Medicinal and therapeutic potentialities of tea (Camellia sinensis L.) – A review

Antiviral activity of theaflavin digallate against herpes simplex virus type 1

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Black tea theaflavins show significant anti-herpes simplex virus type 1 (HSV-1) effect on both A549 and Vero cells.

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Theaflavin is able to inhibit the entry of HSV-1 to its host by blocking the adsorption and penetration processes.

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Application of these agents as natural topical remedy to prevent and treat HSV-1 infection and spreading is promising.

Tea is the second most consumed drink in the world. The beneficial effects of tea have been mostly attributed to its catechin content. Black tea is derived from the leaves of Camellia sinensis plant, and it is rich in theaflavin polyphenols, in particular theaflavin (TF1), theaflavin-3-monogallate (TF2A), theaflavin-3′-monogallate (TF2B), and theaflavin-3,3′-digallate (TF3). Vero and A549 cells were used to evaluate the effect of purified individual black tea theaflavins as anti-herpes simplex virus 1 agents. With the rise of HSV resistant strains, there is a critical need to develop novel antiherpesviral treatments. Results of the cytotoxicity assay tested by MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium] showed that TF1, TF2, and TF3 are not toxic to Vero and A549 cells at a concentration up to 75 μM. The antiviral activity of the individual theaflavins was tested by plaque reduction assay, MTS assay, flow cytometric analysis and confocal microscopy observations. The results showed that TF1, TF2, and TF3 exhibit potent, dose-dependent anti-HSV-1 effect, with TF3 being the most efficient in both Vero and A549 cells. A concentration of 50 μM TF3 and above was sufficient to inhibit >99% of the production of HSV-1 viral particles. The anti-HSV-1 effect of TF3 is due to a direct effect on the virions, and treating Vero or A549 cells with TF3 for 1 h prior to infection, or treating the cells at different times post infection does not inhibit HSV-1 production. TF3 is stable at vaginal pH, indicating its potential to be a promising natural and affordable remedy against herpes simplex viral infections.

Anticancer effect of black tea extract in human cancer cell lines

In this study we investigated effects of natural extract from the black tea Camellia sinensis (BTE) against human colon carcinoma cell line HT-29, human breast carcinoma cell line MCF-7, human alveolar carcinoma cell line A549 and healthy cell line NIH-3T3. We identified concentration range for cytotoxic/antiproliferative effects using MTT assay and the trypan blue assay, gel electrophoresis we employed to determine the type of cell death induced by BTE and DNA damage we determined by comet assay. Different concentrations of the extract (0.00078 - 5 μg/mL) we added to the cultured cells and incubated for 216 h. BTE showed cytotoxic effects against all carcinoma cell lines, however HT-29 and MCF-7 cells were more sensitive than A549. BTE showed no antiproliferative effect against healthy cells NIH-3T3 at tested concentrations. We found no apoptotic cell death in HT-29 and MCF-7 cells after 72 h of incubation in case of single administration of BTE but in case of repetitive administration of BTE (BTE was added to the cells each day) we found apoptotic cell death in HT-29 after 72 h incubation. BTE induced also DNA strand breaks and oxidative damage to DNA in carcinoma cells HT-29 and MCF-7.

Green tea and glycine aid in the recovery of tendinitis of the Achilles tendon of rats

PURPOSE

Green tea (GT) is widely used due to its anti-inflammatory properties. Previous studies have shown beneficial effects of a glycine diet on the remodeling process in inflamed tendons. Tendinitis is commonly observed in athletes and is of concern to surgeons due to the slowness of the recovery process. Our hypothesis is that GT + a glycine diet may improve tendinitis.

AIM OF THE STUDY

To analyze the effect of GT and/or glycine in the diet on tendinitis.

MATERIALS AND METHODS

Wistar rats were divided into seven groups (G): control group (C); G1 and G4, tendinitis; G2 and G5, tendinitis supplied with GT; and G3 and G6, tendinitis supplied with GT and a glycine diet for 7 or 21 days, respectively. We performed zymography for metalloproteinase, biochemical, morphological and biomechanics tests.

RESULTS

G2, G3 and G5 showed high levels of hydroxyproline in relation to G1, while G4 showed high levels of glycosaminoglycans. High activity of metalloproteinase-2 was detected in G3. The organization of collagen bundles was better in G2 and G3. G5 showed similar birefringence measurements compared with C. G5 withstood a larger load compared with G4.

CONCLUSIONS

The presence of metalloproteinase-2 indicates that a tissue is undergoing a remodeling process. High birefringence suggests a better organization of collagen bundles. After 21 days, G5 sustained a high load before rupture, unlike G4. The results suggest that GT + a glycine diet has beneficial effects that aid in the recovery process of the tendon after tendinitis.

Effect of pH and metal ions on DPPH radical scavenging activity of tea

The 2,2'-diphenyl-1-picrylhydrazyl (DPPH) assay is commonly applied for the estimation of antioxidant activity of plant extracts. This article discusses the effect of a sample pH and the presence of metal ions on the results obtained using DPPH method for several tea infusions. Higher radical quenching was observed in less acidic media. The impact of metal ions depends of the types of metal ion and its concentration. Quercetin and epigallocatechin gallate were less efficient in the reaction with DPPH in the presence of Al(III). Desalting process using cation-exchange resin Dowex 50Wx8 decreased the content of metal ions in all studied tea infusions. The DPPH scavenging activity of the effluents after this process were higher than those of the primary extracts and this may be related to the actual antioxidant capacity of these samples.

Modelling Extraction of White Tea Polyphenols: The Influence of Temperature and Ethanol Concentration

The optimization of the extraction of natural antioxidants from white tea has fostered intensive research. This study has investigated the effects of ethanol-water mixtures, temperature and time on the extraction of polyphenols and antioxidant components from white tea. The response surface methodology was applied to identify the best extraction conditions. The best conditions to maximize the extraction of total polyphenols were: ethanol, 50%, for 47.5 min. Although the yield of polyphenols was optimal at 65 °C, the maximum antioxidant capacity was achieved with an extraction temperature of 90 °C. This study has identified the optimal conditions for the extraction of tea liquor with the best antioxidant properties. Epigallocatechin gallate, epicatechin gallate, epigallocatechin and epicatechin were extracted from white tea at concentrations up to 29.6 ± 10.6, 5.40 ± 2.09, 5.04 ± 0.20 and 2.48 ± 1.10 mg/100 g.

Antioxidant and antiangiogenic properties of phenolic extract from Pleurotus tuber-regium

Pleurotus tuber-regium (Fries) Singer (PTR), both an edible and a medicinal mushroom also known as tiger milk mushroom, has experienced growing popularity and economic importance due to its flavor, nutritive value, and medicinal effects. In this study, the antioxidant and antiangiogenic activities of a 60% ethanol extract (EE) obtained from the sclerotium of PTR were investigated. Typical phenolic compounds including protocatechuic, chlorogenic, syringic, ferulic, and folic acid were identified and quantified in EE by the HPLC-UV-ESI/MS analyses. EE possessed strong antioxidant activity and could dose-dependently inhibit vascular endothelial growth factor (VEGF)-induced human umbilical vein endothelial cells (HUVEC) migration and tube formation. qPCR results showed that VEGF-induced FGF, ANG-Tie, and MMP gene expression as well as VEGFR were down-regulated at the mRNA level after treated with EE, suggesting that multiple molecular targets related to angiogenesis was involved. Furthermore, EE also inhibited the formation of subintestinal vessel plexus (SIVs) in zebrafish embryos in vivo. All of these suggested that EE of PTR could be the source of potential inhibitors to target angiogenesis.

Black tea polyphenols: a mechanistic treatise

Dietary interventions are among the emerging trends to curtail physiological malfunctioning like cancer, diabetes, cardiac complications, etc. The essence of phytonutrients has developed the concept of nutraceuticals at the junction of diet health linkages. In this context, theaflavin & thearubigins are the oxidized derivatives of black tea catechins during fermentation having nutraceutical potential owing to esterification of hydroxyl ring with digallate esters. Theaflavin may influence activation of transcription factors such as NFnB or AP-1 that ultimately hinder the formation of nitric oxide expression gene. Likewise, black tea contains a unique amino acid theanine acts as neurotransmitter owing to its ability to cross the blood-brain barrier. Moreover, it boasts immunity by enhancing the disease-fighting ability of gamma delta T cells. Theaflavin & thearubigins act as safeguard against oxidative stress thereby effective in the cardiac functioning. The mechanistic approach of these antioxidants is likely to be associated with inhibition of redox sensitive transcription factors & pro-oxidant enzymes such as xanthine oxidase or nitric oxide synthase. However, their involvement in antioxidative enzyme induction as in glutathione-S-transferases is also well documented. They act as curative agent against numerous pathological disorders by disrupting the electron chain thus inhibiting the progression of certain ailments. Black tea polyphenols established themselves as strong antioxidants due to their standard one-electron potential, and their vitality is dependent on the concentration of polyphenols and pH for their inclusive execution. Present review is an attempt to enrich the readers regarding the health promoting aspects of black tea polyphenols. Concomitantly, it needs core attention of researchers for the exploitations of black tea flavanols as an important dietary constituent for the vulnerable segment.

Traditional Chinese herbs as chemical resource library for drug discovery of anti-infective and anti-inflammatory

ETHNOPHARMACOLOGICAL RELEVANCE

Infection is a major group of diseases which caused significant mortality and morbidity worldwide. Traditional Chinese herbs have been used to treat infective diseases for thousands years. The numerous clinical practices in disease therapy make it a large chemical resource library for drug discovery.

MATERIALS AND METHODS

In this study, we collected 1156 kinds of herbs and 22,172 traditional Chinese medicinal compounds (Tcmcs). The chemical informatics and network pharmacology were employed to analyze the anti-infective effects of herbs and Tcmcs. In order to evaluate the drug likeness of Tcmcs, the molecular descriptors of Tcmcs and FDA-approved drugs were calculated and the chemical space was constructed on the basis of principal component analysis in the eight descriptors. On purpose to estimate the effects of Tcmcs to the targets of FDA-approved anti-infective or anti-inflammatory drugs, the molecular docking was employed. After that, docking score weighted predictive models were used to predict the anti-infective or anti-inflammatory efficacy of herbs.

RESULTS

The distribution of herbs in the phylogenetic tree showed that most herbs were distributed in family of Asteraceae, Fabaceae and Lamiaceae. Tcmcs were well coincide with drugs in chemical space, which indicated that most Tcmcs had good drug-likeness. The predictive models obtained good specificity and sensitivity with the AUC values above 0.8. At last, 389 kinds of herbs were obtained which were distributed in 100 families, by using the optimal cutoff values in ROC curves. These 389 herbs were widely used in China for treatment of infection and inflammation.

CONCLUSION

Traditional Chinese herbs have a considerable number of drug-like natural products and predicted activities to the targets of approved drugs, which would give us an opportunity to use these herbs as a chemical resource library for drug discovery of anti-infective and anti-inflammatory.

Gastroprotective bio-guiding fractionation of hydro-alcoholic extracts from green- and black-teas (Camellia sinensis)

Hydro-alcoholic extracts from leaves of Camellia sinensis (green- and black-tea leaves) were submitted to a fractionation, promoting the compound separation according to their polarity, and analyzed by ultra-high performance liquid chromatography-mass spectrometry. A wide range of compounds could be identified, such as catechins and their gallate (esters) or oxidation derivatives (theaflavins), glycosylated flavonoids and other phenolics, as well as lipids, saponins and alkaloids. Also have been developed, via bio-guided examination, the gastroprotective property of the compounds identified. The samples were assayed using the model of acute gastric lesions induced in rats by ethanol. Hydro-alcoholic extracts of green-tea and black-tea protected the gastric mucosa with ED₅₀=3.6 and 10.2mg/kg, respectively, with participation of gastric mucus and reduced glutathione (GSH). The ethyl acetate fraction from green-tea and aqueous fraction from black-tea were, respectively, 6 and 10 times more effectiveness than the initial extracts. Moreover, the epigallocatechin gallate (EGCG, 0.204mg/kg), a main component of ethyl acetate fraction from green tea, reduced the gastric lesion by 56% and restored the mucus levels, however the rutin (0.0133mg/kg), a flavonoid found in the most active fraction of black-tea, was less significant at the natural concentrations. These results have confirmed that the different compounds present in green- and black-tea hydro-alcoholic extracts and partitioned fractions produce relevant gastroprotection mainly via maintenance of the protective factors, mucus and GSH.

Radical scavenging of white tea and its flavonoid constituents by electron paramagnetic resonance (EPR) spectroscopy

White tea (WT) presents high levels of catechins, which are known to reduce oxidative stress. WT is the least processed tea, unfermented and prepared only from very young tea leaves. The subject of this paper is the use of the spin trap method and electron paramagnetic resonance (EPR) spectroscopy as the analytical tool to measure, for the first time, the radical scavenging activity of WT and its major catechin components, epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG), against the methoxy radical, using ferulic acid as antioxidant pattern. The antioxidant activity has been measured by the decrease of the intensity of the spectral bands of the adduct DMPO-OCH3 in the EPR with the amount of antioxidant in the reactive mixture. Tea leaves and buds were extracted with waterless methanol. It has been proved that tea compounds with more antiradical activity against methoxy radical are those with the gallate group, EGCG and ECG.

Effects of fertilizing with N, p, se, and zn on regulating the element and functional component contents and antioxidant activity of tea leaves planted in red soil

New fertilizing strategies (with exogenetic N, P, Se, and Zn) were explored to regulate the element (Se, Zn, Mn, and Al) and functional component (polyphenol, catechins, free amino acid, polysaccharide, and caffeine) contents of new (a bud and two leaves, grown for about 10 days) and old tea leaves (grown for >3 months) cultivated in a hilly red soil region. Using four different fertilizing strategies (A, Se + Zn; B, Se + Zn + N; C, Se + Zn + P; D, Se + Zn + N + P), the Al and Mn contents of tea leaves in both new and old leaves were significantly decreased. Meanwhile, the contents of Se and Zn were increased, and the contents of some functional components as well as the antioxidant activities in tea leaves were improved. In particular, fertilizing strategy C showed the highest Se (0.444 μg/kg), total polyphenol (28.294%), and catechins (131.852 mg/g) contents and antioxidant activities (DPPH, 95.06%; FRAP, 3.81 mmol FeSO4/g; reducing power, 1.26) as well as the lowest Al (222.005 mg/kg) content among these four strategies, whereas fertilizing strategy B showed the highest Zn (34.235 mg/kg), total free amino acid (5.60%), tea polysaccharide (5.79%), and caffeine (56.684 mg/g) contents as well as the lowest Mn content (747.658 mg/kg). It has been proven that exogenetic elements (N, P, Se, and Zn) as fertilizers could be an effective way to produce tea leaves with higher Se, Zn, and functional component contents and antioxidant activity as well as lower Al and Mn contents in a red soil region.

White tea as a promising antioxidant medium additive for sperm storage at room temperature: a comparative study with green tea

Storage of sperm under refrigeration reduces its viability, due to oxidative unbalance. Unfermented teas present high levels of catechin derivatives, known to reduce oxidative stress. This study investigated the effect of white tea (WTEA) on epididymal spermatozoa survival at room temperature (RT), using green tea (GTEA) for comparative purposes. The chemical profiles of WTEA and GTEA aqueous extracts were evaluated by (1)H NMR. (-)-Epigallocatechin-3-gallate was the most abundant catechin, being twice as abundant in WTEA extract. The antioxidant power of storage media was evaluated. Spermatozoa antioxidant potential, lipid peroxidation, and viability were assessed. The media antioxidant potential increased the most with WTEA supplementation, which was concomitant with the highest increase in sperm antioxidant potential and lipid peroxidation decrease. WTEA supplementation restored spermatozoa viability to values similar to those obtained at collection time. These findings provide evidence that WTEA extract is an excellent media additive for RT sperm storage, to facilitate transport and avoid the deleterious effects of refrigeration.

Effect of white tea (Camellia sinensis (L.)) extract in the glycolytic profile of Sertoli cell

PURPOSE

Many health benefits have been attributed to tea (Camellia sinensis (L.)), and tea infusions are used as dietary agent and included in food supplements. Herein, we report the effect of a white tea (WTEA) extract in Sertoli cell (SC) metabolism. The SC is responsible for the nutritional support of the developing germ cells.

METHODS

An aqueous WTEA extract was prepared and analyzed by (1)H-NMR. Rat SCs were cultured with or without the WTEA extract. mRNA and protein levels of glucose transporters (GLUT1 and GLUT3), phosphofructokinase, lactate dehydrogenase (LDH) and monocarboxylate transporter 4 were determined by qPCR and western blot. LDH activity was assessed and metabolite production/consumption determined by (1)H-NMR.

RESULTS

WTEA-exposed SCs presented decreased protein and mRNA levels of GLUT1 and decreased glucose uptake. However, intracellular LDH activity was increased and SC lactate production was stimulated by the presence of the WTEA extract. Interestingly, alanine production was also found to be stimulated in WTEA extract-exposed SCs.

CONCLUSION

WTEA extract altered the glycolytic profile of cultured SCs, stimulating lactate production. Since lactate is used as metabolic substrate and has an anti-apoptotic effect in the developing germ cells, the supplementation with WTEA extract may be advantageous to improve male reproductive health.

Epigallocatechin-3-gallate inhibits hepatoblastoma growth by reactivating the Wnt inhibitor SFRP1

Activation of Wnt signaling plays a central role in the formation of hepatoblastoma (HB), the most common pediatric liver cancer. Blocking this pathway with specific inhibitors is currently the target of various research endeavours. This study provides evidence that the naturally occurring flavonoid epigallocatechin-3-gallate (EGCG) is highly effective against HB growth through inhibition of Wnt signaling. We demonstrate that EGCG has a strong cytotoxic effect on HB cells in a time- and dose-dependent manner by impinging on cell viability, while leaving normal fibroblasts unaffected. Apoptotic features, including morphological changes, caspase 3 activity, and proteolytic cleavage of poly(ADP-ribose) polymerase, were frequently found in EGCG-treated HB cells, thereby suggesting involvement of the mitochondrial intrinsic apoptotic pathway. We furthermore show that EGCG effectively inhibits Wnt signaling, as evidenced by down-regulation of Wnt-responsive reporter gene activity and expression of the Wnt target genes MYC and CCND1. Interestingly, EGCG induced reexpression of the tumor suppressor gene SFRP1, which is transcriptionally silenced in HB cells and known to down-regulate Wnt signaling. Considering the lack of toxic effects on normal cells, EGCG should be preclinically validated as an adjuvant therapy in vivo with the ultimate goal of determining its efficacy in human trials.

Regulatory T-cell modulation by green tea in chronic lymphocytic leukemia

Regulatory T cells (Tregs) are considered to be key immunomodulatory cells of the immune system and are increased in chronic lymphocytic leukemia (CLL). Rai stage 0 identifies patients with early stage CLL for which there is no effective intervention at the present time and a "wait and see" policy is usually adopted. Some biological and clinical studies have reported that green tea constituents, such as epigallocatechin-gallate (EGCG), have antitumor effects on hematologic malignancies including CLL. We report data on a clinical trial in which green tea extracts were given orally to 12 patients with stage 0 CLL and 12 healthy subjects. Ten patients and 10 controls completed the 6-month scheduled therapy. Two patients and 2 controls stopped therapy within 1 month because of tachycardia and epigastralgia. Eight out 10 evaluable patients (80 percent) showed a reduction of lymphocytosis and absolute number of circulating Tregs, as well. One patient (10 percent) had a stabilization of lymphocytosis and a reduction of Tregs, and 1 patient (10 percent) showed an increase of both lymphocytosis and Tregs. Only the non-responding patient progressed after 5 months from the end of green tea administration and chemotherapy was given. Interestingly, both IL-10 and TGF-beta serum levels declined throughout the green tea intake period, in both patients and controls. These data seem to indicate that green tea is able to modulate circulating Tregs in CLL patients with early stage of the disease. This can result in the control of lymphocytosis as well as in the prevention of disease progression.

Effects of water solutions on extracting green tea leaves

This study investigates the effects of water solutions on the antioxidant content of green tea leaf extracts. Green teas prepared with tap water and distilled water were compared with respect to four antioxidant assays: total phenol content, reducing power, DMPD assay, and trolox equivalent antioxidant capacity assay. The results indicate that green tea prepared with distilled water exhibits higher antioxidant activity than that made with tap water. The high performance liquid chromatography showed that major constituents of green tea were found in higher concentrations in tea made with distilled water than in that made with tap water. This could be due to less calcium fixation in leaves and small water clusters. Water solutions composed of less mineralisation are more effective in promoting the quality of green tea leaf extracts.

Antimutagenic activity and preventive effect of black tea on buccal mucosa cancer

A black tea product was evaluated for anti-mutagenic and in vivo anticancer effects. At concentrations of 1.25 and 2.5 mg/plate, black tea exhibited anti-mutagenicity with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) in the Salmonella typhimurium TA100 strain. A Kunming (KM) mouse buccal mucosa cancer model was established by injecting mice with U14 squamous cell carcinoma cells. Following injection, the wound at the injection site was smeared with black tea. It was observed that the tumor volumes for the groups treated with different concentrations of black tea were smaller than the control groups. The sections of buccal mucosa cancer tissue showed that cancer development in the black tea groups was weaker compared with that in the control group. Similar results were observed in the lesion section of the cervical lymph. Using reverse transcription polymerase chain reaction (RT-PCR), the black tea groups demonstrated an increase in Bcl-2-associated X protein (Bax) and a decrease in B cell lymphoma-2 (Bcl-2) expression, compared with the control groups. The results demonstrated that black tea had an improved antimutagenic effect and in vivo buccal mucosa cancer preventive activity compared with the untreated control in mice.

Hypoglycemic Effect of Bumelia sartorum Polyphenolic Rich Extracts

Bumelia sartorum (Sapotaceae) is used ethnomedicinally for treatment of several diseases, including diabetes mellitus. The aim of this work was to investigate the hypoglycemic effect of B. sartorum extracts, rich in polyphenolic compounds, and the possible mechanisms of action. Assessment of B. sartorum hypoglycemic activity was performed from the blood glucose level in normoglycemic mice after administration of the extract by oral gavage. The hypothesis that sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) inhibition could prolong the increase in cytoplasmic Ca2+ concentration, thus leading to an increase of insulin release was evaluated. The enzyme inhibition was measured by ATP hydrolysis using SERCA1 isolated from rabbit skeletal muscle. The total content of phenolic compounds was determined by the Folin-Ciocalteau method. The ethyl acetate (EtOAc) partition and F5 fraction obtained from B. sartorum, both of them rich in polyphenolics, were shown to have a hypoglycemic effect on normoglycemic mice, more significant than that of the known antidiabetic drug, glibenclamide used as a standard comparable compound. Both samples significantly inhibited SERCA activity. Different extracts of B. sartorum, rich in polyphenolic compounds, were able to reduce blood glucose in normoglycemic mice and inhibit SERCA activity. SERCA inhibition may be one of the possible mechanisms involved in glucose decrease.

Inhibition of herpes simplex virus type 1 with the modified green tea polyphenol palmitoyl-epigallocatechin gallate

Green tea polyphenol epigallocatechin gallate (EGCG) is a strong antioxidant that has previously been shown to reduce the number of plaques in HIV-infected cultured cells. Modified EGCG, palmitoyl-EGCG (p-EGCG), is of interest as a topical antiviral agent for herpes simplex virus (HSV-1) infections. This study evaluated the effect of p-EGCG on HSV-infected Vero cells. Results of cell viability and cell proliferation assays indicate that p-EGCG is not toxic to cultured Vero cells and show that modification of the green tea polyphenol epigallocatechin gallate (EGCG) with palmitate increases the effectiveness of EGCG as an antiviral agent. Furthermore, p-EGCG is a more potent inhibitor of herpes simplex virus 1 (HSV-1) than EGCG and can be topically applied to skin, one of the primary tissues infected by HSV. Viral binding assay, plaque forming assay, PCR, real-time PCR, and fluorescence microscopy were used to demonstrate that p-EGCG concentrations of 50 μM and higher block the production of infectious HSV-1 particles. p-EGCG was found to inhibit HSV-1 adsorption to Vero cells. Thus, p-EGCG may provide a novel treatment for HSV-1 infections.

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

BACKGROUND

Aromatised green teas are widely sold and popular owing to their fragrance. In this study the antioxidant activity of six commercial green tea infusions was assessed by three complementary assays.

RESULTS

In order to evaluate the tea infusions as antioxidant sources, their phenolic content (Folin-Ciocalteu assay), cupric ion-reducing antioxidant capacity (CUPRAC) and 2,2-diphenyl-1-picryhydrazyl (DPPH) radical-scavenging ability were determined. Their content of polyphenols was also determined by high-performance liquid chromatography/mass spectrometry (HPLC/MS) in negative electrospray ionisation mode. Some teas with citrus aroma, besides having a relatively high content of catechins, also contain other phenolic compounds such as naringin and hesperidin. The three assays used to evaluate the antioxidant capacity of the tea infusions gave different rank orders. Therefore an antioxidant index was calculated for better correlation of the results, and its highest value was obtained for Clear Green Mint tea infusion.

CONCLUSION

The studied teas, besides having a relatively high content of catechins, also contain naringin and hesperidin, which are not present in 'pure' green tea. It is important to run multiple assays to get a better estimate of the antioxidant capacity of a given sample.