Antifungal activity and action mode of pinocembrin from propolis against Penicillium italicum

Serine Rejuvenated Degenerated Volvariella volvacea by Enhancing ROS Scavenging Ability and Mitochondrial Function

Serine is a functional amino acid that effectively regulates the physiological functions of an organism. This study investigates the effects of adding exogenous serine to a culture medium to explore a feasible method for the rejuvenation of V. volvacea degenerated strains. The tissue isolation subcultured strains T6, T12, and T19 of V. volvacea were used as test strains, and the commercially cultivated strain V844 (T0) was used as a control. The results revealed that the addition of serine had no significant effect on non-degenerated strains T0 and T6, but could effectively restore the production characteristics of degenerated strains T12 and T19. Serine increased the biological efficiency of T12 and even helped the severely degenerated T19 to regrow its fruiting body. Moreover, exogenous serine up-regulated the expression of some antioxidant enzyme genes, improved antioxidase activity, reduced the accumulation of reactive oxygen species (ROS), lowered malondialdehyde (MDA) content, and restored mitochondrial membrane potential (MMP) and mitochondrial morphology. Meanwhile, serine treatment increased lignocellulase and mycelial energy levels. These findings form a theoretical basis and technical support for the rejuvenation of V. volvacea degenerated strains and other edible fungi.

New Insights into the Anti-Oomycete Mechanisms of a Leaf Extract from Glycyrrhiza glabra Against Pseudoperonospora cubensis

Cucurbit downy mildew, caused by Pseudoperonospora cubensis, is responsible for high economic losses worldwide in cucumber production. Synthetic pesticides or copper-based products are still important tools to manage the disease. However, the pathogen has developed resistance against common fungicides rather quickly, and there is a need for alternative plant-protecting agents. Glycyrrhiza glabra leaf extract is known for its antifungal activity and was highly effective in former bioassays and semi-commercial trials against downy mildew of cucumber. To elucidate the active ingredients and the mode of action, licorice leaf extract was here fractionated into five fractions (F1 to F5) with a newly developed and optimized separation process via flash chromatography. The crude extract (P1) and fraction F1 inhibited the zoospore release from sporangia, the zoospore germination, and germ tube development of P. cubensis almost completely on two cucumber cultivars, one tolerant and one susceptible to the pathogen. Infestation rates were reduced between 73 and 96%. F1 contained three previously reported antifungal polyphenols: glabranin, pinocembrin, and licoflavanon. Here, we report an additional new compound, naringenin. Furthermore, F5 is found here to show some protective effects against P. cubensis, based on either direct fungicidal or indirect effects via the host plant. The presented results show that licorice leaf extract can serve as an alternative plant protection agent, able to manage P. cubensis infestation on cucumber cultivars with differing levels of susceptibility by interfering with important early stages in the pathogen development.

Modelling the In Vitro Growth of Phytopathogenic Filamentous Fungi and Oomycetes: The Gompertz Parameters as Robust Indicators of Propolis Antifungal Action

Propolis is a resinous mixture produced by honeybees, mainly from plant exudates. With a rich chemical composition including many phenolic compounds, mostly responsible for its biological properties, namely antimicrobial ones, propolis may be a promising alternative to synthetic pesticides. The study of propolis from the south of Portugal and of its potential against phytopathogenic agents are still very recent and different methodological approaches hinder a comparison of efficacies. In this context, we aimed to test the value of a mathematical model for the multiparametric characterization of propolis' antifungal action on solid medium assays. An ethanol extract (EE) of a propolis sample harvested in 2016 from Alves (A16) was characterized in terms of phenolic composition and antimicrobial potential against five phytopathogenic species. A16.EE (500-2000 µg/mL) inhibited the mycelial growth of all the species, with Phytophthora cinnamomi and Biscogniauxia mediterranea being the most susceptible and Colletotrichum acutatum being the least affected. The Gompertz mathematical model proved to be a suitable tool for quantitatively describing the growth profiles of fungi and oomycetes, and its parameters exhibit a high level of discrimination. Our results reveal that propolis extracts may have potential applications beyond traditional uses, particularly within the agri-food sector, allowing beekeepers to make their businesses more profitable and diversified.

Effect of Potato Glycoside Alkaloids on Energy Metabolism of Fusarium solani

Fusarium solani is one of the primary pathogens causing root rot of wolfberry. The aims of this study were to investigate the inhibitory effect of potato glycoside alkaloids (PGA) on F. solani and its energy metabolism. In this study, the effects of PGA treatment on the growth and development of F. solani were investigated and the changes in the glycolytic pathway (EMP), ATPase activity, mitochondrial complex activity, mitochondrial structure, and energy charge level were analyzed to elucidate the possible antifungal mechanism of PGA on F. solani. The results showed that PGA treatment inhibited the colony growth, biomass, and spore germination of F. solani. PGA treatment reduced the glucose content and Hexokinase (HK) activity of F. solani, but increased the activity of Fructose-6-Phosphate Kinase (PFK) and Pyruvate Kinase (PK) and promoted the accumulation of pyruvic acid. In addition, PGA treatment inhibited the activities of H⁺-ATPase, Ca²⁺-ATPase, and mitochondrial complex IV, increased the mitochondrial inner membrane Ca²⁺ content and mitochondrial membrane permeability transition pore, and decreased the contents of ATP, ADP, and AMP as well as the energy charge. These results indicate that PGA treatment inhibits the growth and development of F. solani, activates the glycolysis pathway, inhibits ATPase activity and mitochondrial complex activity, and destroys the structure and function of mitochondrial membrane, resulting in a lower energy charge level.

Individual and social defenses in Apis mellifera: a playground to fight against synergistic stressor interactions

The honeybee is an important species for the agri-food and pharmaceutical industries through bee products and crop pollination services. However, honeybee health is a major concern, because beekeepers in many countries are experiencing significant colony losses. This phenomenon has been linked to the exposure of bees to multiple stresses in their environment. Indeed, several biotic and abiotic stressors interact with bees in a synergistic or antagonistic way. Synergistic stressors often act through a disruption of their defense systems (immune response or detoxification). Antagonistic interactions are most often caused by interactions between biotic stressors or disruptive activation of bee defenses. Honeybees have developed behavioral defense strategies and produce antimicrobial compounds to prevent exposure to various pathogens and chemicals. Expanding our knowledge about these processes could be used to develop strategies to shield bees from exposure. This review aims to describe current knowledge about the exposure of honeybees to multiple stresses and the defense mechanisms they have developed to protect themselves. The effect of multi-stress exposure is mainly due to a disruption of the immune response, detoxification, or an excessive defense response by the bee itself. In addition, bees have developed defenses against stressors, some behavioral, others involving the production of antimicrobials, or exploiting beneficial external factors.

Current advances on the therapeutic potential of pinocembrin: An updated review

Pinocembrin (5,7-dihydroxyflavone) is a major flavonoid found in many plants, fungi and hive products, mainly honey and propolis. Several in vitro and preclinical studies revealed numerous pharmacological activities of pinocembrin including antioxidant, anti-inflammatory, antimicrobial, neuroprotective, cardioprotective and anticancer activities. Here, we comprehensively review and critically analyze the studies carried out on pinocembrin. We also discuss its potential mechanisms of action, bioavailability, toxicity, and clinical investigations. The wide therapeutic window of pinocembrin makes it a promising drug candidate for many clinical applications. We recommend some future perspectives to improve its pharmacokinetic and pharmacodynamic properties for better delivery that may also lead to new therapeutic advances.

Antifungal Agents in Wood Protection—A Review

The biodegradation of wood and wood products caused by fungi is recognized as one of the most significant problems worldwide. To extend the service life of wood products, wood is treated with preservatives, often with inorganic compounds or synthetic pesticides that have a negative impact on the environment. Therefore, the development of new, environmentally friendly wood preservatives is being carried out in research centers around the world. The search for natural, plant, or animal derivatives as well as obtaining synthetic compounds that will be safe for humans and do not pollute the environment, while at the same time present biological activity is crucial in terms of environmental protection. The review paper presents information in the literature on the substances and chemical compounds of natural origin (plant and animal derivatives) and synthetic compounds with a low environmental impact, showing antifungal properties, used in research on the ecological protection of wood. The review includes literature reports on the potential application of various antifungal agents including plant extracts, alkaloids, essential oils and their components, propolis extract, chitosan, ionic liquids, silicon compounds, and nanoparticles as well as their combinations.

Perspectives for Uses of Propolis in Therapy against Infectious Diseases

Propolis has gained wide popularity over the last decades in several parts of the world. In parallel, the literature about propolis composition and biological properties increased markedly. A great number of papers have demonstrated that propolis from different parts of the world is composed mainly of phenolic substances, frequently flavonoids, derived from plant resins. Propolis has a relevant role in increasing the social immunity of bee hives. Experimental evidence indicates that propolis and its components have activity against bacteria, fungi, and viruses. Mechanisms of action on bacteria, fungi, and viruses are known for several propolis components. Experiments have shown that propolis may act synergistically with antibiotics, antifungals, and antivirus drugs, permitting the administration of lower doses of drugs and higher antimicrobial effects. The current trend of growing resistance of microbial pathogens to the available drugs has encouraged the introduction of propolis in therapy against infectious diseases. Because propolis composition is widely variable, standardized propolis extracts have been produced. Successful clinical trials have included propolis extracts as medicine in dentistry and as an adjuvant in the treatment of patients against COVID-19. Present world health conditions encourage initiatives toward the spread of the niche of propolis, not only as traditional and alternative medicine but also as a relevant protagonist in anti-infectious therapy. Production of propolis and other apiary products is environmentally friendly and may contribute to alleviating the current crisis of the decline of bee populations. Propolis production has had social-economic relevance in Brazil, providing benefits to underprivileged people.

Potential of propolis antifungal activity for clinical applications

The high incidence of skin diseases of microbial origin along with the widespread increase of microbial resistance demand for therapeutic alternatives. Research on natural compounds has been opening new perspectives for the development of new therapies with health positive impacts. Propolis, a resinous mixture produced by honeybees from plant exudates, is widely used as a natural medicine since ancient times, mainly due to its antimicrobial properties. More recently, antioxidant, anti-tumor, anti-inflammatory, hepatoprotective and immunomodulatory activities were also reported for this natural product, highlighting its high potential pharmacological interest. In the present work, an extensive review of the main fungi causing skin diseases as well as the effects of natural compounds, particularly propolis, against such disease-causing microorganisms was organized and compiled in concise handy tables. This information allows to conclude that propolis is a highly effective antimicrobial agent suggesting that it could be used as an alternative skin treatment against pathogenic microorganisms and also as a cosmeceutic component or as a source of bioactive ingredients.

Propolis characterization and antimicrobial activities against Staphylococcus aureus and Candida albicans: A review

Propolis is a plant-based sticky substance that is produced by honeybees. It has been used traditionally by ancient civilizations as a folk medicine, and is known to have many pharmaceutical properties including antioxidant, antibacterial, antifungal, anti-inflammatory, antiviral, and antitumour effects. Worldwide, researchers are still studying the complex composition of propolis to unveil its biological potential, and especially its antimicrobial activity against a variety of multidrug-resistant microorganisms. This review explores scientific reports published during the last decade on the characterization of different types of propolis, and evaluates their antimicrobial activities against Staphylococcus aureus and Candida albicans. Propolis can be divided into different types depending on their chemical composition and physical properties associated with geographic origin and plant sources. Flavonoids, phenols, diterpenes, and aliphatic compounds are the main chemicals that characterize the different types of propolis (Poplar, Brazilian, and Mediterranean), and are responsible for their antimicrobial activity. The extracts of most types of propolis showed greater antibacterial activity against Gram-positive bacteria: particularly on S. aureus, as well as on C. albicans, as compared to Gram-negative pathogens. Propolis acts either by directly interacting with the microbial cells or by stimulating the immune system of the host cells. Some studies have suggested that structural damage to the microorganisms is a possible mechanism by which propolis exhibits its antimicrobial activity. However, the mechanism of action of propolis is still unclear, due to the synergistic interaction of the ingredients of propolis, and this natural substance has multi-target activity in the cell. The broad-spectrum biological potentials of propolis present it as an ideal candidate for the development of new, potent, and cost-effective antimicrobial agents.

Polysaccharide Matrices for the Encapsulation of Tetrahydrocurcumin-Potential Application as Biopesticide against Fusarium graminearum

Cereals are subject to contamination by pathogenic fungi, which damage grains and threaten public health with their mycotoxins. Fusarium graminearum and its mycotoxins, trichothecenes B (TCTBs), are especially targeted in this study. Recently, the increased public and political awareness concerning environmental issues tends to limit the use of traditional fungicides against these pathogens in favor of eco-friendlier alternatives. This study focuses on the development of biofungicides based on the encapsulation of a curcumin derivative, tetrahydrocurcumin (THC), in polysaccharide matrices. Starch octenylsuccinate (OSA-starch) and chitosan have been chosen since they are generally recognized as safe. THC has been successfully trapped into particles obtained through a spray-drying or freeze-drying processes. The particles present different properties, as revealed by visual observations and scanning electron microscopy. They are also different in terms of the amount and the release of encapsulated THC. Although freeze-dried OSA-starch has better trapped THC, it seems less able to protect the phenolic compound than spray-dried particles. Chitosan particles, both spray-dried and lyophilized, have shown promising antifungal properties. The IC₅₀ of THC-loaded spray-dried chitosan particles is as low as 0.6 ± 0.3 g/L. These particles have also significantly decreased the accumulation of TCTBs by 39%.

Antiviral, Antibacterial, Antifungal, and Antiparasitic Properties of Propolis: A Review

Propolis is a complex phytocompound made from resinous and balsamic material harvested by bees from flowers, branches, pollen, and tree exudates. Humans have used propolis therapeutically for centuries. The aim of this article is to provide comprehensive review of the antiviral, antibacterial, antifungal, and antiparasitic properties of propolis. The mechanisms of action of propolis are discussed. There are two distinct impacts with regards to antimicrobial and anti-parasitic properties of propolis, on the pathogens and on the host. With regards to the pathogens, propolis acts by disrupting the ability of the pathogens to invade the host cells by forming a physical barrier and inhibiting enzymes and proteins needed for invasion into the host cells. Propolis also inhibits the replication process of the pathogens. Moreover, propolis inhibits the metabolic processes of the pathogens by disrupting cellular organelles and components responsible for energy production. With regard to the host, propolis functions as an immunomodulator. It upregulates the innate immunity and modulates the inflammatory signaling pathways. Propolis also helps maintain the host's cellular antioxidant status. More importantly, a small number of human clinical trials have demonstrated the efficacy and the safety of propolis as an adjuvant therapy for pathogenic infections.

Mitochondrial damage produced by phytotoxic chromenone and chromanone derivatives from endophytic fungus Daldinia eschscholtzii strain GsE13

Bioassay-guided fractionation of the organic extracts of the endophyte Daldinia eschscholtzii strain GsE13 led to the isolation of several phytotoxic compounds, including two chromenone and two chromanone derivatives: 5-hydroxy-8-methoxy-2-methyl-4H-chromen-4-one, 1; 5-hydroxy-2-methyl-4H-chromen-4-one, 2; 5-methoxy-2-methyl-chroman-4-one, 3; and 5-methoxy-2-methyl-chroman-4-ol, 4; as well as other aromatic compounds: 4,8-dihydroxy-1-tetralone, 5; 1,8-dimethoxynaphthalene, 6; and 4,9-dihydroxy-1,2,11,12-tetrahydroperyl-ene-3,10-quinone, 7. Compounds 1, 4, and 7 were isolated for the first time from D. eschscholtzii. The phytotoxicity of all the compounds was determined on germination, root growth, and oxygen uptake in seedlings of a monocotyledonous (Panicum miliaceum) and three dicotyledonous plants (Medicago sativa, Trifolium pratense, and Amaranthus hypochondriacus). In general, root growth was the most affected process in all four weeds, and chromenones 1 and 2 were the most phytotoxic compounds. Phytotoxins 1-4 inhibited basal oxygen consumption rate in isolated mitochondria from M. sativa seedlings and also caused serious damage to their membrane potential (ΔΨm) in percentages greater than 50% at concentrations lower than 2 mM. Based on these results, compounds 1-4 of endophytic origin could be promising for the development of new herbicides potentially useful in agriculture or for the synthesis of promising new molecules. KEY POINTS: • Endophytic fungus Daldinia eschscholtzii produces phytotoxic compounds. • Phytotoxins inhibit basal oxygen consumption rate in isolated M. sativa mitochondria. • Phytotoxins altered the mitochondrial membrane potential.

Potency of plant extracts against Penicillium species isolated from different seeds and fruits in Saudi Arabia

Antifungal activity of extracts of cinnamon (Cinnamomum zeylanicum), Cloves (Syzygium aromaticum), ginger (Zingiber officinale) and turmeric (Curcuma longa) were evaluated in vitro against 17 Penicillium spp. Seed disease and rotten fruit caused by these species cause considerable loss of quality for different agricultural products. Isolates of Penicillium spp. were screened for production of patulin an important serious mycotoxin. About 70.59% of Penicillium spp. produced this toxin in concentrations ranging from 4 to 31 ppb. The response of Penicillium spp.

to plant extracts differed according to the plant extract and concentration. Cinnamon extract showed the greatest effect on P. asperosporum, P. aurintogriseum and P. brevicompactum, and cloves extract produced the greatest effect on P. chermesinum and P. duclauxii. Turmeric extract had less effect on P. duclauxii. Cloves extract was the most effective in reducing the growth of Penicillium spp. On the other hand, ginger extract with all concentrations used had less effect against most Penicillium spp in the laboratory. Plant extracts are promising as natural sources of environmentally friendly compounds in laboratory studies.

Screening of Wood/Forest and Vine By-Products as Sources of New Drugs for Sustainable Strategies to Control Fusarium graminearum and the Production of Mycotoxins

Fusarium graminearum is a fungal pathogen that can colonize small-grain cereals and maize and secrete type B trichothecene (TCTB) mycotoxins. The development of environmental-friendly strategies guaranteeing the safety of food and feed is a key challenge facing agriculture today. One of these strategies lies on the promising capacity of products issued from natural sources to counteract crop pests. In this work, the in vitro efficiency of sixteen extracts obtained from eight natural sources using subcritical water extraction at two temperatures was assessed against fungal growth and TCTB production by F. graminearum. Maritime pine sawdust extract was shown to be extremely efficient, leading to a significant inhibition of up to 89% of the fungal growth and up to 65% reduction of the mycotoxin production by F. graminearum. Liquid chromatography/mass spectrometry analysis of this active extract revealed the presence of three families of phenolics with a predominance of methylated compounds and suggested that the abundance of methylated structures, and therefore of hydrophobic compounds, could be a primary factor underpinning the activity of the maritime pine sawdust extract. Altogether, our data support that wood/forest by-products could be promising sources of bioactive compounds for controlling F. graminearum and its production of mycotoxins.

Alternative Management Approaches of Citrus Diseases Caused by Penicillium digitatum (Green Mold) and Penicillium italicum (Blue Mold)

Green mold (Penicillium digitatum) and blue mold (Penicillium italicum) are among the most economically impactful post-harvest diseases of citrus fruit worldwide. Post-harvest citrus diseases are largely controlled with synthetic fungicides such as pyrimethanil, imazalil, fludioxonil, and thiabendazole. Due to their toxic effects, prolonged and excessive application of these fungicides is gradually restricted in favor of safe and more eco-friendly alternatives. This review comprehensively describes alternative methods for the control of P. digitatum and P. italicum: (a) antagonistic micro-organisms, (b) plant extracts and essential oils, (c) biofungicides, (d) chitosan and chitosan-based citrus coatings, (e) heat treatments, (f) ionizing and non-ionizing irradiations, (g) food additives, and (h) synthetic elicitors. Integrating multiple approaches such as the application of biocontrol agents with food additives or heat treatments have overcome some drawbacks to single treatments. In addition, integrating treatment approaches could produce an additive or synergistic effect on controlling both molds for a satisfactory level of disease reduction in post-harvest citrus. Further research is warranted on plant resistance and fruit-pathogen interactions to develop safer strategies for the sustainable control of P. digitatum and P. italicum in citrus.

Penicillium italicum: An Underexplored Postharvest Pathogen

In the agricultural sector, citrus is one of the most important fruit genus in the world. In this scenario, Brazil is the largest producer of oranges; 34% of the global production, and exporter of concentrated orange juice; 76% of the juice consumed in the planet, summing up US$ 6.5 billion to Brazilian GDP. However, the orange production has been considerable decreasing due to unfavorable weather conditions in recent years and the increasing number of pathogen infections. One of the main citrus post-harvest phytopathogen is Penicillium italicum, responsible for the blue mold disease, which is currently controlled by pesticides, such as Imazalil, Pyrimethanil, Fludioxonil, and Tiabendazole, which are toxic chemicals harmful to the environment and also to human health. In addition, P. italicum has developed considerable resistance to these chemicals as a result of widespread applications. To address this growing problem, the search for new control methods of citrus post-harvest phytopathogens is being extensively explored, resulting in promising new approaches such as biocontrol methods as “killer” yeasts, application of essential oils, and antimicrobial volatile substances. The alternative methodologies to control P. italicum are reviewed here, as well as the fungal virulence factors and infection strategies. Therefore, this review will focus on a general overview of recent research carried out regarding the phytopathological interaction of P. italicum and its citrus host.

Boesenbergia rotunda extract inhibits Candida albicans biofilm formation by pinostrobin and pinocembrin

ETHNOPHARMACOLOGICAL RELEVANCE

Boesenbergia rotunda (L.) Mansf. (Zingiberaceae) is an indigenous plant of Southeast Asia. Based on ethnopharmacological use, the rhizome is recommended in the treatment of stomachache, leukoplakia, abscesses, and leukorrhea in Thailand primary health care system. Candida albicans often causes leukorrhea, and infection of many mucosal sites. Its infection leads to serious illness.

AIM OF THE STUDY

This study aimed to investigate the effects of the ethanolic extract of the B. rotunda rhizome on C. albicans ATCC10231 in the stages of planktonic and biofilm formation and to explore the underlying mechanisms.

MATERIALS AND METHODS

The chemical composition of the extract was determined using ultra-performance liquid chromatography (UPLC). The planktonic growth of C. albicans was evaluated by the microdilution method, following EUCAST guidelines. For each stage of biofilm formation, the biofilm was assessed by the MTT assay. The biofilm structure was examined under a light microscope. The degree of cell surface hydrophobicity was measured. The mRNA levels of ALS1, ALS3, and ACT1 were determined by RT-qPCR.

RESULTS

The extract of B. rotunda consisted of 25% (w/w) pinostrobin and 12% (w/w) pinocembrin. All stages of C. albicans biofilm formation were significantly inhibited by the extract, whereas the planktonic growth did not change. Biofilm development greatly decreased due to the extract in a concentration-dependent manner, with an IC₅₀ value of 17.7 μg/mL. Pinostrobin and pinocembrin demonstrated inhibitory effects during this stage. These results were in accordance with the microscopic evaluation. The filamentous form decreased with pinocembrin rather than pinostrobin. Moreover, the cell surface hydrophobicity was significantly decreased by 6.25 and 12.5 μg/mL of the extract and 100 μM of pinocembrin. The ALS3 mRNA level was noticeably decreased by 12.5 μg/mL of the extract, 100 μM of pinostrobin, and 100 μM of pinocembrin. The ACT1 mRNA level decreased significantly with pinocembrin. However, the ALS1 mRNA level was not altered following all treatments.

CONCLUSION

The ethanolic extract of B. rotunda could inhibit biofilm formation of C. albicans, especially during the biofilm development stage, by means of reducing the cell surface hydrophobicity and suppressing the ALS3 mRNA expression. Pinocembrin had a stronger effect on ALS3 mRNA expression than pinostrobin. Only pinocembrin significantly decreased the ACT1 mRNA level.

Utilization of straw-based phenolic acids as a biofugicide for a green agricultural production

Phenolic compounds inhibit phytopathogenic fungal infections effectively. In this study, the antifungal effects of rice straw-derived phenolic acids (PAs) against Fusarium oxysporum were investigated. PAs can inhibit hyphal growth and spore germination, and p-coumaric acid (CA) is the main antifungal substance in PAs. PAs could induce the formation of hydrogen peroxide and increase the relative conductivity and extracellular K⁺ concentration. Observations using Scanning Electron Microscopy, Laser Scanning Confocal Microscopy and Transmission Electron Microscopy revealed that PAs could damage membrane permeability, which caused cytoplasm leakage. This phenomenon was verified by conductivity and the release of extracellular K⁺. The chlorophyll fluorescence maps of tomato leaves suggested that F. oxysporum damaged the tomato' photosynthetic system and that PAs reduced the area infected, thereby alleviating the damage. Moreover, PAs could decrease the disease incidence of tomato fruit. The results confirmed the feasibility of using PAs as a biofungicide and provide a way to increase the value of rice straw.

Antifungal and antioomycete activities and modes of action of isobenzofuranones isolated from the endophytic fungus Hypoxylon anthochroum strain Gseg1

Hypoxylon species are distributed worldwide and have been isolated from different habitats. The endophyte Hypoxylon anthochroum strain Gseg1 was isolated from healthy leaves of Gliricidia sepium. A chemical study of the culture medium and mycelium organic extracts of the endophytic fungus H. anthochroum Gseg1 led to the isolation of three known isobenzofuranones, 7-hydroxy-4,6-dimethyl-3H-isobenzofuran-1-one, 1, 7-methoxy-4,6-dimethyl-3H-isobenzofuran-1-one, 2, 6-formyl-4-methyl-7-methoxy-3H-isobenzofuran-1-one, 3, and one compound was isolated for the first time as a natural product, 7-methoxy-4-methyl-3H-isobenzofuran-1-one, 4. In addition, the chemical synthesis of 1 and 2, and a derivative, 7-methoxy-6-methyl-3H-isobenzofuran-1-one, 5, was performed. The isobenzofuranones showed antifungal and antioomycete activities. Compounds 1-5 inhibited the growth of Fusarium oxysporum, Alternaria alternata, Pythium aphanidermatum, and Phytophthora capsici, in addition, 1, 2 and 5 interrupted the respiration and caused electrolyte leakage due to cell membrane damage. Compound 2 was the most active, inhibiting the growth of the four microorganisms, affecting the respiration and increasing the relative conductivity due to electrolyte leakage. Compounds 1-4 also induce morphological changes in the plant pathogens' mycelia and hyphae. These compounds could be useful for the control of plant pathogenic fungi and oomycetes of agricultural relevance.

Antifungal activity and toxicity studies of flavanones isolated from Tessaria dodoneifolia aerial parts

Tessaria dodoneifolia [Asteraceae] is traditionally employed in Northwestern Argentina for fungal infections treatment. We report the antifungal activity guided isolation and identification of substances from aerial parts of this species, both individually and in combination with fluconazole (FLU), against Candida albicans strains. Two antifungal flavanones were identified as naringenin (NAR) and pinocembrin (PIN). These compounds could individually inhibit the growth of C. albicans strains. Combinations of NAR and PIN with FLU were synergistic against the FLU resistant and sensitive C. albicans strains. Genotoxic and cytotoxic evaluations were also performed. NAR, PIN and their combinations with FLU did not have a genotoxic effect on Bacillus subtilis rec strains. Finally, these compounds did not show cytotoxicity at concentrations below 80 μg/mL.

Effect of the Solvent on Propolis Phenolic Profile and its Antifungal, Antioxidant, and In Vitro Cytoprotective Activity in Human Erythrocytes Under Oxidative Stress

Propolis is a natural bee product with various beneficial biological effects. The health-promoting properties of propolis depend on its chemical composition, particularly the presence of phenolic compounds. The aim of this study was to evaluate the relationship between extraction solvent (acetone 100%, ethanol 70% and 96%) and the antifungal, antioxidant, and cytoprotective activity of the extracts obtained from propolis. Concentrations of flavonoids and phenolic acids in the propolis extracts were determined using ultrahigh-performance liquid chromatography. The antioxidant potential of different extracts was assessed on the basis of 2,2-diphenyl-1-picrylhydrazyl (DPPH·) free-radical-scavenging activity, Fe³⁺-reducing power, and ferrous ion (Fe²⁺)-chelating activity assays. The ability of the extracts to protect human red blood cell membranes against free-radical-induced damage and their antifungal activity was also determined. The results showed that the concentration of flavonoids in the propolis extracts was dependent on the solvent used in the extraction process and pinocembrin, chrysin, galangin, and coumaric acid were the most abundant phenols. All extracts exhibited high antioxidant potential and significantly protected human erythrocytes against oxidative damage. On the other hand, the antifungal activity of the propolis extracts depended on the solvent used in extraction and the fungal strains tested. It needs to be stressed that, to the best of our knowledge, there is no study relating the effect of solvent used for extraction of Polish propolis to its phenolic profile, and its antifungal, antioxidant, and cytoprotective activity.

Physiological and iTRAQ-based proteomic analyses reveal the mechanism of pinocembrin against Penicillium italicum through targeting mitochondria

The physiological and iTRAQ-based proteomic analyses were used to reveal the inhibitory roles of pinocembrin on mitochondria of P. italicum and its cell death mechanism. The results show that pinocembrin damages both mitochondrial structure and function. 167 and 807 differentially expressed proteins (DEPs) were detected in P. italicum mycelia after treatment with pinocembrin for 8 h and 24 h respectively, and the DEPs were significantly enriched in the oxidative phosphorylation (OXPHOS) pathway, especially for mitochondrial respiratory chain (MRC) complexes I and V. Furthermore, the expression levels of proteins related to programmed cell death (PCD) were significantly up-regulated in mycelia with Pinocembrin incubation for 24 h. Combined with the results of physio-chemical analysis, the data revealed that pinocembrin targeted MRC complexes I and V, to induce ATP depletion, enhance ROS accumulation, stimulate mitochondrial permeability transition pore (MPTP) opening, accelerate the loss of mitochondrial membrane potential (MMP) and promote cytochrome c release from mitochondria to the cytoplasm, which, as a result, effectively triggered three classical types of PCD pathways in mycelia of P. italicum.

A flavonone pinocembroside inhibits Penicillium italicum growth and blue mold development in 'Newhall' navel oranges by targeting membrane damage mechanism

Blue mold caused by Penicillium italicum is an important postharvest disease of citrus fruit. The antifungal activity of a flavonone pinocembroside compound obtained from the fruit of Ficus hirta Vahl., was evaluated against P. italicum. Pinocembroside showed antifungal activity against in vitro mycelial growth of P. italicum, with the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of 200 and 800 mg/L, respectively. The blue mold development on 'Newhall' navel oranges was inhibited by pinocembroside in a dose-dependent manner. Moreover, pinocembroside might exert its antifungal activity via membrane-targeted mechanism with increasing membrane permeability, reduction of antioxidant enzyme activity and acceleration of lipid peroxidation in the pathogen. This pioneering study suggested that pinocembroside suppressed postharvest blue mold by direct inhibition of P. italicum mycelial growth via membrane-targeting mechanism, thus providing a novel mode of action against traditional fungicides for controlling blue mold of citrus fruit.

Pinocembrin-7-Glucoside (P7G) Reduced Postharvest Blue Mold of Navel Orange by Suppressing Penicillium italicum Growth

The current study aimed to examine the in vitro and in vivo antifungal potential of pinocembrin-7-glucoside (P7G). P7G is an antifungal flavanone glycoside isolated from Ficus hirta Vahl. fruit against Penicillium italicum, a causative pathogen of blue mold disease in citrus fruit, and this study elucidates its possible action mechanism. P7G had a prominent mycelial growth inhibitory activity against P. italicum, with an observed half maximal effective concentration, minimum inhibitory concentration and minimum fungicidal concentration of 0.08, 0.2, and 0.8 g/L, respectively. The data from the in vivo test show that P7G significantly reduced blue mold symptoms and disease development of P. italicum in artificially inoculated "Newhall" navel orange. Compared to the control, increases in the cell membrane permeability of P. italicum supernatant and decreases in the intracellular constituent (e.g., soluble protein, reducing sugar, and total lipid) contents of P. italicum mycelia were identified, supporting scanning electron microscopy and transmission electron microscopy observations. Furthermore, a marked decline in both chitin and glucanase contents of P. italicum mycelia treated with P7G was induced by increasing its related degrading enzyme activities, suggesting that the cell wall structure was destroyed. The current study indicated that P7G may be a novel alternative for reducing blue mold by suppressing mycelial growth of P. italicum via a cell membrane/wall-targeting mechanism.

Potential Application of Propolis Extracts to Control the Growth of Stemphylium vesicarium in “Rocha” Pear

Stemphylium vesicarium (Wallr.) E. G. Simmons is the pathogen responsible of brown spot disease in pear and has become one of the main concerns for European pear producers. In Portugal, S. vesicarium is responsible for significant yield reduction and economic losses in “Rocha” pear (Pyrus communis L. cv Rocha) production. Considering the antimicrobial potential of propolis, the high incidence of brown spot in pears and the emergence of fungicides resistance in S. vesicarium, this study aimed to evaluate the potential of Portuguese propolis as an alternative strategy to control brown spot disease in “Rocha” pear. In vitro assays showed that propolis extracts were able to inhibit up to 90% the S. vesicarium mycelial growth. In vivo assays in artificially wounded and inoculated “Rocha” pears showed that, compared to the control, the disease incidence decreased up to 25% and the lesions diameter up to 57%, in fruits treated with propolis. Moreover, propolis seems to be more efficient in reducing the disease incidence when applied after pathogen inoculation (curative assay) than when applied before pathogen inoculation (prophylactic assay). Thus, the results suggest that propolis extracts have potential to be applied as part of an integrated approach for the control of brown spot of pear.

Bee Products in Dermatology and Skin Care

Honey, propolis, bee pollen, bee bread, royal jelly, beeswax and bee venom are natural products which have been used in medicine since ancient times. Nowadays, studies indicate that natural bee products can be used for skin treatment and care. Biological properties of these products are related to flavonoids they contain like: chrysin, apigenin, kaempferol, quercetin, galangin, pinocembrin or naringenin. Several pharmacological activities of phenolic acids and flavonoids, and also 10-hydroxy-trans-2-decenoic acid, which is present in royal jelly, have been reported. Royal jelly has multitude of pharmacological activities: antibiotic, antiinflammatory, antiallergenic, tonic and antiaging. Honey, propolis and pollen are used to heal burn wounds, and they possess numerous functional properties such as: antibacterial, anti-inflammatory, antioxidant, disinfectant, antifungal and antiviral. Beeswax is used for production of cosmetics and ointments in pharmacy. Due to a large number of biological activities, bee products could be considered as important ingredients in medicines and cosmetics applied to skin.

Chemical Compositions of Propolis from China and the United States and their Antimicrobial Activities Against Penicillium notatum

The chemical compositions of ethanol extracts of propolis from China (EEP-C) and the United States (EEP-A) and their antifungal activity against Penicillium notatum were determined. The result showed that a total of 49 compounds were detected by UPLC-Q-TOF-MS, 30 of which were present in samples from two regions. The major compounds of EEP-C and EEP-A were similar, including pinocembrin, pinobanksin-3-O-acetate, galanin, chrysin, pinobanksin, and pinobanksin-methyl ether, and both of them showed antifungal activity against P. notatum with same minimum inhibitory concentration (MIC) value of 0.8 mg·mL-1. In the presence of propolis, the mycelial growth was inhibited, the hyphae became shriveled and wrinkled, the extracellular conductivities were increased, and the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) were decreased. In addition, iTRAQ-based quantitative proteomic analysis of P. notatum in response to propolis revealed that a total of 341 proteins were differentially expressed, of which 88 (25.8%) were upregulated and 253 (74.2%) were downregulated. Meanwhile, the differentially expressed proteins (DEPs) involved in energy production and conversion, carbohydrate transport and metabolism, and the sterol biosynthetic pathway were identified. This study revealed that propolis could affect respiration, interfere with energy metabolism, and influence steroid biosynthesis to inhibit the growth of P. notatum.

Biological Control of Citrus Postharvest Phytopathogens

Citrus are vulnerable to the postharvest decay caused by Penicillium digitatum, Penicillium italicum, and Geotrichum citri-aurantii, which are responsible for the green mold, blue mold, and sour rot post-harvest disease, respectively. The widespread economic losses in citriculture caused by these phytopathogens are minimized with the use of synthetic fungicides such as imazalil, thiabendazole, pyrimethanil, and fludioxonil, which are mainly employed as control agents and may have harmful effects on human health and environment. To date, numerous non-chemical postharvest treatments have been investigated for the control of these pathogens. Several studies demonstrated that biological control using microbial antagonists and natural products can be effective in controlling postharvest diseases in citrus, as well as the most used commercial fungicides. Therefore, microbial agents represent a considerably safer and low toxicity alternative to synthetic fungicides. In the present review, these biological control strategies as alternative to the chemical fungicides are summarized here and new challenges regarding the development of shelf-stable formulated biocontrol products are also discussed.

Pinocembrin Protects Against Dextran Sulfate Sodium-Induced Rats Colitis by Ameliorating Inflammation, Improving Barrier Function and Modulating Gut Microbiota

Pinocembrin (PIN) is a natural flavonoid widely found in bee propolis with potent gastrointestinal protective effects. In consequence, PIN has great potential in preventing inflammatory bowel diseases (IBDs) while scant information is available. In this study, a dextran sulfate sodium (DSS)-induced rats ulcerative colitis model (3.5% DSS in drinking water for 7 days) was applied to explore the protective effects of PIN on macroscopic colitis symptoms, inflammation, intestinal epithelial barrier function, and gut microbiota homeostasis. While DSS-treated rats showed severe colitis clinical symptoms and histological changes (colonic pathological damages and intestinal goblet cells loss), pre-administration of PIN (5 and 10 mg/kg, p.o.) for a week alleviated these symptoms. Pre-administration of PIN also suppressed the pro-inflammatory gene expressions and improved tight junction functions of colonic epithelial cells. Additionally, PIN administration reversed DSS-induced short chain fatty acid loss, and improved the gut microbial diversity assessed by 16S rRNA phylogenetic sequencing. Overall, our results suggest a wide spectrum of protective effects of PIN in preventing IBDs.

The new buzz: Investigating the antimicrobial interactions between bioactive compounds found in South African propolis

ETHNOPHARMACOLOGICAL RELEVANCE

Propolis, a resinous substance produced by the Apis mellifera bee, contains a number of flavonoids sourced from plants found in the surrounding region. Whilst bees use this substance to seal off and protect the beehive, humans have used propolis therapeutically for centuries, making use of its antibacterial, antiseptic, antipyretic and wound healing properties, among others. South African propolis is rich in the flavonoids pinocembrin, galangin, and chrysin and very little previous research has been conducted on the antimicrobial effects of these compounds.

AIM OF THE STUDY

To obtain an understanding of the antimicrobial activity of the compounds pinocembrin, galangin, and chrysin, both independently and in combination.

MATERIALS AND METHODS

The compounds pinocembrin, galangin and chrysin were investigated for interactive antimicrobial activity by determining the minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), anti-quorum sensing activity, biofilm studies, and toxicity studies (brine shrimp lethality assay).

RESULTS

Minimum inhibitory concentration results demonstrated that combinations of compounds showed better inhibitory activity than single compounds. When the flavonoids were tested in combination using the MIC assay, synergy was noted for 22% of the 1:1 ratio combinations and for 66% of the triple 1:1:1 ratio combinations. Similarly, MBC results showed bactericidal activity from selected combinations, while the compounds on their own demonstrated no cidal activity. Quorum sensing studies showed that compound combinations are more effective at inhibiting bacterial communication than the individual compounds. Biofilm assays showed that the highest percentage inhibition was observed for the triple combination against E. coli at 24 h. Finally, brine shrimp lethality studies revealed that combinations of the three compounds had reduced cytotoxicity when compared to the individual compounds.

CONCLUSION

The results obtained in this study demonstrate that the compounds found in South African propolis work synergistically to achieve an optimal antimicrobial effect, whilst simultaneously minimizing cytotoxicity.

Inhibitory Effect of 7-Demethoxytylophorine on Penicillium italicum and its Possible Mechanism

7-demethoxytylophorine (DEM) is a phenanthroindolizidine alkaloid, which is reported to be effective in inhibiting leucocytes and regulation of human immunity. However, few studies reported the inhibitory effect of DEM against plant-pathogenic fungi, particularly postharvest pathogen Penicillium italicum (P. italicum). Current studies have investigated the antifungal activity of DEM through membrane damage and energy deficit in P. italicum. The results showed that the DEM potentially inhibits the growth of P. italicum in a dose-dependent manner. In vitro (mycelial growth and spore germination) tests showed great minimal inhibitory concentration (MIC) (1.56 µg mL-1) and minimum fugicide concentration (MFC) (6.25 µg mL-1). Microscopic analyses showed that mycelial morphology of P. italicum was severely damaged following DEM treatment. Moreover, relative electrical conductivity and lysis ability assays showed that DEM treatment aids in destroying the integrity of plasma membranes that deplete reducing sugars and soluble proteins. The activity of malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) demonstrated that DEM led to the disruption of TCA cycle in P. italicum mycelia. The results of this study led us to conclude that, DEM could be used as a natural antifungal agent for controlling postharvest blue mold disease of citrus fruits caused by P. italicum.

Building a minimal and generalizable model of transcription factor-based biosensors: Showcasing flavonoids

Progress in synthetic biology tools has transformed the way we engineer living cells. Applications of circuit design have reached a new level, offering solutions for metabolic engineering challenges that include developing screening approaches for libraries of pathway variants. The use of transcription-factor-based biosensors for screening has shown promising results, but the quantitative relationship between the sensors and the sensed molecules still needs more rational understanding. Herein, we have successfully developed a novel biosensor to detect pinocembrin based on a transcriptional regulator. The FdeR transcription factor (TF), known to respond to naringenin, was combined with a fluorescent reporter protein. By varying the copy number of its plasmid and the concentration of the biosensor TF through a combinatorial library, different responses have been recorded and modeled. The fitted model provides a tool to understand the impact of these parameters on the biosensor behavior in terms of dose-response and time curves and offers guidelines to build constructs oriented to increased sensitivity and or ability of linear detection at higher titers. Our model, the first to explicitly take into account the impact of plasmid copy number on biosensor sensitivity using Hill-based formalism, is able to explain uncharacterized systems without extensive knowledge of the properties of the TF. Moreover, it can be used to model the response of the biosensor to different compounds (here naringenin and pinocembrin) with minimal parameter refitting.

Biological activities of Agave by-products and their possible applications in food and pharmaceuticals

Agave leaves are considered a by-product of alcoholic beverage production (tequila, mezcal and bacanora) because they are discarded during the production process, despite accounting for approximately 50% of the total plant weight. These by-products constitute a potential source of Agave extracts rich in bioactive compounds, such as saponins, phenolic compounds and terpenes, and possess different biological effects, as demonstrated by in vitro and in vivo tests (e.g. antimicrobial, antifungal, antioxidant, anti-inflammatory, antihypertensive, immunomodulatory, antiparasitic and anticancer activity). Despite their positive results in biological assays, Agave extracts have not been widely evaluated in food systems and pharmaceutical areas, and these fields represent a potential route to improve the usage of Agave plants as food additives and agents for treating medical diseases. © 2017 Society of Chemical Industry.

Antifungal Activity and Action Mode of Cuminic Acid from the Seeds of Cuminum cyminum L. against Fusarium oxysporum f. sp. Niveum (FON) Causing Fusarium Wilt on Watermelon

In order to develop a novel biofungicide, the antifungal activity and action mode of cuminic acid from the seed of Cuminum cyminum L. against Fusarium oxysporum f. sp. niveum (FON) on watermelon was determined systematically. In this study, the median effective concentration (EC50) value for cuminic acid in inhibiting mycelial growth of FON was 22.53 μg/mL. After treatment with cuminic acid, the mycelial morphology was seriously influenced; cell membrane permeability and glycerol content were increased markedly, but pigment and mycotoxin (mainly fusaric acid) were significantly decreased. Synthesis genes of bikaverin (Bike1, Bike2 and Bike3) and fusaric acid (FUB1, FUB2, FUB3 and FUB4) both were downregulated compared with the control, as confirmed by quantitative RT-PCR. In greenhouse experiments, cuminic acid at all concentrations displayed significant bioactivities against FON. Importantly, significant enhancement of activities of SOD, POD, CAT and decrease of MDA content were observed after in vivo cuminic acid treatment on watermelon leaves. These indicated that cuminic acid not only showed high antifungal activity, but also could enhance the self-defense system of the host plant. Above all, cuminic acid showed the potential as a biofungicide to control FON.

Pinus pinaster Knot: A Source of Polyphenols against Plasmopara viticola

Pine knot extract from Pinus pinaster byproducts was characterized by UHPLC-DAD-MS and NMR. Fourteen polyphenols divided into four classes were identified as follows: lignans (nortrachelogenin, pinoresinol, matairesinol, isolariciresinol, secoisolariciresinol), flavonoids (pinocembrin, pinobanksin, dihydrokaempferol, taxifolin), stilbenes (pinosylvin, pinosylvin monomethyl ether, pterostilbene), and phenolic acids (caffeic acid, ferulic acid). The antifungal potential of pine knot extract, as well as the main compounds, was tested in vitro against Plasmopara viticola. The ethanolic extract showed a strong antimildew activity. In addition, pinosylvins and pinocembrin demonstrated significant inhibition of zoospore mobility and mildew development. These findings strongly suggest that pine knot is a potential biomass that could be used as a natural antifungal product.

Volatile organic compounds from endophytic fungi as innovative postharvest control of Fusarium oxysporum in cherry tomato fruits

To assess their potential as biopesticides, the effect on the growth of phytopathogen Fusarium oxysporum of six volatile organic compounds from endophytic fungi was studied in vivo and in vitro; compounds were used both as a mixture and individually. In vivo studies were performed inoculating the pathogen into cherry tomatoes, while the in vitro antifungal effect was studied using agar dilution and gas phase methods. Also, the morphology of the hyphae exposed to these compounds was analyzed. Moreover, the possible mechanism of action of these compounds was determined by studying the respiration and cell membrane permeability. Results show that the compounds have a significant concentration-dependent antifungal effect individually and act in a synergic manner. Additionally, changes in cell membrane permeability, damage to the hyphal morphology, and an inhibitory effect on the respiration were observed. The mixture of the six compounds may be used for postharvest control of F. oxysporum in tomatoes.

Chemical Constituents and Antifungal Activity of Ficus hirta Vahl. Fruits

Phytochemical investigation of Ficus hirta Vahl. (Moraceae) fruits led to isolate two carboline alkaloids (1 and 2), five sesquiterpenoids/norsesquiterpenoids (3-7), three flavonoids (8-10), and one phenylpropane-1,2-diol (11). Their structures were elucidated by the analysis of their 1D and 2D NMR, and HR-ESI-MS data. All of the isolates were isolated from this species for the first time, while compounds 2, 4-6, and 8-11 were firstly reported from the genus Ficus. Antifungal assay revealed that compound 8 (namely pinocembrin-7-O-β-d-glucoside), a major flavonoid compound present in the ethanol extract of F. hirta fruits, showed good antifungal activity against Penicillium italicum, the phytopathogen of citrus blue mold caused the majority rotten of citrus fruits.

Chemical and cytotoxic analyses of brown Brazilian propolis (Apis mellifera) and its in vitro activity against itraconazole-resistant Sporothrix brasiliensis

This study aimed to evaluate the chemical composition and cytotoxic activity of brown Brazilian propolis and its in vitro activity against itraconazole-resistant Sporothrix brasiliensis from animal sporotrichosis. Propolis was acquired commercially and prepared as a hydroalcoholic extract. Chemical analysis was evaluated by liquid chromatography coupled to mass spectrometry of ultra-efficiency. The cell viability was evaluated by MTT test in MDBK cells of 50 to 0.09 μg/mL. For antifungal tests, twenty isolates of Sporothrix brasiliensis from dogs (n = 11) and cats (n = 9) with sporotrichosis were tested to itraconazole (16-0.0313 μg/mL) and to propolis (3.125-0.09 mg/mL) by broth microdilution technique (CLSI M38-A2), adapted to natural products. The results were expressed in minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC). Itraconazole showed activity between MIC values of 0.25 to greater than 16 μg/mL, and 88.9% (08/09) and 72.7% (08/11) of S. brasiliensis from cats and dogs, respectively, were considered itraconazole-resistant. All Sporothrix brasiliensis were sensitive to brown propolis between MIC values of 0.19-1.56 mg/mL, including the itraconazole-resistant isolates, whereas the MFC values of propolis were from 0.78 to greater than 3.125 mg/mL. Propolis maintained a medium to high cell viability between concentration of 0.78 to 0.09 μg/mL, and p-coumaric acid was the major compound. Brown Brazilian propolis is a promising antifungal candidate against sporotrichosis and more studies need to be undertaken to evaluate its safe use to understand its efficacy.

The structure-antifungal activity relationship of 5,7-dihydroxyflavonoids against Penicillium italicum

To evaluate the structure-activity relationship of 5,7-dihydroxyflavonoids against P. italicum, we tested the antifungal activity of 23 selected 5,7-dihydroxyflavonoids against spore germination of P. italicum, and the effects of hydroxyl group, hydrogenation, methylation and glycosylation on the antifungal activity are explored. C-4'-OH and C-3-OH are active groups for the 5,7-dihydroxyflavonoids against P. italicum. We find that hydrogenation of the C2/C3 bond decreases the antifungal activity of 5,7-dihydroxyflavonoids. Antifungal activity of 5,7-dihydroxyflavonoids against P. italicum was affected by the conjugation site of glycosylation and the class of sugar moiety. The correlation between antifungal activity and the inhibition of respiration of 5,7-dihydroxyflavonoids was further evaluated. We find no significant relationship among the IC50 of 5,7-dihydroxyflavonoids on spore germination and on respiration. Some 5,7-dihydroxyflavonoids even enhance the respiration of P. italicum. This indicate respiration is not the only target for 5,7-dihydroxyflavonoids against P. italicum.

Methylation of flavonoids: Chemical structures, bioactivities, progress and perspectives for biotechnological production

Among the natural products, flavonoids have been particularly attractive, highly studied and become one of the most important promising agent to treat cancer, oxidant stress, pathogenic bacteria, inflammations, cardio-vascular dysfunctions, etc. Despite many promising roles of flavonoids, expectations have not been fulfilled when studies were extended to the in vivo condition, particularly in humans. Instability and very low oral bioavailability of dietary flavonoids are the reasons behind this. Researches have demonstrated that the methylation of these flavonoids could increase their promise as pharmaceutical agents leading to novel applications. Methylation of the flavonoids via theirs free hydroxyl groups or C atom dramatically increases their metabolic stability and enhances the membrane transport, leading to facilitated absorption and highly increased oral bioavailability. In this paper, we concentrated on analysis of flavonoid methoxides including O- and C-methoxide derivatives in aspect of structure, bioactivities and description of almost all up-to-date O- and C-methyltransferases' enzymatic characteristics. Furthermore, modern biological approaches for synthesis and production of flavonoid methoxides using metabolic engineering and synthetic biology have been focused and updated up to 2015. This review will give a handful information regarding the methylation of flavonoids, methyltransferases and biotechnological synthesis of the same.

Use of active extracts of poplar buds against Penicillium italicum and possible modes of action

Antifungal components, from poplar buds active fraction (PBAF) against Penicillium italicum, the causal agent of blue mold in citrus fruits, were identified and possible action modes were investigated. Pinocembrin, chrysin and galangin were determined as active components in PBAF, using HPLC and HPLC-MS analysis. The antifungal activity is stable at temperatures ranging from 4 °C to 100 °C and pH levels ranging from 4 to 8. In the presence of PBAF, the hyphae become shriveled, wrinkled and the cell membrane became seriously disrupted. Further investigation on cell permeability, nucleic acid content and alkaline phosphatase suggest that the cell membrane might be the target. Mycelial oxygen consumption and the respiration-related enzymatic activity of succinate dehydrogenase, malate dehydrogenase and ATPase were all inhibited by PBAF. We propose that PBAF is a potentially useful alternative for blue mold control and may act against P. italicum by interfering with respiration and disrupting the cell membrane.

Caffeic Acid phenethyl ester and ethanol extract of propolis induce the complementary cytotoxic effect on triple-negative breast cancer cell lines

Chemotherapy of breast cancer could be improved by bioactive natural substances, which may potentially sensitize the carcinoma cells’ susceptibility to drugs. Numerous phytochemicals, including propolis, have been reported to interfere with the viability of carcinoma cells. We evaluated the in vitro cytotoxic activity of ethanol extract of propolis (EEP) and its derivative caffeic acid phenethyl ester (CAPE) towards two triple-negative breast cancer (TNBC) cell lines, MDA-MB-231 and Hs578T, by implementation of the MTT and lactate dehydrogenase (LDH) assays. The morphological changes of breast carcinoma cells were observed following exposure to EEP and CAPE. The IC₅₀ of EEP was 48.35 µg∙mL⁻¹ for MDA-MB-23 cells and 33.68 µg∙mL⁻¹ for Hs578T cells, whereas the CAPE IC₅₀ was 14.08 µM and 8.01 µM for the MDA-MB-231 and Hs578T cell line, respectively. Here, we report that propolis and CAPE inhibited the growth of the MDA-MB-231 and Hs578T lines in a dose-dependent and exposure time-dependent manner. EEP showed less cytotoxic activity against both types of TNBC cells. EEP and, particularly, CAPE may markedly affect the viability of breast cancer cells, suggesting the potential role of bioactive compounds in chemoprevention/chemotherapy by potentiating the action of standard anti-cancer drugs.