Antibacterial and antifungal activities of new acylated derivatives of epigallocatechin gallate

Hoslundia opposita vahl; a potential source of bioactive compounds with antioxidant and antibiofilm activity for wound healing

BACKGROUND

Biofilms and oxidative stress retard wound healing. The resistance of biofilms to antibiotics has led to a search for alternative approaches in biofilm elimination. Antioxidants work synergistically with antibacterial agents against biofilms. Hence recent research has suggested plants as candidates in the development of new alternatives in biofilm treatments and as antioxidants due to the presence of phytocompounds which are responsible for their bioactivities. Hoslundia opposita Vahl is one of the plants used by traditional healers to treat wounds and other infections, this makes it a potential candidate for drug discovery hence, in this study, we investigate the antibiofilm and antioxidant activity of methanolic extract of hoslundia opposita Vahl from Uganda. We also identify phytochemicals responsible for its bioactivity.

METHOD

the plant was extracted by maceration using methanol, and the extract was investigated for antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay. The antibiofilm activity using microtiter plate assay (MTP) assay where the Minimum biofilm inhibitory concentration required to inhibit 50% or 90% of the biofilm (MBIC50 and MBIC90) and Minimum biofilm eradication concentration required to remove 50% or 90% of the biofilm (MBEC50 and MBEC90) were measured. It was further analysed for its phytochemical composition using quantitative screening, as well as Gas chromatography-mass spectrometry (GC-MS) and Liquid chromatography mass-spectrometry (LC-MS).

RESULTS

H. Opposita Vahl extract showed good antioxidant activity with of 249.6 mg/mL. It inhibited the growth of P. aeruginosa and S. aureus biofilms with MBIC50 of 28.37 mg/mL and 10 mg/mL, respectively. It showed the ability to eradicate P. aeruginosa and S. aureus biofilms with MBEC50 of 23.85 and 39.01 mg/mL respectively. Phytochemical analysis revealed the presence of alkaloids, tannins, flavonoids, and phenols. GC-MS analysis revealed 122 compounds in the extract of which, 23 have evidence of antioxidant or antibiofilm activity in literature. The most abundant compounds were; 1,4- Citric acid, Tetracontane-1,40-diol (43.43.3%, 1, Olean-12-en-28-oic acid, 3-hydroxy-, methyl ester, (3.beta) (15.36%) 9-Octadecenamide (12.50%), Squalene (11.85%) Palmitic Acid 4TMS (11.28%), and alpha Amyrin (11.27%). The LC-MS identified 115 and 57 compounds in multiple reaction mode (MRM) and scan modes respectively.

CONCLUSION

H. opposita Vahl showed antibiofilm and antioxidant activity due to bioactive compounds identified, hence the study justifies its use for wound healing. It can be utilised in further development of new drugs as antibiofilm and antioxidants.

Comprehensive Review of EGCG Modification: Esterification Methods and Their Impacts on Biological Activities

Epigallocatechin gallate (EGCG), the key constituent of tea polyphenols, presents challenges in terms of its lipid solubility, stability, and bioavailability because of its polyhydroxy structure. Consequently, structural modifications are imperative to enhance its efficacy. This paper comprehensively reviews the esterification techniques applied to EGCG over the past two decades and their impacts on bioactivities. Both chemical and enzymatic esterification methods involve catalysts, solvents, and hydrophobic groups as critical factors. Although the chemical method is cost-efficient, it poses challenges in purification; on the other hand, the enzymatic approach offers improved selectivity and simplified purification processes. The biological functions of EGCG are inevitably influenced by the structural changes incurred through esterification. The antioxidant capacity of EGCG derivatives can be compromised under certain conditions by reducing hydroxyl groups, while enhancing lipid solubility and stability can strengthen their antiviral, antibacterial, and anticancer properties. Additionally, esterification broadens the utility of EGCG in food applications. This review provides critical insights into developing cost-effective and environmentally sustainable selective esterification methods, as well as emphasizes the elucidation of the bioactive mechanisms of EGCG derivatives to facilitate their widespread adoption in food processing, healthcare products, and pharmaceuticals.

Tea-break with epigallocatechin gallate derivatives - Powerful polyphenols of great potential for medicine

Epigallocatechin gallate (EGCG) is a polyphenol present in green tea (Camellia sinensis), which has revealed anti-cancer effects toward a variety of cancer cells in vitro and protective potential against neurodegenerative diseases such as Alzheimer's and Parkinson's. Unfortunately, EGCG presents disappointing bioavailability after oral administration, primarily due to its chemical instability and poor absorption. Due to these limitations, EGCG is currently not used in medication, but only as a dietary supplement in the form of green tea extract. Therefore, it needs further modifications before being considered suitable for extensive medical applications. In this article, we review the scientific literature about EGCG derivatives focusing on their biological properties and potential medical applications. The most common chemical modifications of epigallocatechin gallate rely on introducing fatty acid chains or sugar molecules to its chemical structure to modify solubility. Another frequently employed procedure is based on blocking EGCG's hydroxyl groups with various substituents. Novel derivatives reveal interesting properties, of which, antioxidant, anti-inflammatory, antitumor and antimicrobial, are especially important. It is worth noting that the most promising EGCG derivatives present higher stability and activity than base EGCG.

Enzymatic molecular modification of water-soluble polyphenols: Synthesis, structure, bioactivity and application

The poor lipophilicity and instability of water-soluble polyphenols limit their bioavailability and application in food. However, increasing attention has been given to water-soluble polyphenols due to their multiple biological activities, which prompts the modification of the structure of water-soluble polyphenols to improve their lipophilicity and stability and enable more efficient application. This review presents the enzymatic biosynthesis of lipophilic derivatives of water-soluble polyphenols, which will change the molecular structure of water-soluble polyphenols based on the loss of hydroxyl or carboxyl groups. Therefore, the effects of reaction factors on the structure of polyphenol derivatives and the change in their bioactivities will be further analyzed. Previous studies have shown that lipases, solvent systems, and hydrophobic groups are major factors influencing the synthesis and lipophilicity of polyphenol derivatives. Moreover, the biological activities of polyphenol derivatives were changed to a certain extent, such as through the enhancement or weakening of antioxidant activity in different systems and the increase in anti-influenza virus activity and antibacterial activity. The improvement of lipophilicity also expands polyphenol application in food. This review may contribute to the efficient synthesis of lipophilic derivatives of water-soluble polyphenols to extend the utilization and application range of polyphenols.

Therapeutic potential of green tea catechin, (-)-epigallocatechin-3-O-gallate (EGCG) in SARS-CoV-2 infection: Major interactions with host/virus proteases

BACKGROUND

The current COVID-19 pandemic from the human pathogenic virus SARS-CoV-2 has resulted in a major health hazard globally. The morbidity and transmission modality of this disease are severe and uncontrollable. As no effective clinical drugs are available for treatment of COVID-19 infection till to date and only vaccination is used as prophylaxis and its efficacy is restricted due to emergent of new variants of SARS-CoV-2, there is an urgent need for effective drugs for its treatment.

PURPOSE

The aim of this review was to provide a detailed analysis of anti-SARS-CoV-2 efficacy of (-)-epigallocatechin-3-O-gallate (EGCG), a major catechin constituent of green tea (Camellia sinensis (L.) Kuntze) beverage to highlight the scope of EGCG in clinical medicine as both prophylaxis and treatment of present COVID-19 infection. In addition, the factors related to poor oral bioavailabilty of EGCG was also analysed for a suggestion for future research in this direction.

STUDY DESIGN

We collected the published articles related to anti-SARS-CoV-2 activity of EGCG against the original strain (Wuhan type) and its newly emerged variants of SARS-CoV-2 virus.

METHODS

A systematic search on the published literature was conducted in various databases including Google Scholar, PubMed, Science Direct and Scopus to collect the relevant literature.

RESULTS

The findings of this search demonstrate that EGCG shows potent antiviral activity against SARS-CoV-2 virus by preventing viral entry and replication in host cells in vitro models. The studies on the molecular mechanisms of EGCG in inhibition of SARS-CoV-2 infection in host cells reveal that EGCG blocks the entry of the virus particles by interaction with the receptor binding domain (RBD) of viral spike (S) protein to host cell surface receptor protease angiotensin-converting enzyme 2 (ACE2) as well as suppression of the expressions of host proteases, ACE2, TMPRSS2 and GRP78, required for viral entry, by Nrf2 activation in host cells. Moreover, EGCG inhibits the activities of SARS-CoV-2 main protease (Mpro), papain-like protease (PLpro), endoribonuclease Nsp15 in vitro models and of RNA-dependent RNA polymerase (RdRp) in molecular docking model for suppression of viral replication. In addition, EGCG significantly inhibits viral inflammatory cytokine production by stimulating Nrf2- dependent host immune response in virus-infected cells. EGCG significantly reduces the elevated levels of HMGB1, a biomarker of sepsis, lung fibrosis and thrombotic complications in viral infections. EGCG potentially inhibits the infection of original (Wuhan type) strain of SARS-CoV-2 and other newly emerged variants as well as the infections of SARS-CoV-2 virus spike-protein of WT and its mutants-mediated pseudotyped viruses . EGCG shows maximum inhibitory effect against SARS-CoV-2 infection when the host cells are pre-incubated with the drug prior to viral infection. A sorbitol/lecithin-based throat spray containing concentrated green tea extract rich in EGCG content significantly reduces SARS-CoV-2 infectivity in oral mucosa. Several factors including degradation in gastrointestinal environment, low absorption in small intestine and extensive metabolism of EGCG are responsible for its poor bioavailability in humans. Pharmacokinetic and metabolism studies of EGCG in humans reveal poor bioavailability of EGCG in human plasma and EGCG-4"-sulfate is its major metabolite. The concentration of EGCG-4"-sulfate in human plasma is almost equivalent to that of free EGCG (Cmax 177.9 vs 233.5 nmol/L). These findings suggest that inhibition of sulfation of EGCG is a crucial factor for improvement of its bioavailability. In vitro study on the mechanism of EGCG sulfonation indicates that sulfotransferases, SULT1A1 and SULT1A3 are responsible for sulfonation in human liver and small intestine, respectively. Some attempts including structural modifications, and nanoformulations of EGCG and addition of nutrients with EGCG have been made to improve the bioavailability of EGCG.

CONCLUSIONS

The findings of this study suggest that EGCG has strong antiviral activity against SARS-CoV-2 infection independent of viral strains (Wuhan type (WT), other variants) by inhibition of viral entry and replication in host cells in vitro models. EGCG may be useful in reduction of this viral load in salivary glands of COVID-19 patients, if it is applied in mouth and throat wash formulations in optimal concentrations. EGCG could be a promising candidate in the development of effective vaccine for prevention of the infections of newly emergent strains of SARS-CoV-2 virus. EGCG might be useful also as a clinical medicine for treatment of COVID-19 patients if its bioavailability in human plasma is enhanced.

The Structural Changes in the Membranes of Staphylococcus aureus Caused by Hydrolysable Tannins Witness Their Antibacterial Activity

Polyphenols, including tannins, are phytochemicals with pronounced antimicrobial properties. We studied the activity of two hydrolysable tannins, (i) gallotannin-1,2,3,4,5-penta-O-galloyl-β-D-glucose (PGG) and (ii) ellagitannin-1,2-di-O-galloyl-4,6-valoneoyl-β-D-glucose (dGVG), applied alone and in combination with antibiotics against Staphylococcus aureus strain 8324-4. We also evaluated the effect of these tannins on bacterial membrane integrity and fluidity and studied their interaction with membrane proteins and lipids. A correlation between the antimicrobial activity of the tannins and their membranotropic action depending on the tannin molecular structure has been demonstrated. We found that the antibacterial activity of PGG was stronger than dGVG, which can be associated with its larger flexibility, dipole moment, and hydrophobicity. In addition, we also noted the membrane effects of the tannins observed as an increase in the size of released bacterial membrane vesicles.

In silico prediction of flavan-3-ol as a bioactive compound of Calophyllum macrophyllum as a potential drug against angiostrongylus eosinophilic meningitis

Background and Aim:

Angiostrongylus eosinophilic meningitis is caused by larvae of the rat lungworm Angiostrongylus cantonensis. It manifests as meningitis, radiculitis, cranial nerve abnormalities, and encephalitis, which can be fatal. A flavan-3-ol compound isolated from the bark of Calophyllum macrophyllum Scheff. has several medicinal properties, including antioxidant, anti-inflammatory, antidiabetic, and antibacterial activities. This compound is stronger than other types of flavan-3-ols such as catechin. This study aimed to identify the hydroxylation pattern of this flavan-3-ol compound and evaluated its potential as an anti-meningitis drug, using an in silico approach through pharmacophore and molecular docking methods.

Materials and Methods:

Pharmacokinetic and toxicological data were analyzed and supported by the server http://www.swissadme.ch/index.php and https://tox-new.charite.de/protox_II/index.php. The hydroxylation pattern of the flavan-3-ol compound was identified using shear reagents (MeOH, NaOH, NaOAc, HCl, and AlCl₃). The CviR receptor (pdb id.3QP5) was used in the in silico approach, and seven ligands were downloaded from PubChem in “SMILES” format.

Results:

The spectroscopic analysis conducted using the shear reagents confirmed that the flavan-3-ol compound has a “p-diOH” pattern on the cinnamoyl ring. Pharmacophore analysis revealed this compound “hit” with pharmacophore features, and molecular docking analysis showed that this compound has a strong affinity with both receptors.

Conclusion:

The flavan-3-ol compound is a potential drug candidate for meningitis caused by pathogenic bacteria and the worm A. cantonensis. This result was supported by the pharmacokinetic profile, which had a very low toxicity level to the host. However, further investigation is required to confirm the data in vitro and in vivo.

Drug repurposing to overcome microbial resistance

Infections are a growing global threat, and the number of resistant species of microbial pathogens is alarming. However, the rapid development of cross-resistant or multidrug-resistant strains and the development of so-called 'superbugs' are in stark contrast to the number of newly launched anti-infectives on the market. In this review, I summarize the causes of antimicrobial resistance, briefly discuss different approaches to the discovery and development of new anti-infective drugs, and focus on drug repurposing strategy, which is discussed from all possible perspectives. A comprehensive overview of drugs of other indications tested for their in vitro antimicrobial activity to support existing anti-infective therapeutics is provided, including several critical remarks on this strategy of repurposing non-antibiotics to antibacterial drugs.

Chemico-biological aspects of (-)-epigallocatechin-3-gallate (EGCG) to improve its stability, bioavailability and membrane permeability: Current status and future prospects

Natural products have been a bedrock for drug discovery for decades. (-)-Epigallocatechin-3-gallate (EGCG) is one of the widely studied natural polyphenolic compounds derived from green tea. It is the key component believed to be responsible for the medicinal value of green tea. Significant studies implemented in in vitro, in cellulo, and in vivo models have suggested its anti-oxidant, anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial, neuroprotective activities etc. Despite having such a wide array of therapeutic potential and promising results in preclinical studies, its applicability to humans has encountered with rather limited success largely due to the poor bioavailability, poor membrane permeability, rapid metabolic clearance and lack of stability of EGCG. Therefore, novel techniques are warranted to address those limitations so that EGCG or its modified analogs can be used in the clinical setup. This review comprehensively covers different strategies such as structural modifications, nano-carriers as efficient drug delivery systems, synergistic studies with other bioactivities to improve the chemico-biological aspects (e.g., stability, bioavailability, permeability, etc.) of EGCG for its enhanced pharmacokinetics and pharmacological properties, eventually enhancing its therapeutic potentials. We think this review article will serve as a strong platform with comprehensive literature on the development of novel techniques to improve the bioavailability of EGCG so that it can be translated to the clinical applications.

Differential Hydraulic Properties and Primary Metabolism in Fine Root of Avocado Trees Rootstocks

Avocados (Persea americana Mill.) are one of the crops with the highest water footprints in Chile and the production is at risk due to severe and frequent droughts. The current production is mostly based on sexually (seed) propagated rootstocks, while clonally propagated rootstocks are on the rise. In a recent study, we found differences in aerial, root growth and water use efficiency between trees grown on these two different rootstocks under controlled continuous fertigation and environmental conditions. In this study, we further describe possible mechanisms which drive the differences. Avocado cv. "Hass" grafted on "Dusa" (D, clonally propagated) and "Mexicola" (M, sexually propagated) rootstocks and different root segments (3, 5 and 8 cm from root tip) were investigated using a combination of hydraulic measurements and polar metabolite (GC-MS) techniques. The results show significant differences in root hydraulic properties, indicating that "Mexicola" fine roots have higher water uptake capacity. The polar metabolites analysis revealed 13 compounds significantly different between rootstocks while nine were found significantly different among root segments. Principal component analysis (PCA) revealed differences between rootstocks and root segments. The data presented here highlight the importance of considering key physiological knowledge in avocado rootstocks breeding programs to be better prepared for future challenging environmental conditions.

Antibacterial, antioxidant and anti-inflammatory PLCL/gelatin nanofiber membranes to promote wound healing

Epigallocatechin-3-O-gallate (EGCG) is a green biomedical agent for promoting wound healing, which possess excellent antibacterial, antioxidant and anti-inflammatory activities. For improving the low bioavailability challenges of EGCG in vivo, we had successful created a low-cost and simple wound dressing Poly (L-Lactic-co-caprolactone) (PLCL)/Gelatin/EGCG/Core-shell nanofiber membrane (PGEC) with drug sustained release capacity through coaxial electrospinning technology. In vitro experimental indicated that the core-shell structure wound dressing had excellent biocompatibility, antibacterial and antioxidant ability, which could support cell viability and proliferation, encourage re-epithelialization during the healing process, inhibit subsequent wound infection and thus promote wound regeneration. In vivo experimental demonstrated that PGEC wound dressing could promote wound healing, the histological results further demonstrated that PGEC not only facilitated early wound closure but also influenced cellular differentiation and tissue organization. Meanwhile, PGEC had excellent hemostatic ability. Taken all together, we believed that the PGEC wound dressing, which could localize delivery of EGCG, had high potential clinical application for promoting wound healing, hemostasis or other related clinical applications in the future.

Genomic and Metabolomic Analyses of the Marine Fungus Emericellopsis cladophorae: Insights into Saltwater Adaptability Mechanisms and Its Biosynthetic Potential

The genus Emericellopsis is found in terrestrial, but mainly in marine, environments with a worldwide distribution. Although Emericellopsis has been recognized as an important source of bioactive compounds, the range of metabolites expressed by the species of this genus, as well as the genes involved in their production are still poorly known. Untargeted metabolomics, using UPLC- QToF–MS/MS, and genome sequencing (Illumina HiSeq) was performed to unlock E. cladophorae MUM 19.33 chemical diversity. The genome of E. cladophorae is 26.9 Mb and encodes 8572 genes. A large set of genes encoding carbohydrate-active enzymes (CAZymes), secreted proteins, transporters, and secondary metabolite biosynthetic gene clusters were identified. Our analysis also revealed genomic signatures that may reflect a certain fungal adaptability to the marine environment, such as genes encoding for (1) the high-osmolarity glycerol pathway; (2) osmolytes’ biosynthetic processes; (3) ion transport systems, and (4) CAZymes classes allowing the utilization of marine polysaccharides. The fungal crude extract library constructed revealed a promising source of antifungal (e.g., 9,12,13-Trihydroxyoctadec-10-enoic acid, hymeglusin), antibacterial (e.g., NovobiocinA), anticancer (e.g., daunomycinone, isoreserpin, flavopiridol), and anti-inflammatory (e.g., 2’-O-Galloylhyperin) metabolites. We also detected unknown compounds with no structural match in the databases used. The metabolites’ profiles of E. cladophorae MUM 19.33 fermentations were salt dependent. The results of this study contribute to unravel aspects of the biology and ecology of this marine fungus. The genome and metabolome data are relevant for future biotechnological exploitation of the species.

Genome and Metabolome MS-Based Mining of a Marine Strain of Aspergillus affinis

Aspergillus section Circumdati encompasses several species that express both beneficial (e.g., biochemical transformation of steroids and alkaloids, enzymes and metabolites) and harmful compounds (e.g., production of ochratoxin A (OTA)). Given their relevance, it is important to analyze the genetic and metabolic diversity of the species of this section. We sequenced the genome of Aspergillus affinis CMG 70, isolated from sea water, and compared it with the genomes of species from section Circumdati, including A. affinis's strain type. The A. affinis genome was characterized considering secondary metabolites biosynthetic gene clusters (BGCs), carbohydrate-active enzymes (CAZymes), and transporters. To uncover the biosynthetic potential of A. affinis CMG 70, an untargeted metabolomics (LC-MS/MS) approach was used. Cultivating the fungus in the presence and absence of sea salt showed that A. affinis CMG 70 metabolite profiles are salt dependent. Analyses of the methanolic crude extract revealed the presence of both unknown and well-known Aspergillus compounds, such as ochratoxin A, anti-viral (e.g., 3,5-Di-tert-butyl-4-hydroxybenzoic acid and epigallocatechin), anti-bacterial (e.g., 3-Hydroxybenzyl alcohol, l-pyroglutamic acid, lecanoric acid), antifungal (e.g., lpyroglutamic acid, 9,12,13-Trihydroxyoctadec-10-enoic acid, hydroxyferulic acid), and chemotherapeutic (e.g., daunomycinone, mitoxantrone) related metabolites. Comparative analysis of 17 genomes from 16 Aspergillus species revealed abundant CAZymes (568 per species), secondary metabolite BGCs (73 per species), and transporters (1359 per species). Some BGCs are highly conserved in this section (e.g., pyranonigrin E and UNII-YC2Q1O94PT (ACR toxin I)), while others are incomplete or completely lost among species (e.g., bikaverin and chaetoglobosins were found exclusively in series Sclerotiorum, while asperlactone seemed completely lost). The results of this study, including genome analysis and metabolome characterization, emphasize the molecular diversity of A. affinis CMG 70, as well as of other species in the section Circumdati.

The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection

Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.

Beneficial Effects of Green Tea EGCG on Skin Wound Healing: A Comprehensive Review

Epigallocatechin gallate (EGCG) is associated with various health benefits. In this review, we searched current work about the effects of EGCG and its wound dressings on skin for wound healing. Hydrogels, nanoparticles, micro/nanofiber networks and microneedles are the major types of EGCG-containing wound dressings. The beneficial effects of EGCG and its wound dressings at different stages of skin wound healing (hemostasis, inflammation, proliferation and tissue remodeling) were summarized based on the underlying mechanisms of antioxidant, anti-inflammatory, antimicrobial, angiogenesis and antifibrotic properties. This review expatiates on the rationale of using EGCG to promote skin wound healing and prevent scar formation, which provides a future clinical application direction of EGCG.

Structural characterization and antioxidant property of enzymatic-transesterification derivatives of (-)-epigallocatechin-3-O-gallate and vinyl laurate

(-)-Epigallocatechin-3-O-gallate(EGCG) was enzymatically modified to enhance the lipophilicity and the antioxidant property. The determination of optimal reaction conditions are as follows: Lipase DF "Amano" 15 and acetone were used as catalyst and solvent, respectively. Equal molar of EGCG and vinyl laurate (1:1); lipase addition of 6.0% (w/w of total substrates); reaction temperature of 50°C and reaction time of 96 h, which obtained the conversion rate of EGCG at 80.1%. The structure of EGCG lauroyl derivatives were 5″-O-lauroyl-EGCG, 3″,5″-2-O-lauroyl-EGCG, and 5',3″,5″-3-O-lauroyl-EGCG, identified by high-performance liquid chromatography-mass spectrometry (HPLC-MS) and nuclear magnetic resonance (NMR). Compared with the logP of precursor EGCG (0.69 ± 0.03), the logP of EGCG lauroyl derivatives was 1.37 ± 0.19, 2.27 ± 0.33, and 3.28 ± 0.37, increasing by 0.98, 2.28, and 3.75 times, respectively (p < 0.05), suggesting the grafted fatty acid chains make EGCG derivatives more lipophilic, and the lipid solubility gradually increased as the number of substituents increased. Furthermore, EGCG lauroyl derivatives had excellent lipid oxidation than that of EGCG. The POVs (peroxide values) of soybean oil with mono-, di-, tri-lauroyl EGCG were significantly reduced by 42%, 47%, and 57% than that of EGCG at 21 days, respectively, indicating the antioxidative inhibition of these derivatives decreased with the increase in substituents. This indicates that these derivatives have broad prospects of the antioxidant application while improving their solubility properties in lipophilic environments/high-fat food. Practical Application: The lipophilic esterification reaction of EGCG catalyzed by new catalytic lipase DF "Amano" 15 was carried out in a non-aqueous solvent.Various reaction factors on a higher conversion rate of EGCG lauroyl derivatives were evaluated. The lipophilicity and antioxidant properties of EGCG lauroyl derivatives were much excellent than that of parent EGCG.

Recovery of Polyphenolic Fraction from Arabica Coffee Pulp and Its Antifungal Applications

Coffee pulp is one of the most underutilised by-products from coffee processing. For coffee growers, disposing of this agro-industrial biomass has become one of the most difficult challenges. This study utilised this potential biomass as raw material for polyphenolic antifungal agents. First, the proportion of biomass was obtained from the Arabica green bean processing. The yield of by-products was recorded, and the high-potency biomass was serially extracted with organic solvents for the polyphenol fraction. Quantification of the polyphenols was performed by High Performance Liquid Chromatography (HPLC), then further confirmed by mass spectrometry modes of the liquid chromatography–quadrupole time-of-flight (QTOF). Then, the fraction was used to test antifungal activities against Alternaria brassicicola, Pestalotiopsis sp. and Paramyrothecium breviseta. The results illustrated that caffeic acid and epigallocatechin gallate represented in the polyphenol fraction actively inhibited these fungi with an inhibitory concentration (IC50) of 0.09, 0.31 and 0.14, respectively. This study is also the first report on the alternative use of natural biocontrol agent of P. breviseta, the pathogen causing leaf spot in the Arabica coffee.

Flavonoids as Promising Antiviral Agents against SARS-CoV-2 Infection: A Mechanistic Review

A newly diagnosed coronavirus in 2019 (COVID-19) has affected all human activities since its discovery. Flavonoids commonly found in the human diet have attracted a lot of attention due to their remarkable biological activities. This paper provides a comprehensive review of the benefits of flavonoids in COVID-19 disease. Previously-reported effects of flavonoids on five RNA viruses with similar clinical manifestations and/or pharmacological treatments, including influenza, human immunodeficiency virus (HIV), severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and Ebola, were considered. Flavonoids act via direct antiviral properties, where they inhibit different stages of the virus infective cycle and indirect effects when they modulate host responses to viral infection and subsequent complications. Flavonoids have shown antiviral activity via inhibition of viral protease, RNA polymerase, and mRNA, virus replication, and infectivity. The compounds were also effective for the regulation of interferons, pro-inflammatory cytokines, and sub-cellular inflammatory pathways such as nuclear factor-κB and Jun N-terminal kinases. Baicalin, quercetin and its derivatives, hesperidin, and catechins are the most studied flavonoids in this regard. In conclusion, dietary flavonoids are promising treatment options against COVID-19 infection; however, future investigations are recommended to assess the antiviral properties of these compounds on this disease.

Antibacterial activity and mechanism of plant flavonoids to gram-positive bacteria predicted from their lipophilicities

Antimicrobial resistance seriously threatened human health, and new antimicrobial agents are desperately needed. As one of the largest classes of plant secondary metabolite, flavonoids can be widely found in various parts of the plant, and their antibacterial activities have been increasingly paid attention to. Based on the physicochemical parameters and antibacterial activities of sixty-six flavonoids reported, two regression equations between their ACD/LogP or LogD_7.40 and their minimum inhibitory concentrations (MICs) to gram-positive bacteria were established with the correlation coefficients above 0.93, and then were verified by another sixty-eight flavonoids reported. From these two equations, the MICs of most flavonoids against gram-positive bacteria could be roughly calculated from their ACD/LogP or LogD_7.40, and the minimum MIC was predicted as approximately 10.2 or 4.8 μM, more likely falls into the range from 2.6 to 10.2 μM, or from 1.2 to 4.8 μM. Simultaneously, both tendentiously concave regression curves indicated that the lipophilicity is a key factor for flavonoids against gram-positive bacteria. Combined with the literature analyses, the results also suggested that the cell membrane is the main site of flavonoids acting on gram-positive bacteria, and which likely involves the damage of phospholipid bilayers, the inhibition of the respiratory chain or the ATP synthesis, or some others.

Controlled bacteriostasis of tea polyphenol loaded ultrahigh molecular weight polyethylene with high crosslink density and oxidation resistance for total joint replacement

To avoid catastrophic bacterial infection in prosthesis failure, ultrahigh molecular weight polyethylene (UHMWPE), a common bearing material of artificial joints, has been formulated with antibiotics to eliminate bacteria locally at the implant site. However, the pressing issues regarding cytotoxic effects and evolution of drug resistant bacteria necessitates the development of bio-friendly bacteriostat with long bacteriostatic efficacy. Herein, tea polyphenol extracted from nature source was introduced in UHMWPE as a biogenic antimicrobial. Controlled antimicrobial activity was achieved by chemical crosslinking to regulate the release of the tea polyphenol. In addition, the crosslinking efficiency of UHMWPE blends with high loaded tea polyphenol was significantly improved in comparison to radiation crosslinking. The immobilized tea polyphenols also enhanced the oxidation stability of the UHMWPE, which is essential to prolong the service life in vivo and the storage time in vitro. The blends presented good biocompatibility, despite cell repellent on the highly crosslinked surface. Chemically crosslinked tea polyphenol/UHMWPE exhibited feasible properties for total joint implants, which is promising for clinical application.

Synthesis, Stability, and Antidiabetic Activity Evaluation of (-)-Epigallocatechin Gallate (EGCG) Palmitate Derived from Natural Tea Polyphenols

This work describes a novel approach for the synthesis of (−)-epigallocatechin gallate (EGCG) palmitate by a chemical-synthesis method, where the elevated stability of the EGCG derivative is achieved. Various parameters affecting the acylation process, such as the base, solvent, as well as the molar ratio of palmitoyl chloride, have been studied to optimize the acylation procedure. The optimized reaction condition was set as follows: EGCG/palmitoyl chloride/sodium acetate was under a molar ratio of 1:2:2, with acetone as the solvent, and the reaction temperature was 40 °C. Under the optimized condition, the yield reached 90.6%. The EGCG palmitate (PEGCG) was isolated and identified as 4′-O-palmitoyl EGCG. Moreover, the stability of PEGCG under different conditions was proved significantly superior to EGCG. Finally, PEGCG showed better inhibition towards α-amylase and α-glucosidase, which was 4.5 and 52 times of EGCG, respectively. Molecular docking simulations confirmed the in vitro assay results. This study set a novel and practical synthetic approach for the derivatization of EGCG, and suggest that PEGCG may act as an antidiabetic agent.

Epigallocatechin-3-Gallate (EGCG) Inhibits SARS-CoV-2 Infection in Primate Epithelial Cells: (A Short Communication)

SARS-CoV-2, the novel coronavirus responsible for the COVID-19 pandemic, caused >26 million cases in the United States and >437,000 deaths as of Jan 30, 2020. Worldwide by that date, there had been 102 million cases of infections, and deaths had climbed to 2.21 million. Mutated variants of SARS-CoV-2 that have emerged from the United Kingdom, Brazil, and South Africa are associated with higher transmission rates and associated deaths. Therefore, novel therapeutic and prophylactic methods against SARS-CoV-2 are in urgent need. While some antiviral drugs, such as Remdesivir, provide relief to certain patient populations, other existing antiviral drugs or combinations of FDA approved pharmaceuticals have yet to show clinical efficacy against COVID-19. Compounds that possess strong and broad antiviral properties with different mechanisms of action against respiratory viruses may provide novel approaches to combat SARS-CoV-2 and its variants, especially if the compounds are classified as generally recognized as safe (GRAS). A large body of evidence indicates a promising potential for the use of epigallocatechin-3-gallate (EGCG) and its derivatives as effective agents against infections from a wide range of pathogenic viruses. However, EGCG or its derivatives have not been tested directly against SARS-CoV-2. The current study was designed to evaluate the potential antiviral activity of EGCG against SARS-CoV-2 infection in primate epithelial cells. Methods applied in the study include cytopathic effect (CPE) assay and virus yield reduction (VYR) assays using Vero 76 (green monkey epithelial cells) and Caco-2 (human epithelial cells) cell lines, respectively. The results demonstrated that EGCG at 0.27 μg/ml (0.59 μM) inhibited SARS-CoV-2 infection in Vero 76 cells by 50% (i.e., EC50=0.27 μg/ml). EGCG also inhibited SARS-CoV-2 infection in Caco-2 cells with EC90=28 μg/ml (61 μM). These results, to the best of our knowledge, are the first observations on the antiviral activities of EGCG against SARS-CoV-2, and suggest that EGCG and its derivatives could be used to combat COVID-19 and other respiratory viral infection-induced illness, pending in vivo and clinical studies.

Polyphenol-Assisted Chemical Crosslinking: A New Strategy to Achieve Highly Crosslinked, Antioxidative, and Antibacterial Ultrahigh-Molecular-Weight Polyethylene for Total Joint Replacement

Highly crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE) bearings are wear-resistant to reduce aseptic loosening but are susceptible to oxidize in vivo/in vitro, as reported in clinical studies. Despite widespread acceptance of antioxidants in preventing oxidation, the crosslinking efficiency of UHMWPE is severely impacted by antioxidants, the use of which was trapped in a trace amount. Herein, we proposed a new strategy of polyphenol-assisted chemical crosslinking to facilitate the formation of a crosslinking network in high-loaded tea polyphenol/UHMWPE blends. Epigallocatechin gallate (EGCG), a representative of tea polyphenol, was mixed with UHMWPE and peroxide. Multiple reactive phenolic hydroxyl groups of tea polyphenol coupled with the nearby free radicals to form extra crosslinking sites. The crosslinking efficiency was remarkably enhanced with increasing tea polyphenol content, even at a concentration of 8 wt %. Given by the hydrogen donation principle, the high-loaded tea polyphenol also enhanced the oxidation stability of the crosslinked UHMWPE. The antioxidative performance was preserved even after tea polyphenol elution. Moreover, superior antibacterial performance was achieved by the in situ tea polyphenol release from the interconnected pathways in the present design. The strategy of polyphenol-assisted chemical crosslinking is applicable for producing highly crosslinked, antioxidative, and antibacterial UHMWPE, which has promising prospects in clinical applications.

Secondary metabolites of endophytic fungi from Newbouldia laevis and Cassia tora leaves: prospecting for new antimicrobial agents

AIM

This study tries to prospect for new antimicrobial agents using some Nigerian plants Background: Antimicrobial compounds from fungi endophytes have shown great promise in mitigating the threats of resistant pathogens.

OBJECTIVE

The study evaluated the in vitro antimicrobial property of secondary metabolites of endophytic fungi isolated from Newbouldia laevis and Cassia tora leaves.

METHODS

Ten endophytic fungi were isolated from the two plants' leaves and later fermented on local rice for 21 days. Thereafter, their secondary metabolites were extracted using ethyl acetate. The antibacterial activity of the extracts on the test organisms were determined using agar diffusion and agar dilution methods, while the bioactive constituents were identified using High performance liquid chromatography coupled to diode array detector.

RESULTS

Nine of the crude extracts (NL1, NL3, NL6, NL10, NL12, CT2, CT7, CT9 and CT10) of the fungi isolates inhibited at least one of the microorganisms studied with maximum and minimum Inhibition-Zone-Diameter of 14 mm and 2 mm respectively while CT1 did not inhibit any of the tested microorganisms at tested concentrations. The extracts exhibited good antifungal activity, inhibiting the growth of both C. albicans and Trichophyton tested with an InhibitionZone-Diameter ranging between 4-8 mm and 7-14 mm respectively. The endophytic fungi extracts- CT2 and NL1- exhibited the best antimicrobial activity, inhibiting most of the tested microorganisms. HPLC-DAD analysis of the endophytic fungal extracts identified some classes of compounds such as catechin derivatives, benzoic acid derivatives and apigenin, which were previously reported to have antimicrobial potentials.

CONCLUSION

Newbouldia laevis and Cassia tora leaves house endophytic fungi capable of yielding secondary metabolites with potential as anti-infective agents.

Antioxidant Molecules from Plant Waste: Extraction Techniques and Biological Properties

The fruit, vegetable, legume, and cereal industries generate many wastes, representing an environmental pollution problem. However, these wastes are a rich source of antioxidant molecules such as terpenes, phenolic compounds, phytosterols, and bioactive peptides with potential applications mainly in the food and pharmaceutical industries, and they exhibit multiple biological properties including antidiabetic, anti-obesity, antihypertensive, anticancer, and antibacterial properties. The aforementioned has increased studies on the recovery of antioxidant compounds using green technologies to value plant waste, since they represent more efficient and sustainable processes. In this review, the main antioxidant molecules from plants are briefly described and the advantages and disadvantages of the use of conventional and green extraction technologies used for the recovery and optimization of the yield of antioxidant naturals are detailed; finally, recent studies on biological properties of antioxidant molecules extracted from plant waste are presented here.

Opportunities and challenges in managing antibiotic resistance in bacteria using plant secondary metabolites

Development of antibiotic resistance (ABR) in bacteria and its multidimensional spread is an emerging global threat that needs immediate attention. Extensive antibiotics (AB) usage results in development of ABR in bacteria by target modification, production of AB degrading enzymes, porin modifications, efflux pumps overexpression, etc. To counter this, apart from strict regulation of AB use and behavioural changes, research and development (R&D) of newer antimicrobials are in place. One such emerging approach to combat ABR is the use of structurally and functionally diverse plant secondary metabolites (PSMs) in combination with the conventional AB. Either the PSMs are themselves antimicrobial or they potentiate the activity of the AB through a range of mechanisms. However, their use is lagging due to poor knowledge of mode of action, structure-activity relationships, pharmacokinetics, etc. This review paper discussed the opportunities and challenges in managing ABR using PSMs. Mechanisms of ABR development in bacteria and current strategies to counter them were studied and the areas where PSMs can play an important role were highlighted. The use of PSMs, both as an anti-resistance and anti-virulence agent in combination therapy to counter multi-drug resistance along with their mechanisms of action, has been discussed in detail. The difficulties in the commercialisation of PSMs and strategies to overcome them along with future priority areas of research have also been given. Following the given R&D path will definitely help in better understanding and utilising the full potential of PSMs in solving the problem of antimicrobial resistance (AMR).

Targeted Pulmonary Delivery of the Green Tea Polyphenol Epigallocatechin Gallate Controls the Growth of Mycobacterium tuberculosis by Enhancing the Autophagy and Suppressing Bacterial Burden

Growing rates of tuberculosis (TB) superbugs are alarming, which has hampered the progress made to-date to control this infectious disease, and new drug candidates are few. Epigallocatechin gallate (EGCG), a major polyphenolic compound from green tea extract, shows powerful efficacy against TB bacteria in in vitro studies. However, the therapeutic efficacy of the molecule is limited due to poor pharmacokinetics and low bioavailability following oral administration. Aiming to improve the treatment outcomes of EGCG therapy, we investigated whether encapsulation and pulmonary delivery of the molecule would allow the direct targeting of the site of infection without compromising the activity. Microencapsulation of EGCG was realized by scalable spray-freeze-drying (SFD) technology, forming free-flowing micrometer-sized microspheres (epigallocatechin-3-gallate-loaded trehalose microspheres, EGCG-t-MS) of trehalose sugar. These porous microspheres exhibited appropriate aerodynamic parameters and high encapsulation efficiencies. In vitro studies demonstrated that EGCG-t-MS exhibited dose- and time-dependent killing of TB bacteria inside mouse macrophages by cellular mechanisms of lysosome acidification and autophagy induction. In a preclinical study on TB-infected Balb/c mice model (4 weeks of infection), we demonstrate that the microencapsulated EGCG, administered 5 days/week for 6 weeks by pulmonary delivery, showed exceptional efficacy compared to oral treatment of free drug. This treatment approach exhibited therapeutic outcomes by resolution of inflammation in the infected lungs and significant reduction (P < 0.05) in bacterial burden (up to ∼2.54 Log₁₀ CFU) compared to untreated control and orally treated mice groups. No pathological granulomas, lesions, and inflammation were observed in the histopathological investigation, compared to untreated controls. The encouraging results of the study may pave the avenues for future use of EGCG in TB therapeutics by targeted pulmonary delivery and lead to its translational success.

The Inhibitory Effect of Plant Extracts on Growth of the Foodborne Pathogen, Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen responsible for about 1600 illnesses each year in the United States (US) and about 2500 confirmed invasive human cases in European Union (EU) countries. Several technologies and antimicrobials are applied to control the presence of L. monocytogenes in food. Among these, the use of natural antimicrobials is preferred by consumers. This is due to their ability to inhibit the growth of foodborne pathogens but not prompt negative safety concerns. Among natural antimicrobials, plant extracts are used to inactivate L. monocytogenes. However, there is a large amount of these types of extracts, and their active compounds remain unexplored. The aim of this study was to evaluate the antibacterial activity against L. monocytogenes of about 800 plant extracts derived from plants native to different countries worldwide. The minimal inhibitory concentrations (MICs) were determined, and scanning electron microscopy (SEM) was used to verify how the plant extracts affected L. monocytogenes at the microscopic level. Results showed that 12 of the plant extracts had inhibitory activity against L. monocytogenes. Future applications of this study could include the use of these plant extracts as new preservatives to reduce the risk of growth of pathogens and contamination in the food industry from L. monocytogenes.

Epigallocatechin-3-gallate (EGCG) exert therapeutic effect on acute inflammatory otitis media in rats

INTRODUCTION

That EGCG has strong antioxidant and anti-inflammatory activities as well as antibacterial activity against many streptococcus species suggests that it may be beneficial in the treatment of AOM.

OBJECTIVE

Aim of the study is to reveal the molecular and biochemical effects of EGCG on LPS induced otitis media in rats.

METHODS

Forty-two male albino Wistar rats were randomly divided into 7 groups. Inflammation was induced by administrating 50 μL of 1 mg/ml lipopolysaccharide (LPS). EGCG used 50 and 100 mg/kg/day and combined penicillin G (PENG) 48 h after LPS injection.

RESULTS

The combined EGCG 50 and PENG group and the group with EGCG 50 alone showed the best anti-inflammatory effect on LPS-induced AOM. TNF-α and IL-1β gene expression significantly down regulated EGCG 50 and combined with PENG compared to the otitis media group. The combination of PenG and EGCG 50 led to the best histopathological improvement. Both the inflammation and the membrane thickness of this group were at almost the same level as the healthy group and tympanum was seen normal.

CONCLUSION

The results of this study make it clear that EGCG plays an important role in antioxidant and anti-inflammatory activity during AOM.

Structural and energetic basis for the molecular recognition of dual synthetic vs. natural inhibitors of EGFR/HER2

Activation of EGFR starts by ligand binding at the extracellular domain which results in homo and heterodimerization, leading to phosphorylation, activation of downstream signaling pathways which upregulate expression of genes, proliferation and angiogenesis. Abnormalities in the expression of EGFR play a critical role in the development of different types of cancer. HER2 is the preferred heterodimerization partner for EGFR; this biological characteristic together with the high percentage of structural homology has been exploited in the design of dual synthetic inhibitors against EGFR/HER2. Herein we combined structural data and molecular dynamics (MD) simulations coupled to an MMGBSA approach to provide insight into the binding mechanism between two dual synthetics (lapatinib and TAK-285) and one dual natural inhibitor (EGCG) which target EGFR/HER2. In addition, we proposed some EGCG derivatives which were filtered through in silico screening. Structural analysis demonstrated that the coupling of synthetic, natural or newly designed compounds impacts the conformational space of EGFR and HER2 differently. Energetic analysis points out that lapatinib and TAK-285 have better affinity for inactive EGFR than the active EGFR state or HER2, whereas some EGCG derivatives seem to form binding affinities similar to those observed for lapatinib or TAK-285.

Characterization of Lipophilized Monomeric and Oligomeric Grape Seed Flavan-3-ol Derivatives

Grape seed proanthocyanidins, composed of flavan-3-ols of different degrees of polymerization, are natural food antioxidants. Flavan-3-ols in grape seed are usually polyhydroxy derivatives which exhibit hydrophilic character. Monomeric and oligomeric flavan-3-ols were modified structurally to improve their lipophilicity, expand their application in lipophilic media, and enhance their cellular absorption in the body. The esterification of the water-soluble flavan-3-ols was prepared by Lipozyme TL IM with lauric acid, and their enhanced lipophilicity was confirmed by a 1-octanol/water partition coefficient. The chemical structures of monomeric and oligomeric flavan-3-ol derivatives, identified by HPLC-MS-MS and ¹H and ¹³C NMR, were 3'-O-lauroyl catechin, 3'-O-lauroyl epicatechin, 3',5'-2-O-lauroyl epigallocatechin, 3',3″,5″-3-O-lauroyl epicatechin gallate, 3',3″-2-O-lauroyl procyanidin A2, 3',3″-2-O-lauroyl procyanidin B1, and 3',3″,3‴-3-O-lauroyl procyanidin C1. Flavan-3-ol derivatives exhibited the highest 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activities compared to that of parent flavan-3-ols, butylated hydroxytoluene and tert-butyl hydroquinone. The results suggest that flavan-3-ol derivatives may be used as potential lipophilic antioxidants in the food industry.

A Review of the Antiviral Role of Green Tea Catechins

Over the centuries, infectious diseases caused by viruses have seriously threatened human health globally. Viruses are responsible not only for acute infections but also many chronic infectious diseases. To prevent diseases caused by viruses, the discovery of effective antiviral drugs, in addition to vaccine development, is important. Green tea catechins (GTCs) are polyphenolic compounds from the leaves of Camelliasinensis. In recent decades, GTCs have been reported to provide various health benefits against numerous diseases. Studies have shown that GTCs, especially epigallocatechin-3-gallate (EGCG), have antiviral effects against diverse viruses. The aim of this review is to summarize the developments regarding the antiviral activities of GTCs, to discuss the mechanisms underlying these effects and to offer suggestions for future research directions and perspectives on the antiviral effects of EGCG.

Lipophilized Grape Seed Proanthocyanidin Derivatives as Novel Antioxidants

Grape seed proanthocyanidin (GSP) is a natural food antioxidant. Natural proanthocyanidins (PC) in grape seed are usually polyhydroxy derivatives which exhibit hydrophilic character. GSP was modified structurally to improve its lipophilicity, expand its application in lipophilic media, and enhance its cellular absorption in vivo. Esterification of the water-soluble GSP was prepared by immobilized lipase Lipozyme TL IM with lauric acid, and their enhanced lipophilicity was confirmed by the 1-octanol/water partition coefficient. The presence of mono-, di-, and trilauroylated derivatives in GSP derivatives was confirmed by HPLC-MS-MS, and four lauroylated derivatives were identified as 3',5'-2-O-lauroyl epigallocatechin, 3'-O-lauroyl catechin, 3'-O-lauroyl epicatechin, and 3',3″,5″-3-O-lauroyl epicatechin gallate by NMR. GSP derivatives exhibited the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC₅₀ of 41 μg/mL) compared to that of GSP, hydroxytoluene (BHT), and tert-butyl hydroquinone (TBHQ). The results suggest that GSP derivatives may be used as potential lipophilic antioxidants in the food industry.

Nematode Peptides with Host-Directed Anti-inflammatory Activity Rescue Caenorhabditis elegans from a Burkholderia pseudomallei Infection

Burkholderia pseudomallei, the causative agent of melioidosis, is among a growing number of bacterial pathogens that are increasingly antibiotic resistant. Antimicrobial peptides (AMPs) have been investigated as an alternative approach to treat microbial infections, as generally, there is a lower likelihood that a pathogen will develop resistance to AMPs. In this study, 36 candidate Caenorhabditis elegans genes that encode secreted peptides of <150 amino acids and previously shown to be overexpressed during infection by B. pseudomallei were identified from the expression profile of infected nematodes. RNA interference (RNAi)-based knockdown of 12/34 peptide-encoding genes resulted in enhanced nematode susceptibility to B. pseudomallei without affecting worm fitness. A microdilution test demonstrated that two peptides, NLP-31 and Y43C5A.3, exhibited anti-B. pseudomallei activity in a dose dependent manner on different pathogens. Time kill analysis proposed that these peptides were bacteriostatic against B. pseudomallei at concentrations up to 8× MIC90. The SYTOX green assay demonstrated that NLP-31 and Y43C5A.3 did not disrupt the B. pseudomallei membrane. Instead, gel retardation assays revealed that both peptides were able to bind to DNA and interfere with bacterial viability. In parallel, microscopic examination showed induction of cellular filamentation, a hallmark of DNA synthesis inhibition, of NLP-31 and Y43C5A.3 treated cells. In addition, the peptides also regulated the expression of inflammatory cytokines in B. pseudomallei infected macrophage cells. Collectively, these findings demonstrate the potential of NLP-31 and Y43C5A.3 as anti-B. pseudomallei peptides based on their function as immune modulators.

Bacterial lipid membranes as promising targets to fight antimicrobial resistance, molecular foundations and illustration through the renewal of aminoglycoside antibiotics and emergence of amphiphilic aminoglycosides

Membrane anionic lipids as attractive targets in the design of amphiphilic antibacterial drugs active against resistant bacteria: molecular foundations and examples.

Bioavailability of dietary polyphenols and gut microbiota metabolism: antimicrobial properties

Polyphenolic compounds are plant nutraceuticals showing a huge structural diversity, including chlorogenic acids, hydrolyzable tannins, and flavonoids (flavonols, flavanones, flavan-3-ols, anthocyanidins, isoflavones, and flavones). Most of them occur as glycosylated derivatives in plants and foods. In order to become bioactive at human body, these polyphenols must undergo diverse intestinal transformations, due to the action of digestive enzymes, but also by the action of microbiota metabolism. After elimination of sugar tailoring (generating the corresponding aglycons) and diverse hydroxyl moieties, as well as further backbone reorganizations, the final absorbed compounds enter the portal vein circulation towards liver (where other enzymatic transformations take place) and from there to other organs, including behind the digestive tract or via blood towards urine excretion. During this transit along diverse tissues and organs, they are able to carry out strong antiviral, antibacterial, and antiparasitic activities. This paper revises and discusses these antimicrobial activities of dietary polyphenols and their relevance for human health, shedding light on the importance of polyphenols structure recognition by specific enzymes produced by intestinal microbial taxa.

Effect of green tea extract and mouthwash without alcohol on Candida albicans biofilm on acrylic resin

OBJECTIVE

To evaluate the effect of aqueous extract of green tea and the oral antiseptic without alcohol, on Candida albicans biofilm formation to heat-curing acrylic resin plates.

BACKGROUND

Candida is associated with oral candidiasis in poorly cleaned dentures.

MATERIAL AND METHODS

Standardised specimens of heat-cured (Conv; n = 30) or microwave-cured acrylic resin (Mw; n = 30) were obtained and divided into six groups (n = 10): G1 = Conv resin and green tea aqueous extract, G2 = Conv resin and mouthwash, G3 = control of Conv resin, G4 = Mw resin and green tea aqueous extract, G5 = Mw resin and mouthwash and G6 = control of Mw-cured resin. The specimens were contaminated with 10 ml of Sabouraud dextrose broth inoculated with 0.1 ml of standard suspension containing 1 × 10(6) cells/ml of C. albicans and incubated for 24 h at 37°C. After this period, they were immersed in the aqueous extract or in mouthwash for 15 min. The control groups were treated with sterile distilled water. Aliquots of 0.1 ml were plated on Sabouraud dextrose agar and incubated at 37°C for 24 h. The numbers of colony-forming units per test specimen (CFU/TS) were calculated, and the results statistically analysed by two-way anova and Tukey's tests (5%).

RESULTS

Statistically significant difference was observed for the aqueous extract groups (G1; 33.65%) and mouthwash (G2; 17.06%), when compared to control (G3; 100%), for Conv resin. For the Mw resin, there was significant difference between mouthwash (G5; 43.16%) and control (G6; 100%).

CONCLUSION

The aqueous extract of green tea and mouthwash led to a reduction in the number of viable fungal cells in biofilm formed on acrylic resin.

Anti-infective properties of epigallocatechin-3-gallate (EGCG), a component of green tea

The consumption of green tea (Camellia sinensis) has been shown to have many physiological and pharmacological health benefits. In the past two decades several studies have reported that epigallocatechin-3-gallate (EGCG), the main constituent of green tea, has anti-infective properties. Antiviral activities of EGCG with different modes of action have been demonstrated on diverse families of viruses, such as Retroviridae, Orthomyxoviridae and Flaviviridae and include important human pathogens like human immunodeficiency virus, influenza A virus and the hepatitis C virus. Furthermore, the molecule interferes with the replication cycle of DNA viruses like hepatitis B virus, herpes simplex virus and adenovirus. Most of these studies demonstrated antiviral properties within physiological concentrations of EGCG in vitro. In contrast, the minimum inhibitory concentrations against bacteria were 10-100-fold higher. Nevertheless, the antibacterial effects of EGCG alone and in combination with different antibiotics have been intensively analysed against a number of bacteria including multidrug-resistant strains such as methicillin-resistant Staphylococcus aureus or Stenotrophomonas maltophilia. Furthermore, the catechin EGCG has antifungal activity against human-pathogenic yeasts like Candida albicans. Although the mechanistic effects of EGCG are not fully understood, there are results indicating that EGCG binds to lipid membranes and affects the folic acid metabolism of bacteria and fungi by inhibiting the cytoplasmic enzyme dihydrofolate reductase. This review summarizes the current knowledge and future perspectives on the antibacterial, antifungal and antiviral effects of the green tea constituent EGCG.

Effects of the medicinal plants Curcuma zedoaria and Camellia sinensis on halitosis control

Volatile sulphur compounds (VSC) are the gases mainly responsible for halitosis (bad breath). The aim of this research was to evaluate the effects of medicinal plants on halitosis control. Two commonly used plants were tested: Curcuma zedoaria and Camellia sinensis (green tea). These plants were prepared as an aqueous solution and used as mouthwashes, compared with a standard mouthwash of 0.12% chlorhexidine gluconate and a placebo (water). The experiment was conducted with 30 volunteers from the School of Dentistry of São Jose dos Campos, Univ. Estadual Paulista - UNESP, SP, Brazil. Each volunteer tested the four mouthwashes. The Cysteine Challenge Method, modified for this study, was used for initial breath standardization. Four breath assessments were conducted after volunteers rinsed orally with acetylcysteine: one before the test mouthwash was used; the second, one minute after its use; a third 90 minutes later; and the last 180 minutes later. The results showed that chlorhexidine gluconate lowered VSC production immediately, and that this effect lasted up to 3 hours, while the tested plants had immediate inhibitory effects but no residual inhibitory effects on VSC. We concluded that Curcuma zedoaria and Camellia sinensis, prepared as infusions and used as mouthwashes, did not have a residual neutralizing effect on VSC.