Novel Antifungal Mechanism of Resveratrol: Apoptosis Inducer in Candida albicans

Pistacia vera L. as natural source against antimicrobial and antiviral resistance

Increased global research is focused on the development of novel therapeutics to combat antimicrobial and antiviral resistance. Pistachio nuts represent a good source of protein, fiber, monounsaturated fatty acids, minerals, vitamins, and phytochemicals (carotenoids, phenolic acids, flavonoids and anthocyanins). The phytochemicals found in pistachios are structurally diverse compounds with antimicrobial and antiviral potential, demonstrated as individual compounds, extracts and complexed into nanoparticles. Synergistic effects have also been reported in combination with existing drugs. Here we report an overview of the antimicrobial and antiviral potential of pistachio nuts: studies show that Gram-positive bacterial strains, such as Staphylococcus aureus, are the most susceptible amongst bacteria, whereas antiviral effect has been reported against herpes simplex virus 1 (HSV-1). Amongst the known pistachio compounds, zeaxanthin has been shown to affect both HSV-1 attachment penetration of human cells and viral DNA synthesis. These data suggest that pistachio extracts and derivatives could be used for the topical treatment of S. aureus skin infections and ocular herpes infections.

The flexural strength of orthodontic acrylic resin containing resveratrol nanoparticles as antimicrobial agent: An in vitro study

OBJECTIVE

This study aimed to evaluate how the addition of resveratrol nanoparticles (RNPs), which act as an antimicrobial agent, affects the strength of acrylic resin used in orthodontics.

METHODS

According to ISO 20795-1-2013, 76 cold cure acrylic resin samples (65×10×3.3mm) were prepared. The samples were divided into four groups (19 samples in each group) based on RN concentrations added to 1mL acrylic monomer (0 for control, 256, 512, and 1024μg/mL). Flexural strength was assessed in megapascal (MPa) using a universal testing machine. Data analysis involved nonparametric Kruskal-Wallis analysis of variance and pairwise post-hoc Dunn's test.

RESULTS

The flexural strength decreased as the concentration of RNPs increased, with the lowest value observed at 1024μg/mL (63.06±5.33MPa). The control group exhibited the highest mean of flexural strength (88.43±4.41MPa), followed by the groups with RNPs at the concentrations of 256μg/mL (82.69±4.41MPa) and 512μg/mL (76.02±4.59MPa).

CONCLUSION

In conclusion, the addition of RNs to orthodontic acrylic resin had a dose-dependent impact on its flexural strength. Based on the findings, we recommend incorporating RNs at a concentration of 256μg/mL as an antimicrobial agent in orthodontic acrylic resin. However, further research is necessary to assess the long-term effects and clinical applications of this approach.

Progress of Antimicrobial Mechanisms of Stilbenoids

Antimicrobial drugs have made outstanding contributions to the treatment of pathogenic infections. However, the emergence of drug resistance continues to be a major threat to human health in recent years, and therefore, the search for novel antimicrobial drugs is particularly urgent. With a deeper understanding of microbial habits and drug resistance mechanisms, various creative strategies for the development of novel antibiotics have been proposed. Stilbenoids, characterized by a C6-C2-C6 carbon skeleton, have recently been widely recognized for their flexible antimicrobial roles. Here, we comprehensively summarize the mode of action of stilbenoids from the viewpoint of their direct antimicrobial properties, antibiofilm and antivirulence activities and their role in reversing drug resistance. This review will provide an important reference for the future development and research into the mechanisms of stilbenoids as antimicrobial agents.

Antifungal activity and mechanism of oxanthromicin against Verticillium dahliae

Oxanthromicin is an anthranone-type natural product isolated from Streptomyces sp. TRM 15522, which exhibits antifungal activity. However, the underlying mechanisms remain unclear. This study, therefore, aimed at investigating the mode of action of oxanthromicin against the phytopathogen Verticillium dahliae. We found that oxanthromicin substantially suppressed spore germination and mycelial growth in V. dahliae. Further, electron microscopy and staining with propidium iodide and Rhodamine 123 indicated that oxanthromicin causes cell membrane damage and induces changes in mitochondrial membrane potential. These findings suggest that oxanthromicin exhibits its antifungal activity by damaging fungal cell membranes. This discovery could potentially facilitate the development of oxanthromicin as a biological pesticide.

Specifically Targeting Metacaspases of Candida: A New Therapeutic Opportunity

The World Health Organization (WHO) recently published a list of fungal priority pathogens, including Candida albicans and C. auris. The increased level of resistance of Candida is raising concern, considering the availability of only four classes of medicine. The WHO is seeking novel agent classes with different targets and mechanisms of action. Targeting Candida metacaspases to control intrinsic cell death could provide new therapeutic opportunities for invasive candidiasis. In this review, we provide the available evidence for Candida cell death, describe Candida metacaspases, and discuss the potential of Candida metacaspases to offer a new specific target. Targeting Candida cell death has good scientific rationale given that the fungicidal activity of many marketed antifungals is mediated, among others, by cell death triggering. But none of the available antifungals are specifically activating Candida metacaspases, making this target a new therapeutic opportunity for non-susceptible isolates. It is expected that antifungals based on the activation of fungi metacaspases will have a broad spectrum of action, as metacaspases have been described in many fungi, including filamentous fungi. Considering this original mechanism of action, it could be of great interest to combine these new antifungal candidates with existing antifungals. This approach would help to avoid the development of antifungal resistance, which is especially increasing in Candida.

Comprehensive review of resveratrol as a feed additive in dairy cows: exploring its potential diverse effects and implications

Heat stress and growing demand for dairy products in tropical regions exert metabolic pressure on dairy cows, leading to metabolic diseases and economic losses. Resveratrol (RSV) is known for its numerous beneficial health effects and can be used as a barrier against metabolic abnormalities and prevent economic losses. Several studies have investigated the effects of RSV in humans and various animal species. In this review, we attempted to investigate the effects of RSV from different aspects so that we could have a practical proposal for its utilization in dairy cows. RSV was found to have potential antioxidant, anti-inflammatory, anti-obesity, and antimicrobial effects, leading to improved reproductive performance. It is interesting that the effect of RSV on the microbial population leads to a significant decrease in methane emissions. However, high doses of RSV have been associated with possible adverse effects, underscoring the dose dependence of its efficacy. In conclusion, RSV polyphenol at optimal doses is a promising agent for the prevention and treatment of metabolic abnormalities in dairy cows, based on our literature review and study results.

Anti-multispecies microbial biofilms and anti-inflammatory effects of antimicrobial photo-sonodynamic therapy based on acrylic resin containing nano-resveratrol

BACKGROUND

Polymethylmethacrylate (PMMA)-based removable orthodontic appliances are susceptible to microbial colonization due to the surface porosity, and accumulating the biofilms causes denture stomatitis. the present study evaluated the anti-biofilm and antiinflammatory effects of antimicrobial photo-sonodynamic therapy (aPSDT) against multispecies microbial biofilms (Candida albicans, Staphylococcus aureus, Streptococcus sobrinus, and Actinomyces naeslundii) formed on acrylic resin modified with nanoresveratrol (NR).

MATERIALS AND METHODS

Following the determination of the minimum biofilm inhibitory concentration (MBIC) of NR, in vitro anti-biofilm activity of NR was evaluated. The antibiofilm efficacy against multispecies microbial biofilm including C. albicans, S. aureus, S. sobrinus, and A. naeslundii, were assessed by biofilm inhibition test and the results were measured. To reveal the anti-inflammatory effects of aPSDT on human gingival fibroblast (HGF) cells, the gene expression levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were evaluated via quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

According to the results, the MBIC dose of NR against multispecies microbial biofilm was considered 512 µg/mL. The highest biofilm reduction activity was observed in MBIC treated with aPSDT and 2 × MBIC exposed to light emitting diode (LED) and ultrasound waves (UW). The expression level of TNF-α and IL-6 genes were significantly increased when HGF cells were exposed to multispecies microbial biofilms (P<0.05), while after treatment with aPSDT, the expression levels of genes were significantly downregulated in all groups (P<0.05).

CONCLUSION

Overall, NR-mediated aPSDT reduced the growth of the multispecies microbial biofilm and downregulated the expression of TNF-α and IL-6 genes. Therefore, modified PMMA with NR can be serving as a promising new orthodontic acrylic resin against multispecies microbial biofilms and the effect of this new material is amplified when exposed to LED and UW.

Recent Progress in Research on Mitochondrion-Targeted Antifungal Drugs: a Review

Fungal infections, which commonly occur in immunocompromised patients, can cause high morbidity and mortality. Antifungal agents act by disrupting the cell membrane, inhibiting nucleic acid synthesis and function, or inhibiting β-1,3-glucan synthase. Because the incidences of life-threatening fungal infections and antifungal drug resistance are continuously increasing, there is an urgent need for the development of new antifungal agents with novel mechanisms of action. Recent studies have focused on mitochondrial components as potential therapeutic drug targets, owing to their important roles in fungal viability and pathogenesis. In this review, we discuss novel antifungal drugs targeting mitochondrial components and highlight the unique fungal proteins involved in the electron transport chain, which is useful for investigating selective antifungal targets. Finally, we comprehensively summarize the efficacy and safety of lead compounds in clinical and preclinical development. Although fungus-specific proteins in the mitochondrion are involved in various processes, the majority of the antifungal agents target dysfunction of mitochondria, including mitochondrial respiration disturbance, increased intracellular ATP, reactive oxygen species generation, and others. Moreover, only a few drugs are under clinical trials, necessitating further exploration of possible targets and development of effective antifungal agents. The unique chemical structures and targets of these compounds will provide valuable hints for further exploiting new antifungals.

First Terbinafine-Resistant Trichophyton indotineae Isolates with Phe397Leu and/or Thr414His Mutations in Turkey

Fungal infections of the skin, nails, and hair caused by dermatophyte species continue to be a worldwide concern. The increase in terbinafine-resistant superficial dermatophytosis has become a major concern over the last decade. In this report, we presented two cases of infection with terbinafine-resistant Trichophyton indotineae, the first diagnosis of this species in Turkey. One patient exhibited erythematous pruritic patches and plaques in the inguinal and gluteal regions, while the other patient showed annular erythematous scaly plaques in the bilateral posterior thigh and gluteal regions. One patient harbored a CD36 mutation. Both strains harbored the same amino acid substitution in the squalene epoxidase gene, whereas one isolate had another unknown mutation. Clinical improvement was observed with resveratrol treatment in the patient with the CD36 mutation but not in the other patient.

Antioxidant-polyphenols of saw palmetto seeds: statistical optimized production and improved functional properties under solid-state fermentation by Trichoderma reesei

Saw palmetto seeds (SPS) contain essential phenolic compounds that provide antioxidant, antimicrobial, anti-inflammatory, and anti-diabetic benefits when added to food. Maximized/improved production of these valuable phenolic compounds is the main purpose of this study. Solid-state fermentation (SSF) is a promising processing technique that positively alters the levels of health-promoting compounds in plants and plant residues. Here, a central composite design matrix (16 runs) and response surface methodology were experimentally applied to investigate the best SSF conditions and their interactions for maximum production of phenolic compounds from SPS. A good correlation between actual and expected results was observed with higher multiple coefficients (R2 ~ 0.93–0.97) and strongly significant P values (< 0.0001) proving the accuracy of the statistical model/design. Under optimized SSF conditions, temperature 30 °C, moisture 10%, pH 7.0, and fermentation time 6 days, the total phenolic content and total antioxidant activity of SPS were maximized by 11-fold and 46–49 folds, respectively. According to HPLC analysis, the contents of all identifying polyphenols were 3.3–30.0 times greater in fermented SPS extract (FSPS) than in the unfermented SPS extract (UFSPS). The FSPS extract also contained four new/additional polyphenols (vanillic, p-coumaric, cinnamic, and quercetin). FSPS extract demonstrated much greater antibacterial and antifungal activities than UFSPS extract against various human pathogenic bacteria and fungi. Consequently, the FSPS-phenolic compounds can be exploited as a food supplement and an antimicrobial remedy.

Synergistic activity of pomegranate rind extract and Zn (II) against Candida albicans under planktonic and biofilm conditions, and a mechanistic insight based upon intracellular ROS induction

Candida albicans (C. albicans) is an opportunistic pathogen, which causes superficial infection and can lead to mortal systemic infections, especially in immunocompromised patients. The incidence of C. albicans infections is increasing and there are a limited number of antifungal drugs used in treatment. Therefore, there is an urgent need for new and alternative antifungal drugs. Pomegranate rind extract (PRE) is known for its broad-spectrum antimicrobial activities, including against C. albicans and recently, PRE and Zn (II) have been shown to induce synergistic antimicrobial activity against various microbes. In this study, the inhibitory activities of PRE, Zn (II) and PRE in combination with Zn (II) were evaluated against C. albicans. Antifungal activities of PRE and Zn (II) were evaluated using conventional microdilution methods and the interaction between these compounds was assessed by in vitro checkerboard and time kill assays in planktonic cultures. The anti-biofilm activities of PRE, Zn (II) and PRE in combination with Zn (II) were assessed using confocal laser scanning microscopy, with quantitative analysis of biofilm biomass and mean thickness analysed using COMSTAT2 analysis. In addition, antimicrobial interactions between PRE and Zn (II) were assayed in terms reactive oxygen species (ROS) production by C. albicans. PRE and Zn (II) showed a potent antifungal activity against C. albicans, with MIC values of 4 mg/mL and 1.8 mg/mL, respectively. PRE and Zn (II) in combination exerted a synergistic antifungal effect, as confirmed by the checkerboard and time kill assays. PRE, Zn (II) and PRE and Zn (II) in combination gave rise to significant reductions in biofilm biomass, although only PRE caused a significant reduction in mean biofilm thickness. The PRE and Zn (II) in combination caused the highest levels of ROS production by C. albicans, in both planktonic and biofilm forms. The induction of excess ROS accumulation in C. albicans may help explain the synergistic activity of PRE and Zn (II) in combination against C. albicans in both planktonic and biofilm forms. Moreover, the data support the potential of the PRE and Zn (II) combination as a novel potential anti-Candida therapeutic system.

Natural Products-Based Metallic Nanoparticles as Antimicrobial Agents

Natural products offer a wide range of bioactivity including antimicrobial properties. There are many reports showing the antimicrobial activities of phytochem icals from plants. However, the bioactivity is limited due to multidrug resistant properties of the microorganism and different composition of cell membrane. The antibacterial activity of the natural products is different toward Gram-negative and Gram-positive bacteria. These phenomena are caused by improper physicochemical conditions of the substance which hinder the phytochemical bioactivity against the broad range of bacteria. One of the strategies to improve the antimicrobial action is by biogenic synthesis via redox balance of the antimicrobial active substance with metal to form nanosized materials or nanoparticles (NPs). Antibiotic resistance is not relevant to NPs because the action of NPs is via direct contact with bacterial cell walls without the need of penetration into microbial cells. The NPs that have shown their effectiveness in preventing or overcoming biofilm formation such as silver-based nanoparticles (AgNPs), gold-based nanoparticles (AuNPs), platinum-based nanoparticles (PtNPs) and Zinc oxide-based nanoparticles (ZnONPs). Due to its considerably simple synthesis procedure has encouraged researchers to explore antimicrobial potency of metallic nanoparticles. Those metallic nanoparticles remarkably express synergistic effects against the microorganisms tested by affecting bacterial redox balance, thus disrupting their homeostasis. In this paper, we discuss the type of metallic nanoparticle which have been used to improve the antimicrobial activity of plant extract/constituents, preparation or synthesis process and characterisation of the plant-based metallic nanoparticles.

Resveratrol in Intestinal Health and Disease: Focusing on Intestinal Barrier

The integrity of intestinal barrier determines intestinal homeostasis, which could be affected by various factors, like physical, chemical, and biological stimuli. Therefore, it is of considerable interest and importance to maintain intestinal barrier function. Fortunately, many plant polyphenols, including resveratrol, could affect the health of intestinal barrier. Resveratrol has many biological functions, such as antioxidant, anti-inflammation, anti-tumor, and anti-cardiovascular diseases. Accumulating studies have shown that resveratrol affects intestinal tight junction, microbial composition, and inflammation. In this review, we summarize the effects of resveratrol on intestinal barriers as well as the potential mechanisms (e.g., inhibiting the growth of pathogenic bacteria and fungi, regulating the expression of tight junction proteins, and increasing anti-inflammatory T cells while reducing pro-inflammatory T cells), and highlight the applications of resveratrol in ameliorating various intestinal diseases.

Composition and Biological Activity of Vitis vinifera Winter Cane Extract on Candida Biofilm

Vitis vinifera canes are waste material of grapevine pruning and thus represent cheap source of high-value polyphenols. In view of the fact that resistance of many pathogenic microorganisms to antibiotics is a growing problem, the antimicrobial activity of plant polyphenols is studied as one of the possible approaches. We have investigated the total phenolic content, composition, antioxidant activity, and antifungal activity against Candida biofilm of an extract from winter canes and a commercially available extract from blue grapes. Light microscopy and confocal microscopy imaging as well as crystal violet staining were used to quantify and visualize the biofilm. We found a decrease in cell adhesion to the surface depending on the concentration of resveratrol in the cane extract. The biofilm formation was observed as metabolic activity of Candida albicans, Candida parapsilosis and Candida krusei biofilm cells and the minimum biofilm inhibitory concentrations were determined. The highest inhibition of metabolic activity was observed in Candida albicans biofilm after treatment with the cane extract (30 mg/L) and blue grape extract (50 mg/L). The composition of cane extract was analyzed and found to be comparatively different from blue grape extract. In addition, the content of total phenolic groups in cane extract was three-times higher (12.75 g_GA/L). The results showed that cane extract was more effective in preventing biofilm formation than blue grape extract and winter canes have proven to be a potential source of polyphenols for antimicrobial and antibiofilm treatment.

Natural Compounds With Antimicrobial and Antiviral Effect and Nanocarriers Used for Their Transportation

Due to the increasing prevalence of life-threatening bacterial, fungal and viral infections and the ability of these human pathogens to develop resistance to current treatment strategies, there is a great need to find and develop new compunds to combat them. These molecules must have low toxicity, specific activity and high bioavailability. The most suitable compounds for this task are usually derived from natural sources (animal, plant or even microbial). In this review article, the latest and most promising natural compounds used to combat bacteria, filamentous fungi and viruses are presented and evaluated. These include plant extracts, essential oils, small antimicrobial peptides of animal origin, bacteriocins and various groups of plant compounds (triterpenoids; alkaloids; phenols; flavonoids) with antimicrobial and antiviral activity. Data are presented on the inhibitory activity of each natural antimicrobial substance and on the putative mechanism of action against bacterial and fungal strains. The results show that among the bioactive compounds studied, triterpenoids have significant inhibitory activity against coronaviruses, but flavonoids have also been shown to inhibit SARS-COV-2. The last chapter is devoted to nanocarriers used to improve stability, bioavailability, cellular uptake/internalization, pharmacokinetic profile and reduce toxicity of natural compunds. There are a number of nanocarriers such as liposomes, drug delivery microemulsion systems, nanocapsules, solid lipid nanoparticles, polymeric micelles, dendrimers, etc. However, some of the recent studies have focused on the incorporation of natural substances with antimicrobial/antiviral activity into polymeric nanoparticles, niosomes and silver nanoparticles (which have been shown to have intrinsic antimicrobial activity). The natural antimicrobials isolated from animals and microorganisms have been shown to have good inhibitory effect on a range of pathogens, however the plants remain the most prolific source. Even if the majority of the studies for the biological activity evaluation are in silico or in vitro, their internalization in the optimum nanocarriers represents the future of “green therapeutics” as shown by some of the recent work in the field.

Antifungal Activity of the Extract of a Macroalgae, Gracilariopsis persica, against Four Plant Pathogenic Fungi

Nowadays, the extract of seaweeds has drawn attention as a rich source of bioactive metabolites. Seaweeds are known for their biologically active compounds whose antibacterial and antifungal activities have been documented. This research aimed to study the profile of phenolic compounds using the HPLC method and determine biologically active compounds using the GC-MS method and the antifungal activity of Gracilariopsis persica against plant pathogenic fungi. G. persica was collected from its natural habitat in Suru of Bandar Abbas, Iran, dried, and extracted by methanol. The quantitative results on phenolic compounds using the HPLC method showed that the most abundant compounds in G. persica were rosmarinic acid (20.9 ± 0.41 mg/kg DW) and quercetin (11.21 ± 0.20 mg/kg DW), and the least abundant was cinnamic acid (1.4 ± 0.10 mg/kg DW). The GC-MS chromatography revealed 50 peaks in the methanolic extract of G. persica, implying 50 compounds. The most abundant components included cholest-5-en-3-ol (3 beta) (27.64%), palmitic acid (17.11%), heptadecane (7.71%), and palmitic acid methyl ester (6.66%). The antifungal activity of different concentrations of the extract was determined in vitro. The results as to the effect of the alga extract at the rates of 200, 400, 600, 800, and 1000 μL on the mycelial growth of four important plant pathogenic fungi, including Botrytis cinerea, Aspergillus niger, Penicillium expansum, and Pyricularia oryzae, revealed that the mycelial growth of all four fungi was lower at higher concentrations of the alga extract. However, the extract concentration of 1000 μL completely inhibited their mycelial growth. The antifungal activity of this alga may be related to the phenolic compounds, e.g., rosmarinic acid and quercetin, as well as compounds such as palmitic acid, oleic acid, and other components identified using the GC-MS method whose antifungal effects have already been confirmed.

Recent progress on anti-Candida natural products

Candida is an intractable life-threatening pathogen. Candida infection is extremely difficult to eradicate, and thus is the major cause of morbidity and mortality in immunocompromised individuals. Morevover, the rapid spread of drug-resistant fungi has led to significant decreases in the therapeutic effects of clinical drugs. New anti-Candida agents are urgently needed to solve the complicated medical problem. Natural products with intricate structures have attracted great attention of researchers who make every endeavor to discover leading compounds for antifungal agents. Their novel mechanisms and diverse modes of action expand the variety of fungistatic agents and reduce the emergence of drug resistance. In recent decades, considerable effort has been devoted to finding unique antifungal agents from nature and revealing their unusual mechanisms, which results in important progress on the development of new antifungals, such as the novel cell wall inhibitors YW3548 and SCY-078 which are being tested in clinical trials. This review will present a brief summary on the landscape of anti-Candida natural products within the last decade. We will also discuss in-depth the research progress on diverse natural fungistatic agents along with their novel mechanisms.

In vitro antibiofilm activity of resveratrol against avian pathogenic Escherichia coli

BACKGROUND

Avian pathogenic Escherichia coli (APEC) strains cause infectious diseases in poultry. Resveratrol is extracted from Polygonum cuspidatum, Cassia tora Linn and Vitis vinifera, and displays good antimicrobial activity. The present study aimed to investigate the antibiofilm effect of resveratrol on APEC in vitro. The minimum inhibitory concentration (MIC) of resveratrol and the antibiotic florfenicol toward APEC were detected using the broth microdilution method. Then, the effect of resveratrol on swimming and swarming motility was investigated using a semisolid medium culture method. Subsequently, the minimum biofilm inhibitory concentration (MBIC) and the biofilm eradication rate were evaluated using crystal violet staining. Finally, the antibiofilm activity of resveratrol was observed using scanning electron microscopy (SEM). Meanwhile, the effects of florfenicol combined with resveratrol against biofilm formation by APEC were evaluated using optical microscopy (OM) and a confocal laser scanning microscopy (CLSM).

RESULTS

The MICs of resveratrol and florfenicol toward APEC were 128 μg/mL and 64 μg/mL, respectively. The swimming and swarming motility abilities of APEC were inhibited in a resveratrol dose-dependent manner. Furthermore, resveratrol showed a significant inhibitory activity against APEC biofilm formation at concentrations above 1 μg/mL (p < 0.01). Meanwhile, the inhibitory effect of resveratrol at 32 μg/mL on biofilm formation was observed using SEM. The APEC biofilm was eradicated at 32 μg/mL of resveratrol combined with 64 μg/mL of florfenicol, which was observed using CLSM and OM. Florfenicol had a slight eradication effect of biofilm formation, whereas resveratrol had a strong biofilm eradication effect toward APEC.

CONCLUSION

Resveratrol displayed good antibiofilm activity against APEC in vitro, including inhibition of swimming and swarming motility, biofilm formation, and could eradicate the biofilm.

Dexmedetomidine reduces the apoptosis of rat hippocampal neurons via mediating ERK1/2 signal pathway by targeting miR-155

Rat hippocampal neurons were isolated and divided into Normal, oxygen glucose deprivation/reoxygenation (OGD/R), OGD/R + DEX, OGD/R + NC mimic, OGD/R + miR-155 mimic and OGD/R + DEX + miR-155 mimic groups. In OGD/R group, LDH, ROS and MDA levels and apoptosis rate was increased, with up-regulations of miR-155, Cyt c and Bax/Bcl-2 ratio, but decreases of SOD, GSH-Px and MMP levels, as well as down-regulations of p-ERK1/2/ERK1/2. As compared to the OGD/R group, parameters above in the OGD/R + DEX group were ameliorated evidently, while OGD/R + miR-155 mimic group manifested the opposite changes. Besides, miR-155 mimic could abolish the protective effect of DEX on the hippocampal neurons under OGD/R. DEX, via down-regulating the expression of miR-155, could activate the ERK1/2 pathway, thereby mitigating the apoptosis and oxidative stress injury and increasing the MMP, thereby protecting hippocampal cells from OGD/R injury.

Mechanistic Understanding of Candida albicans Biofilm Formation and Approaches for Its Inhibition

In recent years, the demand for novel antifungal therapies has increased several- folds due to its potential to treat severe biofilm-associated infections. Biofilms are made by the sessile microorganisms attached to the abiotic or biotic surfaces, enclosed in a matrix of exopolymeric substances. This results in new phenotypic characteristics and intrinsic resistance from both host immune response and antimicrobial drugs. Candida albicans biofilm is a complex association of hyphal cells that are associated with both abiotic and animal tissues. It is an invasive fungal infection and acts as an important virulent factor. The challenges linked with biofilm-associated diseases have urged scientists to uncover the factors responsible for the formation and maturation of biofilm. Several strategies have been developed that could be adopted to eradicate biofilm-associated infections. This article presents an overview of the role of C. albicans biofilm in its pathogenicity, challenges it poses and threats associated with its formation. Further, it discusses strategies that are currently available or under development targeting prostaglandins, quorum-sensing, changing surface properties of biomedical devices, natural scaffolds, and small molecule-based chemical approaches to combat the threat of C. albicans biofilm. This review also highlights the recent developments in finding ways to increase the penetration of drugs into the extracellular matrix of biofilm using different nanomaterials against C. albicans.

Inhibitory activity of stilbenes against filamentous fungi

Stilbenoids (resveratrol and its derivatives) are secondary metabolites produced by plants as defence mechanism to microbial infection. These compounds are known for their anti-inflammatory action and health benefits in preventing a wide range of disorders (e.g. cancer and cardiovascular diseases). However, their antimicrobial properties are less investigated. A series of 8 stilbenoid compounds were synthesized and their antifungal activity against 19 wild strains of filamentous fungi and yeasts (isolated from the environment and food) was tested in vitro. Using an agar diffusion assay, compounds were tested at the concentration of 100 μg/ml on filamentous fungi and yeasts at 10⁴ CFU/ml. The results showed that tested derivatives possess moderate antifungal activity: in particular, monomeric stilbenoids 3'-hydroxy-pterostilbene and piceatannol, and dimeric stilbenoids (±)-trans-δ-viniferin and pallidol were active against mycotoxigenic fungi.

A Comprehensive Study on the Antimicrobial Properties of Resveratrol as an Alternative Therapy

Resveratrol is a polyphenolic antioxidant whose possible health benefits include anticarcinogenic, antiaging, and antimicrobial properties that have gained significant attention. The compound is well accepted by individuals and has been commonly used as a nutraceutical in recent decades. Its widespread usage makes it essential to study as a single agent as well as in combination with traditional prescription antibiotics as regards to antimicrobial properties. Resveratrol demonstrates the action of antimicrobials against a remarkable bacterial diversity, viruses, and fungus. This report explains resveratrol as an all-natural antimicrobial representative. It may modify the bacterial virulence qualities resulting in decreased toxic substance production, biofilm inhibition, motility reduction, and quorum sensing disturbance. Moreover, in conjunction with standard antibiotics, resveratrol improves aminoglycoside efficacy versus Staphylococcus aureus, while it antagonizes the deadly function of fluoroquinolones against S. aureus and also Escherichia coli. The present study aimed to thoroughly review and study the antimicrobial potency of resveratrol, expected to help researchers pave the way for solving antimicrobial resistance.

Reactive oxygen mediated apoptosis as a therapeutic approach against opportunistic Candida albicans

Candida albicans are polymorphic fungal species commonly occurs in a symbiotic association with the host's usual microflora. Certain specific changes in its usual microenvironment can lead to diseases ranging from external mucosal to severally lethal systemic infections like invasive candidiasis hospital-acquired fatal infection caused by different species of Candida. The patient acquired with this infection has a high mortality and morbidity rate, ranging from 40% to 60%. This is an ill-posed problem by its very nature. Hence, early diagnosis and management is a crucial part. Antifungal drug resistance against the first and second generation of antifungal drugs has made it difficult to treat such fatal diseases. After a few dormant years, recently, there has been a rapid turnover of identifying novel drugs with low toxicity to limit the problem of drug resistance. After an initial overview of related work, we examine specific prior work on how a change in oxidative stress can facilitate apoptosis in C. albicans. Subsequently, it was investigated that Candida spp. suppresses the production of ROS mediated host defense system. Here, we have reviewed possibly all the small molecule inhibitors, natural products, antimicrobial peptide, and some naturally derived semi-synthetic compounds which are known to influence oxidative stress, to generate a proper apoptotic response in C. albicans and thus might be a novel therapeutic approach to augment the current treatment options.

Antifungal Activity of Phenolic and Polyphenolic Compounds from Different Matrices of Vitis vinifera L. against Human Pathogens

Phenolic compounds, the most widely distributed class of natural products in the plants, show several biological properties including antifungal activity. Phenolics contained in grapes can be classified in two main groups, flavonoids and non-flavonoids compounds. Variability and yield extraction of phenolic and polyphenolic compounds from different matrices of Vitis vinifera depends of cultivar, climate, soil condition and process technology. Unripe grapes, berry skins and seeds, leaves, canes and stems and not-fermented and fermented pomaces represent large reusable and valuable wastes from agricultural and agro-industrial processes. This review summarizes studies that examine the extraction method, chemical characterization, and antifungal activity of phenolic and polyphenolic compounds from edible and non-edible V. vinifera matrices against human fungal pathogens. In the world, around one billion people have fungal diseases related to skin, nail or hair and around 150 million have systemic diseases caused by fungi. Few studies on antifungal activity of plant extracts have been performed. This review provides useful information for the application of V. vinifera phenolics in the field of antifungals for human use.

Mezoneuron benthamianum inhibits cell adherence, hyphae formation, and phospholipase production in Candida albicans

The aim of this study was to evaluate the phytochemical constituents, antioxidant, antifungal, and anti-virulence activities of traditionally used Mezoneuron benthamianum leaves. Extracts were prepared using acetone and methanol, and the preliminary phytochemical screening was performed. The antioxidant activity was studied using the DPPH method. Anti-Candida albicans activity was established and the effect on the germ tube and phospholipase production, as well as on the host cell adherence was assessed. The extracts showed the presence of anthraquinones, cardiac glycosides, flavonoids, reducing sugars, saponins, steroids, tannins, and terpenoids. Gallic acid and trans-resveratrol were among the predominant phytochemicals found in M. benthamianum. The crude extracts presented significantly higher antioxidant activity than the ascorbic acid standard. At 0.39 mg/mL, acetone extract inhibited the growth of Candida albicans. At lower concentrations (200-50 µg/mL), it significantly inhibited the adherence ability (up to 51%), formation of hyphae (up to 65%), and the production of phospholipase. In conclusion, at high concentrations, M. benthamianum kills C. albicans, and at lower concentrations, it can inhibit the virulence properties of this pathogen. This study on crude extract validates the traditional use of this plant. However, further research is required to establish the anti-virulence activity of the two compounds and their therapeutic potential.

Plant Phytochemicals in Food Preservation: Antifungal Bioactivity: A Review

Synthetic food additives generate a negative perception in consumers. This fact generates an important pressure on food manufacturers, searching for safer natural alternatives. Phytochemicals (such as polyphenols and thiols) and plant essential oils (terpenoids) possess antimicrobial activities that are able to prevent food spoilage due to fungi (e.g., Aspergillus, Penicillium) and intoxications (due to mycotoxins), both of which are important economic and health problems worldwide. This review summarizes industrially interesting antifungal bioactivities from the three main types of plant nutraceuticals: terpenoids (as thymol), polyphenols (as resveratrol) and thiols (as allicin) as well as some of the mechanisms of action. These phytochemicals are widely distributed in fruits and vegetables and are very useful in food preservation as they inhibit growth of important spoilage and pathogenic fungi, affecting especially mycelial growth and germination. Terpenoids and essential oils are the most abundant group of secondary metabolites found in plant extracts, especially in common aromatic plants, but polyphenols are a more remarkable group of bioactive compounds as they show a broad array of bioactivities.

Probiotics as antifungal agents: Experimental confirmation and future prospects

Fungal burden throughout the world is very high and it keeps escalating due to increasing numbers of immunocompromised individuals. In contrast, the drugs used in management of fungal infections are so few some with high toxicity. Furthermore, highly resistant fungal pathogens are emerging for example Candida auris, Candida glabrata, Candida gullemondii and Aspergillus species among others. Thus now, more than ever, there is a need for combined efforts and an all round search for possible solutions to curb these problems. Therefore, the role of probiotics in management of fungal infections is indispensable. In fact, the antimicrobial activity of probiotics has been screened with promising results against microbial pathogens. Although, recent reports indicated that probiotics may also contribute to protect against fungal infections, the research done in checking antifungal activity of probiotics has used varied technology. This calls for harmonization of the methods used to screen and confirm the antimicrobial activity of probiotics and other candidate microorganisms. We therefore sought to address issues of disparity in probiotic research and their outcomes. Thus this paper is in order as it comprehensively reviews' publications, provides a summary of the methods and future prospects of probiotics as antifungal agents.

Hydrophilic Linear Peptide with Histidine and Lysine Residues as a Key Factor Affecting Antifungal Activity

Increases in the numbers of immunocompromised patients and the emergence of drug-resistance fungal pathogens have led to the need for new, safe, efficacious antifungal agents. In this study, we designed a histidine-lysine-lysine (HKK) motif and synthesized six HKK peptides with repetitions of the motif. These peptides showed length-dependent antifungal activity against drug-susceptible and drug-resistant fungal pathogens via membranolytic or non-membranolytic action. None of the peptides were cytotoxic to rat erythrocytes or NIH3T3 mouse embryonic fibroblasts. Short-length peptides were directly translocated in fungal cytosol and reacted with mitochondria, resulting in apoptosis. Membrane-permeabilizing activity occurred in the presence of long peptides, and peptides were able to transfer to the cytosol and induce reactive oxygen species. Our results suggest that peptides composed only of cationic amino acids may be good candidates as antifungal agents.

Effect of resveratrol and Regrapex-R-forte on Trichosporon cutaneum biofilm

Microorganisms that cause chronic infections exist predominantly as surface-attached stable communities known as biofilms. Microbial cells in biofilms are highly resistant to conventional antibiotics and other forms of antimicrobial treatment; therefore, modern medicine tries to develop new drugs that exhibit anti-biofilm activity. We investigated the influence of a plant polyphenolic compound resveratrol (representative of the stilbene family) on the opportunistic pathogen Trichosporon cutaneum. Besides the influence on the planktonic cells of T. cutaneum, the ability to inhibit biofilm formation and to eradicate mature biofilm was studied. We have tested resveratrol as pure compound, as well as resveratrol in complex plant extract-the commercially available dietary supplement Regrapex-R-forte, which contains the extract of Vitis vinifera grape and extract of Polygonum cuspidatum root. Regrapex-R-forte is rich in stilbenes and other biologically active substances. Light microscopy imaging, confocal microscopy, and crystal violet staining were used to quantify and visualize the biofilm. The metabolic activity of biofilm-forming cells was studied by the tetrazolium salt assay. Amphotericin B had higher activity against planktonic cells; however, resveratrol and Regrapex-R-forte showed anti-biofilm effects, both in inhibition of biofilm formation and in the eradication of mature biofilm. The minimum biofilm eradicating concentration (MBEC₈₀) for Regrapex-R-forte was found to be 2222 mg/L (in which resveratrol concentration is 200 mg/L). These methods demonstrated that Regrapex-R-forte can be employed as an anti-biofilm agent, as it has similar effect as amphotericin B (MBEC₈₀ = 700 mg/L), which is routinely used in clinical practice.

Oxyresveratrol-induced DNA cleavage triggers apoptotic response in Candida albicans

Oxyresveratrol is a naturally occurring phytoalexin produced by plants in response to infection. Biological activities of oxyresveratrol have been studied such as antioxidant, anticancer and anti-inflammation. However, further antimicrobial activity and its mechanism need to be investigated. This study exhibited growth inhibition against pathogenic fungi and investigated its mode of action. Oxyresveratrol inflicted cleavage on DNA, leading to G2/M phase arrest. DNA damage by oxyresveratrol was not the result of oxidative stress but it was triggered by direct binding to DNA. Oxyresveratrol-treated cells showed an apoptotic pathway characterized by phosphatidylserine exposure, apoptotic volume decrease and metacaspase activation. Mitochondria-associated apoptotic features also appeared. Oxyresveratrol-induced Ca²⁺ overload led to mitochondrial membrane depolarization and release of cytochrome c from mitochondria to cytosol. In conclusion, oxyresveratrol with DNA-binding affinity induces DNA cleavage, and eventually leads to mitochondria-mediated apoptosis in Candida albicans.

Comprehensive review on the antimicrobial potency of the plant polyphenol Resveratrol

Treatment of some infectious diseases are becoming more complicated because of increasing drug resistance rate and lack of proper antibiotics. Because of the rapid increase in drug-resistance trend, there is an urgent need for alternative microbicides to control infectious diseases. Resveratrol (RSV) is a small plant polyphenol that is naturally produced and distributed in 72 particular families of plants. The usage of natural derivatives such as RSV, have become popular among researchers for curing acute and chronic diseases. The purpose of the preset study was to comprehensively review and survey the antimicrobial potency of RSV. The present study demonstrates RSV as a natural antimicrobial agent.

Synergistic Effects and Mechanisms of Budesonide in Combination with Fluconazole against Resistant Candida albicans

Candida albicans is an important opportunistic pathogen, causing both superficial mucosal infections and life-threatening systemic diseases in the clinic. The emergence of drug resistance in Candida albicans has become a noteworthy phenomenon due to the extensive use of antifungal agents and the development of biofilms. This study showed that budesonide potentiates the antifungal effect of fluconazole against fluconazole-resistant Candida albicans strains both in vitro and in vivo. In addition, our results demonstrated, for the first time, that the combination of fluconazole and budesonide can reverse the resistance of Candida albicans by inhibiting the function of drug transporters, reducing the formation of biofilms, promoting apoptosis and inhibiting the activity of extracellular phospholipases. This is the first study implicating the effects and mechanisms of budesonide against Candida albicans alone or in combination with fluconazole, which may ultimately lead to the identification of new potential antifungal targets.

Alteramide B is a microtubule antagonist of inhibiting Candida albicans

BACKGROUND

Alteramide B (ATB), isolated from Lysobacter enzymogenes C3, was a new polycyclic tetramate macrolactam (PTM). ATB exhibited potent inhibitory activity against several yeasts, particularly Candida albicans SC5314, but its antifungal mechanism is unknown.

METHODS

The structure of ATB was established by extensive spectroscopic analyses, including high-resolution mass spectrometry, 1D- and 2D-NMR, and CD spectra. Flow cytometry, fluorescence microscope, transmission electron microscope, molecular modeling, overexpression and site-directed mutation studies were employed to delineate the anti-Candida molecular mechanism of ATB.

RESULTS

ATB induced apoptosis in C. albicans through inducing reactive oxygen species (ROS) production by disrupting microtubules. Molecular dynamics studies revealed the binding patterns of ATB to the β-tubulin subunit. Overexpression of the wild type and site-directed mutants of the β-tubulin gene (TUBB) changed the sensitivity of C. albicans to ATB, confirming the binding of ATB to β-tubulin, and indicating that the binding sites are L215, L217, L273, L274 and R282. In vivo, ATB significantly improved the survival of the candidiasis mice and reduced fungal burden.

CONCLUSION

The molecular mechanism underlying the ATB-induced apoptosis in C. albicans is through inhibiting tubulin polymerization that leads to cell cycle arrest at the G2/M phase. The identification of ATB and the study of its activity provide novel mechanistic insights into the mode of action of PTMs against the human pathogen.

GENERAL SIGNIFICANCE

This study shows that ATB is a new microtubule inhibitor and a promising anti-Candida lead compound. The results also support β-tubulin as a potential target for anti-Candida drug discovery.

Exploiting mitochondria as targets for the development of new antifungals

Mitochondria are essential for cell growth and survival of most fungal pathogens. Energy (ATP) produced during oxidation/reduction reactions of the electron transport chain (ETC) Complexes I, III and IV (CI, CIII, CIV) fuel cell synthesis. The mitochondria of fungal pathogens are understudied even though more recent published data suggest critical functional assignments to fungal-specific proteins. Proteins of mammalian mitochondria are grouped into 16 functional categories. In this review, we focus upon 11 proteins from 5 of these categories in fungal pathogens, OXPHOS, protein import, stress response, carbon source metabolism, and fission/fusion morphology. As these proteins also are fungal-specific, we hypothesize that they may be exploited as targets in antifungal drug discovery. We also discuss published transcriptional profiling data of mitochondrial CI subunit protein mutants, in which we advance a novel concept those CI subunit proteins have both shared as well as specific responsibilities for providing ATP to cell processes.

HSAF-induced antifungal effects in Candida albicans through ROS-mediated apoptosis

Heat-stable antifungal factor (HSAF) belongs to polycyclic tetramate macrolactams (PTMs), which inhibits many fungal pathogens and is effective in inhibiting Candida albicans (C. albicans). In this study, we found that HSAF induced the apoptosis of Candida albicans SC5314 through inducing the production of reactive oxygen species (ROS). Nevertheless, we validated the efficacy of HSAF against candidiasis caused by C. albicans in a murine model in vivo, and HSAF significantly improved survival and reduced fungal burden compared to vehicles. A molecular dynamics (MD) simulation was also investigated, revealing the theoretical binding mode of HSAF to the β-tubulin of C. albicans. This study first found PTMs-induced fungal apoptosis through ROS accumulation in C. albicans and its potential as a novel agent for fungicides.