Synergism of antifungal activity between mitochondrial respiration inhibitors and kojic acid

Inhibition of Melanization by Kojic Acid Promotes Cell Wall Disruption of the Human Pathogenic Fungus Fonsecaea sp

Chromoblastomycosis (CBM) is a chronic human subcutaneous mycosis caused by various aetiologic agents. CBM does not have an established treatment but may be managed using antifungal agents, surgical removal of the lesions, or cryotherapy. Kojic acid (KA), a known tyrosinase inhibitor with a variety of biological actions, including fungistatic action against the fungus Cryptococcus neoformans, mediated by inhibiting melanin production, seems to be an alternative to improve the treatment of CBM. The aim of the present study was to analyze the action of KA against the pathogenic fungus Fonsecaea sp., an aetiological agent of CBM. The fungal culture was incubated with KA, and the amount of melanin was assessed, followed by cytochemical detection. Subsequently, the samples were analyzed by light microscopy, transmission and scanning electron microscopy. Culture analysis revealed that 100 g/mL KA significantly decreased the melanization of the fungus and the exocytosis of melanin into the culture supernatant. Additionally, KA induced less growth of biofilm formation and intense disruption of the cell wall, and decreased the number of melanin-containing vesicles in the culture supernatant. Finally, KA inhibited fungal filamentation in culture and the subsequent phagocytosis process. Thus, KA may be a promising substance to help in the treatment of CBM.

Fungal Infections as an Uprising Threat to Human Health: Chemosensitization of Fungal Pathogens With AFP From Aspergillus giganteus

Occurrence and intensity of systemic invasive fungal infections have significantly risen in recent decades with large amount of mortality and morbidity rates at global level. Treatment therapy lies on the current antifungal interventions and are often limited due to the emergence of resistance to antifungal agents. Chemosensitization of fungal strains to the conventional antimycotic drugs are of growing concern. Current antifungal drugs often have been reported with poor activity and side effects to the host and have a few number of targets to manifest their efficacy on the pathogens. Indiscriminately, the aforementioned issues have been easily resolved by the development of new intervention strategies. One such approach is to employ combinational therapy that has exhibited a great level of inhibitions than that of a single compound. Chemosensitization of pathogenic mycoses to commercial antifungal drugs could be drastically enhanced by co-application of chemosensitizers along with the conventional drugs. Chemosensitizers could address the resistance mechanisms evolved in the pathogenic fungi and targeting the system to make the organism susceptible to commercially and clinically proven antifungal drugs. However, this strategy has not been overreached to the greater level, but it needs much attention to fight against not only with the pathogen but combat the resistance mechanisms of pathogens to drugs. Natural compounds including plant compounds and microbial proteins act as potential chemosensitizers to break the resistance in mycoses. Aspergillus giganteus, a filamentous fungus, is known to produce a cysteine rich extracellular protein called as antifungal protein (AFP). AFP has shown enhanced efficacy against several filamentous and non-filamentous fungal pathogens. On the basis of the reported studies on its targeted potential against pathogenic mycoses, AFP would be fabricated as a good chemosensitizer to augment the fungicidal efficacy of commercial antimycotic drugs. This paper reviews on breakthrough in the discovery of antifungal drugs along with the resistance patterns of mycoses to commercial drugs followed by the current intervention strategies applied to augment the fungicidal potential of drugs.

Antifungal Activity and Biosynthetic Potential of New Streptomyces sp. MW-W600-10 Strain Isolated from Coal Mine Water

Crop infections by fungi lead to severe losses in food production and pose risks for human health. The increasing resistance of pathogens to fungicides has led to the higher usage of these chemicals, which burdens the environment and highlights the need to find novel natural biocontrol agents. Members of the genus Streptomyces are known to produce a plethora of bioactive compounds. Recently, researchers have turned to extreme and previously unexplored niches in the search for new strains with antimicrobial activities. One such niche are underground coal mine environments. We isolated the new Streptomyces sp. MW-W600-10 strain from coal mine water samples collected at 665 m below ground level. We examined the antifungal activity of the strain against plant pathogens Fusarium culmorum DSM62188 and Nigrospora oryzae roseF7. Furthermore, we analyzed the strain’s biosynthetic potential with the antiSMASH tool. The strain showed inhibitory activity against both fungi strains. Genome mining revealed that it has 39 BGCs, among which 13 did not show similarity to those in databases. Additionally, we examined the activity of the Streptomyces sp. S-2 strain isolated from black soot against F. culmorum DSM62188. These results show that coal-related strains could be a source of novel bioactive compounds. Future studies will elucidate their full biotechnological potential.

Sisters in structure but different in character, some benzaldehyde and cinnamaldehyde derivatives differentially tune Aspergillus flavus secondary metabolism

Great are the expectations for a new generation of antimicrobials, and strenuous are the research efforts towards the exploration of diverse molecular scaffolds-possibly of natural origin - aimed at the synthesis of new compounds against the spread of hazardous fungi. Also high but winding are the paths leading to the definition of biological targets specifically fitting the drug's structural characteristics. The present study is addressed to inspect differential biological behaviours of cinnamaldehyde and benzaldehyde thiosemicarbazone scaffolds, exploiting the secondary metabolism of the mycotoxigenic phytopathogen Aspergillus flavus. Interestingly, owing to modifications on the parent chemical scaffold, some thiosemicarbazones displayed an increased specificity against one or more developmental processes (conidia germination, aflatoxin biosynthesis, sclerotia production) of A. flavus biology. Through the comparative analysis of results, the ligand-based screening strategy here described has allowed us to delineate which modifications are more promising for distinct purposes: from the control of mycotoxins contamination in food and feed commodities, to the environmental management of microbial pathogens, to the investigation of specific structure-activity features for new generation drug discovery.

Effects of kojic acid on boar sperm quality and anti-bacterial activity during liquid preservation at 17 C

Bacteriospermia is a documented risk to sperm quality when boar semen is stored at 17 °C. The objective of this study was to evaluate the effects of kojic acid (KA) on sperm quality and anti-bacterial effect during liquid storage boar semen at 17 °C, as well as to explore sperm-oocyte binding and embryonic development in vitro. Boar semen was diluted with Beltsville thawing solution (BTS), and it contained KA at different concentrations (0, 0.02, 0.04, 0.06, 0.08, and 0.10 g/L). Bacterial concentrations and sperm quality parameters (motility, mitochondrial membrane potential, acrosome integrity, and plasma membrane integrity) were evaluated on each experimental day. Differences in microbial compositions were compared using 16S rDNA sequencing among the control group, 0.04 g/L KA, and 0.25 g/L gentamycin groups on experimental day 5, and the effects of KA on sperm capacitation, Western blot, total anti-oxidant capacity (T-AOC), reactive oxygen species (ROS) content, malondialdehyde (MDA) content, in vitro fertilization (IVF) parameters, sperm-oocyte binding, cleavage rates, and blastocyst rates were evaluated. The results showed that KA at the optimum concentration of 0.04 g/L significantly improved sperm quality parameters and sperm capacitation, increased T-AOC ability, enhanced IVF parameters and sperm-oocyte binding, increased cleavage and blastocyst rates, inhibited bacterial concentrations, reduced ROS and MDA content, and altered bacterial compositions (P < 0.05). Moreover, KA also increased the expression of anti-oxidant-related proteins, SOD1, SOD2 and CAT, and anti-apoptosis-related protein, Bcl 2, and decreased the expression of apoptosis-related proteins, caspase 3 and Bax in sperm (P < 0.05). These findings demonstrated that supplementation of antibiotic-free extenders for boar semen with 0.04 g/L KA has beneficial effects on liquid boar sperm preservation.

Sabotage at the Powerhouse? Unraveling the Molecular Target of 2-Isopropylbenzaldehyde Thiosemicarbazone, a Specific Inhibitor of Aflatoxin Biosynthesis and Sclerotia Development in Aspergillus flavus, Using Yeast as a Model System

Amongst the various approaches to contain aflatoxin contamination of feed and food commodities, the use of inhibitors of fungal growth and/or toxin biosynthesis is showing great promise for the implementation or the replacement of conventional pesticide-based strategies. Several inhibition mechanisms were found taking place at different levels in the biology of the aflatoxin-producing fungal species such as Aspergillus flavus: compounds that influence aflatoxin production may block the biosynthetic pathway through the direct control of genes belonging to the aflatoxin gene cluster, or interfere with one or more of the several steps involved in the aflatoxin metabolism upstream. Recent findings pointed to mitochondrial functionality as one of the potential targets of some aflatoxin inhibitors. Additionally, we have recently reported that the effect of a compound belonging to the class of thiosemicarbazones might be related to the energy generation/carbon flow and redox homeostasis control by the fungal cell. Here, we report our investigation about a putative molecular target of the 3-isopropylbenzaldehyde thiosemicarbazone (mHtcum), using the yeast Saccharomyces cerevisiae as model system, to demonstrate how the compound can actually interfere with the mitochondrial respiratory chain.

Kojic acid applications in cosmetic and pharmaceutical preparations

Skin color disorders can be caused by various factors, such as excessive exposure to sunlight, aging and hormonal imbalance during pregnancy, or taking some medications. Kojic acid (KA) is a natural metabolite produced by fungi that has the ability to inhibit tyrosinase activity in synthesis of melanin. The major applications of KA and its derivatives in medicine are based on their biocompatibility, antimicrobial and antiviral, antitumor, antidiabetic, anticancer, anti-speck, anti-parasitic, and pesticidal and insecticidal properties. In addition, KA and its derivatives are used as anti-oxidant, anti-proliferative, anti-inflammatory, radio protective and skin-lightening agent in skin creams, lotions, soaps, and dental care products. KA has the ability to act as a UV protector, suppressor of hyperpigmentation in human and restrainer of melanin formation, due to its tyrosinase inhibitory activity. Also, KA could be developed as a chemo sensitizer to enhance efficacy of commercial antifungal drugs or fungicides. In general, KA and its derivatives have wide applications in cosmetics and pharmaceutical industries.

Synthesis and Biological Activity of Novel Comenic Acid Derivatives Containing Isoxazole and Isothiazole Moieties

Methyl 5-hydroxy-4-oxo-4 H-pyran-2-carboxylate was synthesized by esterification of methanol with comenic acid under acidic catalysis. The obtained ester was alkylated with 3-(chloromethyl)-5-phenylisoxazole and 4,5-dichloro-3-(chloromethyl)isothiazole to afford corresponding conjugates containing isoxazole and isothiazole moieties which then were transformed into water-soluble Li-salts. During the bioassays of synthesized isoxazole and isothiazole derivatives of comenic acid in mixtures with first-line antitumor drug Temobel (Temozolomid) used in brain tumors chemotherapy, a synergetic effect was observed.

Efficacy of Various Preservatives on Extending Shelf Life of Vacuum-Packaged Raw Pork during 4°C Storage

Uncontrolled bacterial growth and metabolic activities are responsible for the short shelf life of raw pork. Culture-independent analysis by 16S ribosome cDNA could reveal viable bacteria in raw pork. This study investigated microbial growth and volatile organic compounds of raw pork supplemented with various preservatives. Vacuum-packaged raw pork was stored at 4°C, after soaking in solutions of potassium sorbate, ε-poly-l-lysine, kojic acid (KA), or sodium diacetate, individually. Spoilage of raw pork was monitored by determining pH and total volatile basic nitrogen, whereas bacterial growth was determined by culture-dependent and culture-independent analyses. Data indicated that all the preservatives were able to inhibit bacterial growth and extend the shelf life of pork. High-throughput sequencing of 16S ribosome cDNA indicated that Pseudomonas was inhibited under vacuum conditions, whereas facultative anaerobes ( Acinetobacter, Photobacterium, Brochothrix, and Myroides) were the most active genera in the spoiled pork. Photobacterium was further inhibited by each preservative. The inhibition of Acinetobacter, Photobacterium, and Myroides could be responsible for the extended shelf life of vacuum-packaged pork; they were effectively inhibited by KA, which also induced the longest shelf life. Moreover, 19 types of volatile organic compounds were detected. 3-Methylbutanol, 3-methylbutanol acetate, 2-butanone, toluene, benzeneacetaldehyde, dimethyl trisulfide, and acetoin were associated with spoilage. Furthermore, KA is a potential preservative in raw pork; because no phenol was detectable within 35 days, excessive intake of phenol induced by preservatives was avoided.

Biological activity of Diaporthe terebinthifolii extracts against Phyllosticta citricarpa

Citrus black spot disease, caused by the phytopathogen Phyllosticta citricarpa, depreciates the market value of citrus fruits and prevents their exportation to disease-free regions. It may also reduce the productivity of citrus fruit orchards. To identify an alternative to conventional disease control measures, isolates of Diaporthe terebinthifolii, active against P. citricarpa, were selected from an endophytic fungal population of Schinus terebinthifolia leaves. Different culture media were screened to identify the culture medium that afforded the most efficient production of biologically active extracts. A particular fraction (fraction VI) of the extract completely protected orange leaves by inhibiting the germination of P. citricarpa conidia with a minimum inhibitory concentration of 0.003 μg.mL-1. The active constituents in D. terebinthifolii extract fractions were identified by gas chromatography coupled to mass spectrometry as verbanol, phenylethyl alcohol, verbenyl acetate and methyl hexadecanoate. The results obtained strongly suggest the existence of a synergistic effect among the metabolites produced. Thus, these fungal metabolites could be used to control the CBS disease. As the asexual spores of P. citricarpa play an important role in fruit lesion development and disease dispersion, fungal extracts that inhibit the spore germination can be used as an effective alternative for directional disease control.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead

Low-dose exposures to common environmental chemicals that are deemed safe individually may be combining to instigate carcinogenesis, thereby contributing to the incidence of cancer. This risk may be overlooked by current regulatory practices and needs to be vigorously investigated.

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety ‘Mode of Action’ framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.

Chemical compounds from anthropogenic environment and immune evasion mechanisms: potential interactions

An increasing number of studies suggest an important role of host immunity as a barrier to tumor formation and progression. Complex mechanisms and multiple pathways are involved in evading innate and adaptive immune responses, with a broad spectrum of chemicals displaying the potential to adversely influence immunosurveillance. The evaluation of the cumulative effects of low-dose exposures from the occupational and natural environment, especially if multiple chemicals target the same gene(s) or pathway(s), is a challenge. We reviewed common environmental chemicals and discussed their potential effects on immunosurveillance. Our overarching objective was to review related signaling pathways influencing immune surveillance such as the pathways involving PI3K/Akt, chemokines, TGF-β, FAK, IGF-1, HIF-1α, IL-6, IL-1α, CTLA-4 and PD-1/PDL-1 could individually or collectively impact immunosurveillance. A number of chemicals that are common in the anthropogenic environment such as fungicides (maneb, fluoxastrobin and pyroclostrobin), herbicides (atrazine), insecticides (pyridaben and azamethiphos), the components of personal care products (triclosan and bisphenol A) and diethylhexylphthalate with pathways critical to tumor immunosurveillance. At this time, these chemicals are not recognized as human carcinogens; however, it is known that they these chemicalscan simultaneously persist in the environment and appear to have some potential interfere with the host immune response, therefore potentially contributing to promotion interacting with of immune evasion mechanisms, and promoting subsequent tumor growth and progression.