(-)Epigallocatechin-3-gallate inhibits gelatinase activity of some bacterial isolates from ocular infection, and limits their invasion through gelatine

Potential therapeutic effects of green tea (Camellia sinensis) in eye diseases, a review

This review aims to evaluate the therapeutic potential of green tea (GT), scientifically named Camellia sinensis, in treating eye diseases. We provide an overview of the ingredients and traditional use of Camellia sinensis, followed by a detailed discussion of its therapeutic uses in various eye diseases, including ocular surface diseases (allergic diseases, dry eye, pterygium, and infections), cataract, glaucoma, uveitis, retinal diseases, and optic nerve diseases. The pharmacologic activities related to ocular diseases, such as anti-vascular endothelial growth factor, aldose reductase inhibitor activity, anti-bacterial, anti-inflammatory, and antioxidant effects are also explored in this review. The dose and route of administration of GT in various studies are discussed. Safety issues related to the use of GT, such as the side effects associated with high doses and long-term use, are also addressed. The review highlights the potential of GT as a natural therapeutic agent for a variety of ocular diseases. Its various pharmacologic activities make it a promising treatment option. However, more well-designed studies are needed to determine the optimal dose and route of administration and to assess its long-term safety and efficacy. Overall, GT appears to be a promising adjunct therapy for various ocular diseases.

Mycotoxins in milk: Occurrence and evaluation of certain detoxification attempts

Milk contaminated with mycotoxins is a significant issue affecting human health, especially in infants. The current study aimed to investigate the presence of mycotoxins in milk collected from women farmers' vendors (WFV), and to evaluate certain herbal plant fibers as green mycotoxin binders. Moreover, explore the binding efficiency ratios of mycotoxins using shaking or soaking process incorporated with herbal extracts. Furthermore, compare the taste evaluations of tested milk are enriched with herbal extracts. Results indicated that the fumonisins were not detected in the collected cow milk samples but realized a 25% occurrence ratio in buffalo's milk samples. A high occurrence ratio of aflatoxin M1 (aflaM1) was observed in buffalo and cow milk samples. The soaking process of plant fibers in contaminated milk overnight significantly degrades and adsorbs mycotoxins particles. The shacking process incorporated with plant fibers exhibited more effectiveness in mycotoxins degradation than soaking or shacking processes alone. The speed of shacking process played an important role in the mycotoxin's binding process. All the tested plant fibers effectively reduced all mycotoxin presence in contaminated milk, especially green tea, during the soaking or shacking process. Moreover, the shacking process incorporated with plant fibers promoted and supported the mycotoxins degradation process.

Preparation and Evaluation of a Xanthan Gum-Containing Linezolid Ophthalmic Solution for Topical Treatment of Experimental Bacterial Keratitis

PURPOSE

To formulate a xanthan gum-containing linezolid ophthalmic solution (LZD-XG) as a new antibiotic treatment against ocular bacterial infection.

METHODS

LZD-XG was prepared and evaluated for its in vitro/in vivo ocular tolerance, in vitro/in vivo antibacterial activity, and in vivo ocular penetration.

RESULTS

The optimized LZD-XG exhibited good in vitro/in vivo eye tolerance. A prolonged ocular surface residence time of LZD-XG was observed after topical instillation, and the ocular permeation was significantly better for LZD-XG than fora linezolid (LZD) ophthalmic solution. The in vitro antimicrobial activity was significantly better with LZD-XG than with LZD. In vivo evaluation also confirmed a strong therapeutic treatment effect of LZD-XG, as it significantly improved the clinical symptoms, ameliorated the damage of Staphylococcus aureus to ocular tissues, lowered the colony forming unit counts in the cornea, and decreased the myeloperoxidase activity in the cornea.

CONCLUSION

LZD-XG was deemed a viable ophthalmic solution against ocular bacterial infection due to its excellent in vitro and in vivo characterizations.

Antileishmanial Activity of Lignans, Neolignans, and Other Plant Phenols

Secondary metabolites (SM) from organisms have served medicinal chemists over the past two centuries as an almost inexhaustible pool of new drugs, drug-like skeletons, and chemical probes that have been used in the "hunt" for new biologically active molecules with a "beneficial effect on human mind and body." Several secondary metabolites, or their derivatives, have been found to be the answer in the quest to search for new approaches to treat or even eradicate many types of diseases that oppress humanity. A special place among SM is occupied by lignans and neolignans. These phenolic compounds are generated biosynthetically via radical coupling of two phenylpropanoid monomers, and are known for their multitarget activity and low toxicity. The disadvantage of the relatively low specificity of phenylpropanoid-based SM turns into an advantage when structural modifications of these skeletons are made. Indeed, phenylpropanoid-based SM previously have proven to offer great potential as a starting point in drug development. Compounds such as Warfarin^® (a coumarin-based anticoagulant) as well as etoposide and teniposide (podophyllotoxin-based anticancer drugs) are just a few examples. At the beginning of the third decade of the twenty-first century, the call for the treatment of more than a dozen rare or previously "neglected" diseases remains for various reasons unanswered. Leishmaniasis, a neglected disease that desperately needs new ways of treatment, is just one of these. This disease is caused by more than 20 leishmanial parasites that are pathogenic to humans and are spread by as many as 800 sandfly species across subtropical areas of the world. With continuing climate changes, the presence of Leishmania parasites and therefore leishmaniasis, the disease caused by these parasites, is spreading from previous locations to new areas. Thus, leishmaniasis is affecting each year a larger proportion of the world's population. The choice of appropriate leishmaniasis treatment depends on the severity of the disease and its form of manifestation. The success of current drug therapy is often limited, due in most cases to requiring long hospitalization periods (weeks to months) and the toxicity (side effects) of administered drugs, in addition to the increasing resistance of the parasites to treatment. It is thus important to develop new drugs and treatments that are less toxic, can overcome drug resistance, and require shorter periods of treatment. These aspects are especially important for the populations of developing countries. It was reported that several phenylpropanoid-based secondary metabolites manifest interesting antileishmanial activities and are used by various indigenous people to treat leishmaniasis. In this chapter, the authors shed some light on the various biological activities of phenylpropanoid natural products, with the main focus being on their possible applications in the context of antileishmanial treatment.

Green tea can supress rabbit ovarian functions in vitro and in vivo

The aim of present study was to evaluate the action of green tea and its constituents on rabbit ovarian functions and some non-reproductive indexes. In in vitro experiments, rabbit ovarian fragments were cultured with green tea constituents - epigallocatechin-3-gallate (EGCG), green tea polyphenols (GTPP) and resveratrol (RSV) (at 0, 1, 10 or 100 μg/mL medium). The accumulation of an apoptosis marker - caspase 3 and the release of progesterone (P4) and testosterone (T) were measured. In in vivo experiments, does were fed a standard diet or a diet enriched with green tea powder. The weight gain, mortality, ovarian length and weight, conception and kindling rate, number of liveborn, stillborn, and weaned pups, diameter of ovarian follicles and some blood haematological and biochemical parameters were analysed. Culture of ovarian fragments with EGCG increased accumulation of caspase 3, whilst both GTTP and RSV decreased it. EGCG inhibited both P4 and T output, GTPP stimulated P4 and inhibited T, whilst RSV promoted release of both P4 and T. Feeding with green tea increased ovarian length and diameter of ovarian non-ovulated peri-ovulatory haemorrhagic but not of primary and secondary growing follicles. Furthermore, green tea reduced conception and kindling rate, the number of liveborn and weaned pups, increased female mortality but not their weight gain. It reduced platelet distribution width, but it did not affect other haematological and biochemical indexes. These observations suggest that dietary green tea can reduce rabbit doe's viability, ovarian functions and fecundity, perhaps due to changes in ovarian cell apoptosis, steroid hormones release and blockade of the ovulation of large ovarian follicles. The anti-reproductive action of green tea could be due to its constituent - EGCG with pro-apoptotic and anti-steroid hormone properties.

Green tea catechins quench the fluorescence of bacteria-conjugated Alexa fluor dyes

Accumulating evidence suggests that Green tea polyphenolic catechins, especially the (-)-epigallocatechin gallate (EGCG), can be cross-linked to many proteins, and confer a wide range of anti-bacterial activities possibly by damaging microbial cytoplasmic lipids and proteins. At the doses that conferred protection against lethal polymicrobial infection (induced by cecal ligation and puncture), EGCG significantly reduced bacterial loads particularly in the liver and lung. To elucidate its bactericidal mechanisms, we determined whether EGCG affected the fluorescence intensities of bacteria-conjugated Alexa Fluor 488 or 594 dyes. When mixed with unconjugated Alexa Fluor 488 or 594 dyes, EGCG or analogs did not affect the fluorescence intensity of these dyes. In a sharp contrast, EGCG and some analogs (e.g., Catechin Gallate, CG), markedly reduced the fluorescence intensity of Gram-positive Staphylococcus aureus-conjugated Alexa 594 and Gram-negative Escherichia coli-conjugated Alexa 488. Interestingly, co-treatment with ethanol impaired the EGCG-mediated fluorescence quenching of the G(+) S. aureus, but not of the G(-) E. coli-conjugated Alexa Flour dyes. In light of the notion that Alexa Fluor dyes can be quenched by aromatic amino acids, it is plausible that EGCG exerts antimicrobial activities possibly by altering microbial protein conformations and functions. This possibility can now be explored by screening other fluorescence-quenching agents for possible antimicrobial activities.

Antimicrobial effect and membrane-active mechanism of tea polyphenols against Serratia marcescens

In this study, we investigated the antimicrobial effect of tea polyphenols (TP) against Serratia marcescens and examined the related mechanism. Morphology changes of S. marcescens were first observed by transmission electron microscopy after treatment with TP, which indicated that the primary inhibition action of TP was to damage the bacterial cell membranes. The permeability of the outer and inner membrane of S. marcescens dramatically increased after TP treatment, which caused severe disruption of cell membrane, followed by the release of small cellular molecules. Furthermore, a proteomics approach based on two-dimensional gel electrophoresis and MALDI-TOF/TOF MS analysis was used to study the difference of membrane protein expression in the control and TP treatment S. marcescens. The results showed that the expression of some metabolism enzymes and chaperones in TP-treated S. marcescens significantly increased compared to the untreated group, which might result in the metabolic disorder of this bacteria. Taken together, our results first demonstrated that TP had a significant growth inhibition effect on S. marcescens through cell membrane damage.

Epigallocatechin gallate induces upregulation of the two-component VraSR system by evoking a cell wall stress response in Staphylococcus aureus

We previously found that a short exposure of Staphylococcus aureus to subinhibitory (SI) doses of epigallocatechin gallate (EGCG) results in increased cell wall thickness, adaptation, and enhanced tolerance to cell-wall-targeted antibiotics. In this study, the response to EGCG of sigB and vraSR transcription factor mutants was characterized. We show that in contrast to the results observed for wild-type (WT) strains, an S. aureus 315 vraSR null mutant exposed to SI doses of EGCG did not exhibit increased tolerance to EGCG and oxacillin. A diminished increase in tolerance to ampicillin (from 16-fold to 4-fold) and no change in the magnitude of resistance to vancomycin were observed. Preexposure to EGCG enhanced the tolerance of wild-type and sigB null mutant cells to lysostaphin, but this enhancement was much weaker in the vraSR null mutant. Marked upregulation (about 60-fold) of vraR and upregulation of the peptidoglycan biosynthesis-associated genes murA, murF, and pbp2 (2-, 5-, and 6-fold, respectively) in response to SI doses of EGCG were determined by quantitative reverse transcription-PCR (qRT-PCR). EGCG also induced the promoter of sas016 (encoding a cell wall stress protein of unknown function which is not induced in vraSR null mutants) in a concentration-dependent manner, showing kinetics comparable to those of cell-wall-targeting antibiotics. Taken together, our results suggest that the two-component VraSR system is involved in modulating the cell response to SI doses of EGCG.

In vitro antifungal activity of epigallocatechin 3-O-gallate against clinical isolates of dermatophytes

Previously, we reported that epigallocatechin 3-O-gallate (EGCg) has growth-inhibitory effect on clinical isolates of Candida species. In this study, we investigated the antifungal activity of EGCg and antifungal agents against thirty-five of dermatophytes clinically isolated by the international guidelines (M38-A2). All isolates exhibited good susceptibility to EGCg (MIC₅₀, 2-4 μg/mL, MIC₉₀, 4-8 μg/mL, and geometric mean (GM) MICs, 3.36-4 μg/mL) than those of fluconazole (MIC₅₀, 2-16 μg/mL, MIC₉₀, 4-32 μg/mL, and GM MICs, 3.45-25.8 μg/mL) and flucytosin (MIC₅₀, MIC₉₀, and GM MICs, >64 μg/mL), although they were less susceptible to other antifungal agents, such as amphotericin B, itraconazole, and miconazole. These activities of EGCg were approximately 4-fold higher than those of fluconazole, and were 4 to 16-fold higher than flucytosin. This result indicates that EGCg can inhibit pathogenic dermatophyte species. Therefore, we suggest that EGCg may be effectively used solely as a possible agent or combined with other antifungal agents for antifungal therapy in dermatophytosis.

Staphylococcal strains adapted to epigallocathechin gallate (EGCG) show reduced susceptibility to vancomycin, oxacillin and ampicillin, increased heat tolerance, and altered cell morphology

Epigallocathechin gallate (EGCG) possesses many beneficial properties, such as anticarcinogenicity, antiatherogenicity, as well as antioxidant and antibacterial activities. However, the bacterial response to sublethal concentrations of EGCG has not been studied. Here we investigated whether short exposure of staphylococci strains to sublethal doses of EGCG can lead to adaptation and cross-resistance. Two-hour exposure of five strains to 20 microg/ml of EGCG did not affect the growth rate but significantly elevated the resistance towards antibiotics targeting the bacterial cell wall. The magnitude of cross-resistance towards such antibiotics varied with the staphylococci strain, with Staphylococcus aureus Newman exhibiting the highest magnitude of cross-resistance, showing a 2, 4 and 8-fold increase in resistance towards vancomycin, oxacillin and ampicillin respectively. All EGCG-adapted strains were also more heat tolerant than their control counterparts as derived from the Weibull model. Adaptation to EGCG led to a moderate increase in heat resistance of the adapted strains S. epidermis ATCC 12228, S. aureus Newman, and S. aureus ATCC 29213, and an extremely pronounced increase for S. aureus ATCC 6538 and S. aureus RN4220. The shape of the survival curve also varied with the staphylococci strain. Transmission electron microscopy (TEM) analysis revealed suppressed separation of daughter cells in cultures exposed to EGCG, as evidenced by the pseudomulticellular appearance and by more than 2-fold increase in cell wall thickness. These observations raise concerns over the potential of EGCG utilization in therapy in that it may contribute to the development and enhancement of microbial resistance mechanisms.

The antioxidant epigallocatechin gallate (EGCG) moderates the deleterious effects of maternal hyperthermia on follicle-enclosed oocytes in mice

Hyperthermia-induced oxidative stress is one of the mechanisms suggested to underlie loss of developmental competence in mouse embryos. In this study, we examined whether pretreatment with the antioxidant epigallocatechin gallate (EGCG) can alleviate the negative effects of hyperthermia on developmental competence of the ovarian pool of oocytes and improve embryonic development. Female mice (CB6F1) were synchronized (eCG+hCG) and injected with 0.4 ml EGCG (100 mg/kg body weight) or with saline. Both EGCG- and saline-treated mice were exposed to heat stress (HS; 40 degrees C, 65% RH) or kept under normothermal conditions (Control; 22 degrees C, 45% RH). In vivo-derived zygotes were recovered 20 h after hCG administration and cultured in vitro. Maternal hyperthermia attenuated embryonic cleavage rate in association with further disruption in embryonic early cleavage and subsequently, with embryonic development. While pretreatment with EGCG did not affect the proportion of zygotes that cleaved to the two-cell stage, it appeared to moderate the effect of hyperthermia on both cleavage timing and developmental rate, as reflected by an increased rate of early cleaved embryos and blastocyst formation. Blastocyst developmental competence was also improved, as indicated by the increased total cell number and percentage of embryos that underwent hatching, in association with reduced apoptotic status, as reflected by the percentage of TUNEL-positive cells and intensity of caspase activity for the HS-EGCG embryos vs. HS-saline ones. In summary, while hyperthermia disrupts the competence of the follicle-enclosed oocyte, in vivo administration of the antioxidant EGCG improves developmental competence and the quality of the embryos that develop from these oocytes.

Overview of antibacterial, antitoxin, antiviral, and antifungal activities of tea flavonoids and teas

Tea leaves produce organic compounds that may be involved in the defense of the plants against invading pathogens including insects, bacteria, fungi, and viruses. These metabolites include polyphenolic compounds, the six so-called catechins, and the methyl-xanthine alkaloids caffeine, theobromine, and theophylline. Postharvest inactivation of phenol oxidases in green tea leaves prevents oxidation of the catechins, whereas postharvest enzyme-catalyzed oxidation (fermentation) of catechins in tea leaves results in the formation of four theaflavins as well as polymeric thearubigins. These substances impart the black color to black teas. Black and partly fermented oolong teas contain both classes of phenolic compounds. A need exists to develop a better understanding of the roles of polyphenolic tea compounds in food and medical microbiology. This overview surveys and interprets our present knowledge of activities of tea flavonoids and teas against foodborne and other pathogenic bacteria, virulent protein toxins produced by some of the bacteria, virulent bacteriophages, pathogenic viruses and fungi. Also covered are synergistic, mechanistic, and bioavailability aspects of the antimicrobial effects. Further research is suggested for each of these categories. The herein described findings are not only of fundamental interest, but also have practical implications for nutrition, food safety, and animal and human health.

Bioassay-guided purification and identification of antimicrobial components in Chinese green tea extract

The Chinese green tea extract was found to strongly inhibit the growth of major food-borne pathogens, Escherichia coli O157:H7, Salmonella Typhimurium DT104, Listeria monocytogenes, Staphylococcus aureus, and a diarrhoea food-poisoning pathogen Bacillus cereus, by 44-100% with the highest activity found against S. aureus and lowest against E. coli O157:H7. A bioassay-guided fractionation technique was used for identifying the principal active component. A simple and efficient reversed-phase high-speed counter-current chromatography (HSCCC) method was developed for the separation and purification of four bioactive polyphenol compounds, epicatechin gallate (ECG), epigallocatechin gallate (EGCG), epicatechin (EC), and caffeine (CN). The structures of these polyphenols were confirmed with mass spectrometry. Among the four compounds, ECG and EGCG were the most active, particularly EGCG against S. aureus. EGCG had the lowest MIC90 values against S. aureus (MSSA) (58 mg/L) and its methicilin-resistant S. aureus (MRSA) (37 mg/L). Scanning electron microscopy (SEM) studies showed that these two compounds altered bacterial cell morphology, which might have resulted from disturbed cell division. This study demonstrated a direct link between the antimicrobial activity of tea and its specific polyphenolic compositions. The activity of tea polyphenols, particularly EGCG on antibiotics-resistant strains of S. aureus, suggests that these compounds are potential natural alternatives for the control of bovine mastitis and food poisoning caused by S. aureus.

Antifungal susceptibility of epigallocatechin 3-O-gallate (EGCg) on clinical isolates of pathogenic yeasts

This is the first report to investigate the antifungal susceptibility of 21 clinical isolates of seven Candida species to epigallocatechin 3-O-gallate (EGCg) and to compare with six antifungal agents, amphotericin B (AMPH), fluconazole (FLCZ), flucytosin (5FC), itraconazole (ITCZ), micafungin (MCFG), and miconazole (MCZ), using a method following the National Committee for Clinical Laboratory Standards (NCCLS) M27-A guidelines. Among the tested species, Candida glabrata exhibited the highest susceptibility to EGCg (MIC50, 0.5-1 microg/ml and MIC90, 1-2 microg/ml) compared favorably with FLCZ, although they were slightly less susceptible than to AMPH, 5FC, MCFG, ITCZ, and MCZ. Candida guilliemondii and Candida parapsilosis (MIC50, 1-4 microg/ml and MIC90, 2-16 microg/ml) were also susceptible to EGCg, although they appear to be slightly less susceptible to EGCg than C. glabrata and the other antifungal agents tested. Moreover, the susceptibility of Candida krusei strains (MIC50, 2 microg/ml and MIC90, 4-8 microg/ml) to EGCg was approximately 2- to 8-fold higher than those of 5FC and FLCZ. Our data indicate that EGCg can inhibit clinically pathogenic Candida species, although the concentrations of EGCg for antifungal susceptibility were slightly higher than those of tested antifungal agents on the whole. Based on these results, we suggest that EGCg may be effectively used as a possible agent or adjuvant for antifungal therapy in Candidiasis.

Epigallocatechin-gallate enhances the activity of tetracycline in staphylococci by inhibiting its efflux from bacterial cells

Epigallocatechin-gallate (EGCg), the major catechin present in green tea extracts, has been shown to have several antibacterial activities, limiting bacterial growth and invasion and acting in synergy with beta-lactam antibiotics. In this article, we report that EGCg at doses half and below its calculated MIC of 100 microg/ml, is able to reverse tetracycline resistance in staphylococcal isolates expressing the specific efflux pump Tet(K) and appears to improve the MICs of tetracycline for susceptible staphylococcal isolates as well. The visible effect of EGCg is an increased accumulation of tetracycline inside bacterial cells. This effect is likely due to the inhibition of pump activity, and it is evident not only for Tet(K) pumps but also for efflux pumps of a different class [Tet(B)]. In summary, our data indicate that the observed dramatic enhancement by EGCg of tetracycline activity for resistant staphylococcal isolates is caused by impairment of tetracycline efflux pump activity and increased intracellular retention of the drug, suggesting a possible use of EGCg as an adjuvant in antibacterial therapy.

Molecular epidemiology of the fsr locus and of gelatinase production among different subsets of Enterococcus faecalis isolates

We examined 215 Enterococcus faecalis isolates and found that neither the two-component regulatory locus fsr (E. faecalis regulator) nor gelatinase production was more common in disease-associated isolates than in isolates colonizing healthy individuals (ca. 60 to 65%). The majority of gelatinase-negative isolates, including 14 endocarditis isolates (of 80 isolates tested), contained the previously described 23.9-kb deletion and lacked fsrA and fsrB. While these findings indicate that neither fsr nor gelatinase is required for E. faecalis to cause infection, this study did not address whether fsr or gelatinase affects the severity of disease, as it does in animal models.

Percentage of gelatinolytic bacteria among heterotrophic bacteria as indicator of water quality

The relationship between the physiological group of gelatinolytic bacteria and the abundance of heterotrophic bacteria in freshwater ecosystems was described, based on analysis of 1082 different freshwater samples collected in Croatia. Percentages of gelatinolytic bacteria among the population of heterotrophic bacteria showed a significant negative correlation with the abundance of heterotrophic bacteria. The relation between the physiological group (gelatinolytic bacteria) and heterotrophic bacteria can be considered to be an indicator of the pollution degree of freshwaters. A high relative content of gelatinolytic bacteria (> 76%) always indicates the colony-forming units of heterotrophic bacteria < 1000/mL, which corresponds to the high water quality; gelatinolytic bacteria < 11% indicate polluted waters. Isolated strains of aerobically grown gelatinolytic bacteria were Gram-negative rod-shaped or Gram-positive endospore-forming rod-shaped cells.