and HepG2 cells. Acetyleugenol, cinnamic acid, myrcene, piperine, and rosmarinic acid had similar (P > .05) IC₅₀ values to acarbose.

CONCLUSIONS

Several of the herbal compounds studied could regulate postprandial hyperglycemia. Using herbal plants has several advantages including low cost, natural origin, and easy cultivation. These compounds can easily be consumed as teas or as herbs and spices to flavor food.

LC-ESI-QTOF-MS/MS Characterisation of Phenolics in Herbal Tea Infusion and Their Antioxidant Potential

Ginger (Zingiber officinale R.), lemon (Citrus limon L.) and mint (Mentha sp.) are commonly consumed medicinal plants that have been of interest due to their health benefits and purported antioxidant capacities. This study was conducted on the premise that no previous study has been performed to elucidate the antioxidant and phenolic profile of the ginger, lemon and mint herbal tea infusion (GLMT). The aim of the study was to investigate and characterise the phenolic contents of ginger, lemon, mint and GLMT, as well as determine their antioxidant potential. Mint recorded the highest total phenolic content, TPC (14.35 ± 0.19 mg gallic acid equivalent/g) and 2,2′-azino-bis(3-e-thylbenzothiazoline-6-sulfonic acid), ABTS (24.25 ± 2.18 mg ascorbic acid equivalent/g) antioxidant activity. GLMT recorded the highest antioxidant activity in the reducing power assay, RPA (1.01 ± 0.04 mg ascorbic acid equivalent/g) and hydroxyl radical scavenging assay, •OH-RSA (0.77 ± 0.08 mg ascorbic acid equivalent/g). Correlation analysis showed that phenolic content positively correlated with the antioxidant activity. Venn diagram analysis revealed that mint contained a high proportion of exclusive phenolic compounds. Liquid chromatography coupled with electrospray ionisation and quadrupole time of flight tandem mass spectrometry (LC-ESI-QTOF-MS/MS) characterised a total of 73 phenolic compounds, out of which 11, 31 and 49 were found in ginger, lemon and mint respectively. These characterised phenolic compounds include phenolic acids (24), flavonoids (35), other phenolic compounds (9), lignans (4) and stilbene (1). High-performance liquid chromatography photometric diode array (HPLC-PDA) quantification showed that GLMT does contain a relatively high concentration of phenolic compounds. This study presented the phenolic profile and antioxidant potential of GLMT and its ingredients, which may increase the confidence in developing GLMT into functional food products or nutraceuticals.

In vitro assessment of major and trace element bioaccessibility in tea samples

Bioaccessibility of trace elements (Li, Be, Ti, Ga, Cu, Ag, Hg, Cd, Cs, Pt, Tl, Pb, As, Cr, Co, Ni, V, Se, Sn and Sb) and major elements (Rb, Ba, Al, Fe, Zn, Si, Ca, Mg, Mn, Mo, Sr, P and K) in tea infusions has been assessed using an in vitro dialyzability protocol. Gastric simulation (using pepsin solution) and intestinal simulation (using pancreatin and bile salts) were used to perform the in vitro digestion. ICP-MS, ICP-OES and FAES were used for elements determination in digested tea leaves, their infusions and the dialyzate fractions from tea infusions. Microwaves assisted acid digestion was used for the total element determination in tea leaves, while tea infusions were prepared by brewing tea leaves for 5 min in boiling water. The LODs for elements determined in tea leaves were in the range of 0.11-656 ng g^-1 and 0.02-145.6 μg g^-1 for trace and major elements, respectively. For elements' determination in tea infusions, the LODs were ranged between 0.23 and 399.9 ng L^-1 for trace elements and 0.2-1248 μg L^-1 for major elements. The LODs for the elements in the dialyzable fraction varied from 0.018 to 142 μg L^-1. The accuracy of the total element determination was evaluated using certified reference materials (Tea Leaves INCT-TL-1 and Rye Grass). The analytical recoveries were also assessed for analyzed elements in digested tea leaves (95-114%) and their infusions (92-115%), showing good recoveries. Among the studied elements, K was the most abundant element in tea leaves and tea infusions in almost all samples, followed by Ca, Mg, and P. Zn, Cs, and K showed the highest dialyzability percentages up to 84%, 76%, and 54%, respectively, followed by Si and Ca and K that show moderate to high dialyzability percentages. The accuracy of the dialysis process was evaluated using a mass-balance study.

Rapid LC-MS/MS Determination of Hesperidin in Fermented Tea Prepared from Unripe Satsuma Mandarin (Citrus unshiu) Fruits and Third-crop Green Tea (Camellia sinensis) Leaves

For improving quality control in the fermented tea production process and advancing the corresponding food labeling with function claims, a rapid and robust hesperidin analysis method using LC-MS/MS with the sample dilution approach was developed by following internationally accepted criteria of the Association of Official Analytical Chemists (AOAC). The linear correlation coefficient (r²) of the regression line was 0.9997 in the concentration range of 0.025 - 2.5 mg/L. The matrix effect evaluated using regression line slope values was negligible. The recovery rate of 100.7% indicated improved trueness. The performance of the newly developed method in determining the hesperidin content of fermented tea samples did not significantly vary from that of a well-established, conventional method. The HorRat values of intra- and inter-laboratory reproducibility studies were both within the acceptable range, indicating sufficient accuracy of the newly developed method according to the AOAC criteria.

Dose-dependent green tea effect on decrease of inflammation in human oral gingival epithelial keratinocytes: in vitro study

Objectives

This in vitro study aimed to analyze the anti-inflammatory and wound healing potential of green tea extract (GTE) in human gingival epithelial keratinocytes (HGEK) treated with lipopolysaccharides (LPS).

Materials and methods

A cell viability assay was conducted using MTT to determine nontoxic levels of GTE on immortalized HGEK. Cells were concomitantly treated with LPS (1 μg/ml) and GTE (1 mg/ml, 2.5 mg/ml, 5 mg/ml, and 10 mg/ml) to assess inflammation. Gene expression levels of inflammatory markers IL-β1, IL-6, and TNFα were measured by RT-PCR and their protein production was assessed by ELISA. The scratch wound healing assay was used to investigate the effects of different concentrations of GTE on cell migration. We also explored the effect of GTE on the induction of the Nrf2/HO-1 pathway in the cells with or without LPS.

Results

GTE at concentrations of 2.5 mg/ml, 5 mg/ml, and 10 mg/ml significantly enhanced cell viability (p < 0.05). And IL-β1, IL-6, and TNFα gene expression presented up to 10-fold decrease compared with LPS-treated cells, which was also similarly found on the protein levels. At the same concentrations, cell migration increased.

Conclusions

The mechanism results showed that GTE produced the anti-inflammatory response by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway and increasing the level of anti-oxidant protein heme oxygenase-1 (HO-1).

Clinical relevance

GTE may be potentially used as oral rinse anti-inflammatory drug for treatment and prevention of oral inflammatory diseases, which is shown here by the ability to reduce the inflammation and increase in cell migration in a dose-dependent manner.

On-line high-performance liquid chromatography coupled with biochemical detection method for screening of α-glucosidase inhibitors in green tea

An on-line high-performance liquid chromatography-biochemical detection (HPLC-BCD) method, in which compounds separated by HPLC were on-line reacted with enzyme and substrate solutions delivered by flow injection and the enzyme inhibition signal was collected by UV detection, was developed to rapidly screen α-glucosidase inhibitors from green tea extracts in this study. The chromatographic fingerprints and enzyme inhibition profiles of the different brands of green tea could be simultaneously detected by the on-line HPLC-BCD method. Enzyme inhibition profiles were detected by the UV detector at 415 nm based on the reaction of α-glucosidase and p-nitrophenyl α-d-glucopyranoside (PNPG). PNPG (1.25 mm), α-glucosidase (0.4 U/mL) and the flow rate 0.07 mL/min were applied as optimized parameters to detect α-glucosidase inhibitors in green tea. Four components in green tea showed α-glucosidase inhibition action and three of them were identified as HHDP-galloyl glucose, (-)-epigallocatechin-3-gallate and (-)-epicatechin-3-gallate by HPLC-fourier-transform mass spectrometry (HPLC-FTMS). Two brands of green tea derived from Mengding and Enshi mountainous areas might be superior to the other samples in the prevention and treatment of diabetes owing to their stronger activities of enzyme inhibitors. The proposed on-line HPLC-BCD method could be used to rapidly identify the potential enzyme inhibitors in complex matrixes.

Green tea extract attenuates LPS-induced retinal inflammation in rats

Inflammation is in a wide spectrum of retinal diseases, causing irreversible blindness and visual impairment. We have previously demonstrated that Green Tea Extract (GTE) is a potent anti-inflammatory agent for anterior uveitis. Here we investigated the anti-inflammatory effect of GTE on lipopolysaccharides (LPS)-induced retinal inflammation in rats and explored the underlying mechanism. Adult rats were injected with LPS and GTE was administered intra-gastrically at 2, 8, 26 and 32 hours post-injection. Staining of whole-mount retina showed that the number of activated microglia cells was significantly increased at 48 hours post-injection, which was suppressed after GTE treatment in a dose-dependent manner. Activation of astrocytes and Müller glia in the retina was also suppressed after GTE treatment. Meanwhile, GTE reduced the expression of pro-inflammatory cytokines including IL-1β, TNF-α and IL-6 in retina and vitreous humor. These anti-inflammatory effects were associated with a reduced phosphorylation of STAT3 and NF-κB in the retina. Furthermore, the surface receptor of EGCG, 67LR, was localized on the neurons and glia in the retina. These findings demonstrate that GTE is an effective agent in suppressing LPS-induced retinal inflammation, probably through its potent anti-oxidative property and a receptor-mediated action on transcription factors that regulate production of pro-inflammatory cytokines.

Positive and negative aspects of green coffee consumption - antioxidant activity versus mycotoxins

BACKGROUND

The quality of coffee depends not only on the contents of healthy compounds but also on its contamination with microorganisms that can produce mycotoxins during development, harvesting, preparation, transport and storage.

RESULTS

The antioxidant activity of green coffee brews measured in this study by ABTS, DPPH and Folin-Ciocalteu assays showed that coffee extracts from Robusta beans possessed higher activity in all assays than extracts from Arabica beans. The occurrence of ochratoxin A and aflatoxins (B1, B2, G1 and G2) in green coffee beans was studied using liquid chromatography/mass spectrometry. Apart from mycotoxins, the content of ergosterol as a marker indicating fungal occurrence was also determined. Among aflatoxins, aflatoxin B1 was the dominant mycotoxin in coffee bean samples, with the highest level at 17.45 ng g^-1 . Ochratoxin A was detected in four samples at levels ranging from 1.27 to 4.34 ng g^-1 , and fungi potentially producing this toxin, namely Aspergillus oryzae, Alternaria sp., Aspergillus foetidus, Aspergillus tamarii and Penicillium citrinum, were isolated.

CONCLUSION

Steaming and decaffeination of coffee beans increased antioxidant activities of brews in comparison with those prepared from unprocessed beans. Although toxins can be quantified in green coffee beans and novel fungi were isolated, their concentrations are acceptable according to legal limits. © 2017 Society of Chemical Industry.

The antioxidant effect of Green Tea Mega EGCG against electromagnetic radiation-induced oxidative stress in the hippocampus and striatum of rats

Electromagnetic radiation (EMR) of cellular phones may affect biological systems by increasing free radicals and changing the antioxidant defense systems of tissues, eventually leading to oxidative stress. Green tea has recently attracted significant attention due to its health benefits in a variety of disorders, ranging from cancer to weight loss. Thus, the aim of the present study was to investigate the effect of EMR (frequency 900 MHz modulated at 217 Hz, power density 0.02 mW/cm², SAR 1.245 W/kg) on different oxidative stress parameters in the hippocampus and striatum of adult rats. This study also extends to evaluate the therapeutic effect of green tea mega EGCG on the previous parameters in animals exposed to EMR after and during EMR exposure. The experimental animals were divided into four groups: EMR-exposed animals, animals treated with green tea mega EGCG after 2 months of EMR exposure, animals treated with green tea mega EGCG during EMR exposure and control animals. EMR exposure resulted in oxidative stress in the hippocampus and striatum as evident from the disturbances in oxidant and antioxidant parameters. Co-administration of green tea mega EGCG at the beginning of EMR exposure for 2 and 3 months had more beneficial effect against EMR-induced oxidative stress than oral administration of green tea mega EGCG after 2 months of exposure. This recommends the use of green tea before any stressor to attenuate the state of oxidative stress and stimulate the antioxidant mechanism of the brain.

Location and Effects of an Antitumoral Catechin on the Structural Properties of Phosphatidylethanolamine Membranes

Green tea catechins exhibit high diversity of biological effects including antioncogenic properties, and there is enormous interest in their potential use in the treatment of a number of pathologies. It is recognized that the mechanism underlying the activity of catechins relay in part in processes related to the membrane, and many studies revealed that the ability of catechins to interact with lipids plays a probably necessary role in their mechanism of action. We present in this work the characterization of the interaction between an antitumoral synthetically modified catechin (3-O-(3,4,5-trimethoxybenzoyl)-(-)-catechin, TMCG) and dimiristoylphosphatidyl-ethanolamine (DMPE) membranes using an array of biophysical techniques which include differential scanning calorimetry, X-ray diffraction, infrared spectroscopy, atomic force microscopy, and molecular dynamics simulations. We found that TMCG incorporate into DMPE bilayers perturbing the thermotropic transition from the gel to the fluid state forming enriched domains which separated into different gel phases. TMCG does not influence the overall bilayer assembly of phosphatidylethanolamine systems but it manages to influence the interfacial region of the membrane and slightly decrease the interlamellar repeat distance of the bilayer. TMCG seems to be located in the interior of the phosphatidylethanolamine bilayer with the methoxy groups being in the deepest position and some portion of the molecule interacting with the water interface. We believe that the reported interactions are significant not only from the point of view of the known antitumoral effect of TMCG, but also might contribute to understanding the basic molecular mechanism of the biological effects of the catechins found at the membrane level.

Antioxidant, anti-inflammatory and anticarcinogenic activities of edible red oak (Quercus spp.) infusions in rat colon carcinogenesis induced by 1,2-dimethylhydrazine

Red oak (Quercus spp.) leaves are traditionally used as food in Mexico, and some of their infusions have potential anticarcinogenic and anti-inflammatory effects; however, these properties have not yet been scientifically tested. The aim of this work was to explore the anti-inflammatory activity in HT-29 cells and anticarcinogenic effect in 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis of red oak infusions. Quercus infusions were prepared and administered as the sole source of drink to male Sprague-Dawley rats (1% w/v) for the entire 26-week experimental period. On week 4, rats received 8 subcutaneous injections of DMH (21 mg/kg body weight) once a week. The results showed that mean tumor (0.9 ± 0.2 vs. 2.6 ± 0.3) and multiplicity (1.2 ± 0.1 vs. 2.0 ± 0.23), and β-catenin protein level (2.2-fold) in adenocarcinomas were significantly lower in Quercus  sideroxyla-treated group compared with DMH group. By contrast, Quercus  durifolia and Quercus  eduardii infusions had no protective effect. Additionally, the experiments in HT-29 cells confirmed that Q. sideroxyla infusion effectively decreased the levels of the inflammatory markers COX-2 and IL-8 by modulating the expression of NF-κB. These results highlight some of the molecular mechanisms related to the chemopreventive effect of Q. sideroxyla infusion and its potential value as a source of bioactive compounds.

Green Tea Extract (GTE) improves differentiation in human osteoblasts during oxidative stress

Background

Oxidative stress is involved in the pathogenesis of bone diseases such as osteoporosis, which has a high coincidence with fractures in elderly. Several studies showed positive effects of herbal bioactive substances on oxidative stress. This study analyses the effect of green tea extract (GTE) Sunphenon 90LB on primary human osteoblasts differentiation and viability during H₂O₂-induced oxidative stress. Moreover, it was analyzed, whether GTE acts during the HO-1 signaling pathway.

Methods

Human osteoblasts were isolated from femoral heads of patients undergoing total hip replacement. Beneficial effects of GTE on osteoblasts were examined in a dose- and time-dependent manner. Furthermore, GTE was given before, simultaneous with and after induction of oxidative stress with 1 mM H₂O₂ to simulate prophylactic, acute and therapeutic use, respectively. Cell damage was measured by LDH leakage and cell viability by MTT assay. Flow cytometry was applied to measure formation of Reactive Oxygen Species by using 2`7`-dichlorofluorescein-diacetate. The formation of Extracellular Matrix after differentiation with GTE supplementation during oxidative stress was visualized with von Kossa and Alizarin Red staining. Last one was additionally photometrically quantified. To assess the effects of H₂O₂ and GTE on the osteogenic genes, RT-PCR was performed. To evaluate the intramolecular influence of GTE after the stimulation the protein levels of HO-1 were analyzed.

Results

Stimulation of primary human osteoblasts with low doses of GTE during oxidative stress over 21 days improved mineralization. Furthermore, GTE supplementation in combination with H₂O₂ leads to a higher gene expression of osteocalcin and collagen1α1 during osteoblasts differentiation. Both are important for bone quality. Pre-incubation, co-incubation and post-incubation of osteoblasts with high doses of GTE protect the osteoblasts against acute oxidative stress as shown by increased cell viability, decreased LDH leakage, and reduced production of intracellular free radicals. Functional analysis revealed an increased HO-1 protein synthesis after stimulation with GTE.

Conclusions

Incubation of human primary osteoblasts with GTE significantly reduces oxidative stress and improves cell viability. GTE also has a beneficial effect on ECM production which might improve the bone quality. Our findings suggest that dietary supplementation of GTE might reduce inflammatory events in bone-associated diseases such as osteoporosis.

Qualidade funcional da infusão do chá verde comercial

OBJETIVO: O objetivo deste trabalho foi avaliar a qualidade de duas marcas comerciais de chá verde em sachê, e verificar o efeito do tempo de infusão, em intervalos de tempos que incluem o recomendado pelo fabricante, sobre a disponibilidade dos compostos funcionais. MÉTODOS: Por análises em cromatografia líquida ultrarrápida com detector de arranjos de díodo,foram identificadas e quantificadas a cafeína, a catequina, a epigalocatequina, a rutina e a epicatequina. RESULTADOS: A epigalotocatequina e a catequina foram encontradas em maior concentração no tempo seis minutos de infusão em água (100°C) em ambas as marcas, sendo a rutina apenas encontrada na infusão por seis minutos e em apenas uma das marcas avaliadas. A extraçãocom metanol (99,8%) aumentou significativamente o rendimento de todos os compostos avaliados. Foi observado que atividade antioxidante equivalente ao trolox do chá aumentou diretamente com o aumento do tempo de infusão, no entanto, para os extratos obtidos em metanol, a atividade antioxidante foi menor que todos os outros tratamentos, havendo diferença significativa (p<0,05). CONCLUSÃO: As análises químicas de umidade, cinzas e cinzas insolúveis em ácido clorídrico revelaram que as duas marcas avaliadas estão em conformidade com a legislação para esses parâmetros, bem como com relação à presença de sujidades e materiais estranhos, revelados na microscopia.