Identification of the Anti-Aflatoxinogenic Activity of Micromeria graeca and Elucidation of Its Molecular Mechanism in Aspergillus flavus

Effects of Different Solvents on the Total Phenol Content, Total Flavonoid Content, Antioxidant, and Antifungal Activities of Micromeria graeca L. from Middle Atlas of Morocco

Micromeria graeca L. is a dense chemical source of bioactive compounds such as phenolic compounds, which have various health-related properties. The current study aimed to investigate the impact of different extractor solvents on phenol and flavonoid contents, as well as the antioxidant and antifungal activities of different extracts. Initially, three extractor solvents (methanol, ethyl acetate, and water) were used to prepare the Soxhlet extracts, which were then examined for their polyphenolic content, flavonoid content, and antioxidant potential using three complementary assays (DPPH, FRAP, and TAC). The antifungal capacity against the two fungal strains (Candida albicans and Aspergillus niger) was performed using the method of diffusion on disc. The dosage of phytochemical compounds revealed that the highest values were established in water extract with values of 360 ± 22.1 mg GAE/g dry weight plant and 81.3 ± 21.2 mg RE/g dry weight plant for TPC and TFC, respectively. In addition, the strongest antioxidant activity measured by DPPH and FRAP assays was established in water extract with IC50 values of 0.33 ± 0.23 and 0.23 ± 0.12 mg/mL, respectively, while the methanol extract showed the best antioxidant activity as measured by TAC with an IC50 of 483 ± 17.6 mg GAEq/g dry weight plant. The water extract recorded the most important antifungal activity against Candida albicans with an inhibition zone of 16 ± 1.6 mm and MFC = 500 μg/mL, whereas ethyl acetate extract showed the lowest activity against both studied fungi strains. Micromeria graeca L. contains considerable amounts of bioactive contents with high antioxidant and antifungal potentials, which may make it a promising source of antioxidants and natural antifungal agents.

The latest advances on soy sauce research in the past decade: Emphasis on the advances in China

As an indispensable soybean-fermented condiment, soy sauce is extensively utilized in catering, daily cooking and food industry in East Asia and Southeast Asia and is becoming popular in the whole world. In the past decade, researchers began to pay great importance to the scientific research of soy sauce, which remarkably promoted the advances on fermentation strains, quality, safety, function and other aspects of soy sauce. Of them, the screening and reconstruction of Aspergillus oryzae with high-yield of salt and acid-tolerant proteases, mechanism of soy sauce flavor formation, improvement of soy sauce quality through the combination of novel physical processing technique and microbial/enzyme, separation and identification of soy sauce functional components are attracting more attention of researchers, and related achievements have been reported continually. Meanwhile, we pointed out the drawbacks of the above research and the future research directions based on published literature and our knowledge. We believe that this review can provide an insightful reference for international related researchers to understand the advances on soy sauce research.

Effect of Streptomyces roseolus Cell-Free Supernatants on the Fungal Development, Transcriptome, and Aflatoxin B1 Production of Aspergillus flavus

Crop contamination by aflatoxin B1 (AFB1), an Aspergillus-flavus-produced toxin, is frequently observed in tropical and subtropical regions. This phenomenon is emerging in Europe, most likely as a result of climate change. Alternative methods, such as biocontrol agents (BCAs), are currently being developed to reduce the use of chemicals in the prevention of mycotoxin contamination. Actinobacteria are known to produce many bioactive compounds, and some of them can reduce in vitro AFB1 concentration. In this context, the present study aims to analyze the effect of a cell-free supernatant (CFS) from Streptomyces roseolus culture on the development of A. flavus, as well as on its transcriptome profile using microarray assay and its impact on AFB1 concentration. Results demonstrated that in vitro, the S. roseolus CFS reduced the dry weight and conidiation of A. flavus from 77% and 43%, respectively, and was therefore associated with a reduction in AFB1 concentration reduction to levels under the limit of quantification. The transcriptomic data analysis revealed that 5198 genes were differentially expressed in response to the CFS exposure and among them 5169 were downregulated including most of the genes involved in biosynthetic gene clusters. The aflatoxins' gene cluster was the most downregulated. Other gene clusters, such as the aspergillic acid, aspirochlorine, and ustiloxin B gene clusters, were also downregulated and associated with a variation in their concentration, confirmed by LC-HRMS.

Role of Polyphenols from the Aqueous Extract of Aloysia citrodora in the Inhibition of Aflatoxin B1 Synthesis in Aspergillus flavus

Aflatoxin B1 (AFB1) is a mycotoxin considered a potent carcinogen for humans that contaminates a wide range of crops. Various strategies have been established to reduce or block the synthesis of AFB1 in food and feed. The use of aqueous extracts derived from plants with high antioxidant activity has been a subject of study in recent years due to their efficacy in inhibiting AFB1. In this study, we assessed the effect of Aloysia citrodora aqueous extract on Aspergillus flavus growth and on AFB1 production. A bio-guided fractionation followed by High Performance Liquid Chromatography (HPLC) and Mass spectrometry analysis of the active fraction were applied to identify the candidate molecules responsible for the dose-effect inhibition of AFB1 synthesis. Our results revealed that polyphenols are the molecules implicated in AFB1 inhibition, achieving almost a total inhibition of the toxin production (99%). We identified luteolin-7-diglucuronide as one of the main constituents in A. citrodora extract, and demonstrated that it is able to inhibit, by itself, AFB1 production by 57%. This is the first study demonstrating the anti-Aflatoxin B1 effect of this molecule, while other polyphenols surely intervene in A. citrodora anti-AFB1 activity.

Inhibition of Aflatoxin B1 Synthesis in Aspergillus flavus by Mate (Ilex paraguariensis), Rosemary (Rosmarinus officinalis) and Green Tea (Camellia sinensis) Extracts: Relation with Extract Antioxidant Capacity and Fungal Oxidative Stress Response Modulation

Plant extracts may represent an ecofriendly alternative to chemical fungicides to limit aflatoxin B1 (AFB1) contamination of foods and feeds. Mate (Ilex paraguariensis), rosemary (Romarinus officinalis) and green tea (Camellia sinensis) are well known for their beneficial properties, which are mainly related to their richness in bioactive phenolic compounds. AFB1 production is inhibited, with varying efficiency, by acetone/water extracts from these three plants. At 0.45 µg dry matter (DM)/mL of culture medium, mate and green tea extracts were able to completely inhibit AFB1 production in Aspergillus flavus, and rosemary extract completely blocked AFB1 biosynthesis at 3.6 µg DM/mL of culture medium. The anti-AFB1 capacity of the extracts correlated strongly with their phenolic content, but, surprisingly, no such correlation was evident with their antioxidative ability, which is consistent with the ineffectiveness of these extracts against fungal catalase activity. Anti-AFB1 activity correlated more strongly with the radical scavenging capacity of the extracts. This is consistent with the modulation of SOD induced by mate and green tea in Aspergillus flavus. Finally, rutin, a phenolic compound present in the three plants tested in this work, was shown to inhibit AFB1 synthesis and may be responsible for the anti-mycotoxin effect reported herein.

Antifungal and antimycotoxic activities of 3 essential oils against 3 mycotoxinogenic fungi

Fungal toxins can have various adverse health effects, including carcinogenic, teratogenic or hepatotoxic impacts. In addition, fungal alteration has also a negative impact on agricultural plant production. The use of chemical fungicides to control mycotoxin contamination is increasingly controversial and regulated. More environmentally friendly methods are therefore being explored. Essential oils, as compounds extracted from plants, are liquids whose specific aromatic compounds give each essential oil its own unique characteristics. Due to their rich chemical composition, essential oils (EOs) have many interesting properties, including antifungal activities. The objective of the present study was to analyze volatile chemical composition of EOs (Cymbopogon schoenanthus, Cymbopogon nardus and Eucalyptus camaldulensis) by GC/MS and to investigate their effects on the growth, sporulation and mycotoxin production of Aspergillus flavus, Aspergillus carbonarius and Fusarium verticillioides (aflatoxin B1, ochratoxin A and fumonisin B1, respectively). In addition, EOs influence on aflatoxin B1 (AFB1) and fumonisin B1 (FB1) biosynthesis pathways was explored using real-time qRT-PCR. The results obtained in vitro, by direct contact with the EOs and by diffusion of their volatile compounds, showed that the essential oils had inhibitory effects on the growth and the production of mycotoxins of the 3 fungal strains and modified the expression of some toxin synthesis genes. We conclude that the recorded effects were dependent on the combined effects of the EOs type, the fungal strains and the doses studied.

A methanolic extract of Zanthoxylum bungeanum modulates secondary metabolism regulator genes in Aspergillus flavus and shuts down aflatoxin production

Aflatoxin B1 (AFB1) is a food-borne toxin produced by Aspergillus flavus and a few similar fungi. Natural anti-aflatoxigenic compounds are used as alternatives to chemical fungicides to prevent AFB1 accumulation. We found that a methanolic extract of the food additive Zanthoxylum bungeanum shuts down AFB1 production in A. flavus. A methanol sub-fraction (M20) showed the highest total phenolic/flavonoid content and the most potent antioxidant activity. Mass spectrometry analyses identified four flavonoids in M20: quercetin, epicatechin, kaempferol-3-O-rhamnoside, and hyperoside. The anti-aflatoxigenic potency of M20 (IC₅₀: 2-4 µg/mL) was significantly higher than its anti-proliferation potency (IC₅₀: 1800-1900 µg/mL). RNA-seq data indicated that M20 triggers significant transcriptional changes in 18 of 56 secondary metabolite pathways in A. flavus, including repression of the AFB1 biosynthesis pathway. Expression of aflR, the specific activator of the AFB1 pathway, was not changed by M20 treatment, suggesting that repression of the pathway is mediated by global regulators. Consistent with this, the Velvet complex, a prominent regulator of secondary metabolism and fungal development, was downregulated. Decreased expression of the conidial development regulators brlA and Medusa, genes that orchestrate redox responses, and GPCR/oxylipin-based signal transduction further suggests a broad cellular response to M20. Z. bungeanum extracts may facilitate the development of safe AFB1 control strategies.

Effects of Chinese Gallnut Tannic Acid on Growth Performance, Blood Parameters, Antioxidative Status, Intestinal Histomorphology, and Cecal Microbial Shedding in Broilers Challenged with Aflatoxin B1

The objective of the present study was to investigate the effects of tannic acid (TA) on growth performance, blood parameters, antioxidant capacity, and intestinal health in broilers challenged with aflatoxin B1 (AFB1). A total of 480 1-d-old broilers were randomly allotted into 4 treatments: 1) CON, control diet, 2) AF, CON + 60 μg/kg AFB1 of feed during d 1 to 21, CON + 120 μg/kg AFB1 of feed during d 22 to 42, 3) TA1, AF +250 mg/kg TA, 4) TA2, AF +500 mg/kg TA. Average daily gain (ADG) and average daily feed intake (ADFI) were increased in the TA1 during d 1 to 21, d 22 to 42 and d1 to 42 compared with CON and AF treatments (P < 0.05). Broilers fed the TA2 diet had greater ADG and ADFI than those fed the CON and AF diets during the finisher and the whole period (P < 0.05). Administration of TA decreased the relative weight of liver and kidney compared with broilers fed the AF diet on d 42 (P < 0.05). The blood activity of alanine transferase (ALT) and gamma-glutamyl transferase (GGT) was increased in the AF treatment compared with the CON (P < 0.05). Broilers fed the TA1 decreased the ALT content on d 21, and the level of ALT and GGT was decreased in the TA2 compared with the AF group on d 42 (P < 0.05). The activity of total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) in plasma, and the hepatic glutathione S-transferase (GST) was decreased in the AF group compared with the CON group (P < 0.05). The TA decreased plasma malondialdehyde concentration, and increased plasma T-SOD, GSH-Px, total antioxidant capacity, and hepatic GST activity compared to the AF (P < 0.05). The crypt depth of jejunum was decreased in the TA1 treatment on d 21, and the villus height of ileum was increased in the TA2 group on d 42 compared with the AF treatment (P < 0.05). The cecal Lactobacillus counts on d 21 was tended to increase in the TA treatments compared with the AF (P = 0.061). In conclusion, dietary inclusion of 250 mg/kg and 500 mg/kg TA could improve the growth, antioxidant capacity, and partially protected the intestinal health of broilers challenged with AFB1.

The Solvent Dimethyl Sulfoxide Affects Physiology, Transcriptome and Secondary Metabolism of Aspergillus flavus

Dimethyl sulfoxide (DSMO) is a simple molecule widely used because of its great solvating ability, but this solvent also has little-known biological effects, especially on fungi. Aspergillus flavus is a notorious pathogenic fungus which may contaminate a large variety of crops worldwide by producing aflatoxins, endangering at the same time food safety and international trade. The aim of this study was to characterize the effect of DMSO on A. flavus including developmental parameters such as germination and sporulation, as well as its transcriptome profile using high-throughput RNA-sequencing assay and its impact on secondary metabolism (SM). After DMSO exposure, A. flavus displayed depigmented conidia in a dose-dependent manner. The four-day exposition of cultures to two doses of DMSO, chosen on the basis of depigmentation intensity (35 mM “low” and 282 mM “high”), led to no significant impact on fungal growth, germination or sporulation. However, transcriptomic data analysis showed that 4891 genes were differentially regulated in response to DMSO (46% of studied transcripts). A total of 4650 genes were specifically regulated in response to the highest dose of DMSO, while only 19 genes were modulated upon exposure to the lowest dose. Secondary metabolites clusters genes were widely affected by the DMSO, with 91% of clusters impacted at the highest dose. Among these, aflatoxins, cyclopiazonic acid and ustiloxin B clusters were totally under-expressed. The genes belonging to the AFB1 cluster were the most negatively modulated ones, the two doses leading to 63% and 100% inhibition of the AFB1 production, respectively. The SM analysis also showed the disappearance of ustiloxin B and a 10-fold reduction of cyclopiazonic acid level when A. flavus was treated by the higher DMSO dose. In conclusion, the present study showed that DMSO impacted widely A. flavus’ transcriptome, including secondary metabolism gene clusters with the aflatoxins at the head of down-regulated ones. The solvent also inhibits conidial pigmentation, which could illustrate common regulatory mechanisms between aflatoxins and fungal pigment pathways. Because of its effect on major metabolites synthesis, DMSO should not be used as solvent especially in studies testing anti-aflatoxinogenic compounds.

Antifungal and anti-aflatoxigenic properties of organs of Cannabis sativa L.: relation to phenolic content and antioxidant capacities

Aflatoxin B1 is a carcinogenic mycotoxin that frequently contaminates crops worldwide. Current research indicates that the use of natural extracts to combat mycotoxin contamination may represent an eco-friendly, sustainable strategy to ensure food safety. Although Cannabis sativa L. has long been known for its psychoactive cannabinoids, it is also rich in many other bioactive molecules. This study examines extracts from various organs of Cannabis sativa L. to determine their ability to limit aflatoxin production and growth of Aspergillus flavus. The results indicate that flower extract is most effective for limiting the synthesis of aflatoxin B1, leading to an almost-complete inhibition of toxin production at a concentration of 0.225 mg dry matter per gram of culture medium. Since flower extract is rich in phenolic compounds, its total antioxidant ability and radical-scavenging capacity are determined. Compared with other anti-aflatoxigenic extracts, the anti-oxidative potential of Cannabis sativa L. flower extract appears moderate, suggesting that its anti-mycotoxin effect may be related to other bioactive compounds.

Mimosa tenuiflora Aqueous Extract: Role of Condensed Tannins in Anti-Aflatoxin B1 Activity in Aspergillus flavus

Aflatoxin B1 (AFB1) is a potent carcinogenic mycotoxin that contaminates numerous crops pre- and post-harvest. To protect foods and feeds from such toxins without resorting to pesticides, the use of plant extracts has been increasingly studied. The most interesting candidate plants are those with strong antioxidative activity because oxidation reactions may interfere with AFB1 production. The present study investigates how an aqueous extract of Mimosa tenuiflora bark affects both the growth of Aspergillus flavus and AFB1 production. The results reveal a dose-dependent inhibition of toxin synthesis with no impact on fungal growth. AFB1 inhibition is related to a down-modulation of the cluster genes of the biosynthetic pathway and especially to the two internal regulators aflR and aflS. Its strong anti-oxidative activity also allows the aqueous extract to modulate the expression of genes involved in fungal oxidative-stress response, such as msnA, mtfA, atfA, or sod1. Finally, a bio-guided fractionation of the aqueous extract demonstrates that condensed tannins play a major role in the anti-aflatoxin activity of Mimosa tenuiflora bark.

The Potential of Plant-Based Bioactive Compounds on Inhibition of Aflatoxin B1 Biosynthesis and Down-regulation of aflR, aflM and aflP Genes

The use of plant extracts in pre- and post-harvest disease management of agricultural crops to cope with aflatoxin B1 contamination has shown great promise due to their capability in managing toxins and safe-keeping the quality. We investigated the anti-aflatoxigenic effect of multiple doses of eight plant extracts (Heracleum persicum, Peganum harmala, Crocus sativus, Trachyspermum ammi, Rosmarinus officinalis, Anethum graveolens, Berberis vulgaris, Berberis thunbergii) on Aspergillus flavus via LC-MS and the down-regulatory effect of them on aflR, aflM and aflP genes involved in the aflatoxin B1 biosynthesis pathway using RT-qPCR analyses. Our results showed that H. persicum (4 mg/mL), P. harmala (6 mg/mL) and T. ammi (2 mg/mL) completely stopped the production of aflatoxin B1, without inducing significant changes in A. flavus growth. Furthermore, our findings showed a highly significant correlation between the gene expression and the aflatoxin B1 biosynthesis, such that certain doses of the extracts reduced or blocked the expression of the aflR, aflM and aflP and consequently reduced the synthesis of aflatoxin B1. Interestingly, compared to the regulatory gene (aflR), the down-regulation of expression in the structural genes (aflM and aflP) was more consistent and correlated with the inhibition of aflatoxin B1 production. Overall, this study reveals the anti-aflatoxigenic mechanisms of the selected plant extracts at the gene expression level and provides evidence for their use in plant and crop protection.

Chemical repertoire and biosynthetic machinery of the Aspergillus flavus secondary metabolome: A review

Filamentous fungi represent a rich source of extrolites, including secondary metabolites (SMs) comprising a great variety of astonishing structures and interesting bioactivities. State-of-the-art techniques in genome mining, genetic manipulation, and secondary metabolomics have enabled the scientific community to better elucidate and more deeply appreciate the genetic and biosynthetic chemical arsenal of these microorganisms. Aspergillus flavus is best known as a contaminant of food and feed commodities and a producer of the carcinogenic family of SMs, aflatoxins. This fungus produces many SMs including polyketides, ribosomal and nonribosomal peptides, terpenoids, and other hybrid molecules. This review will discuss the chemical diversity, biosynthetic pathways, and biological/ecological role of A. flavus SMs, as well as their significance concerning food safety and security.

Transcriptome Sequencing Revealed an Inhibitory Mechanism of Aspergillus flavus Asexual Development and Aflatoxin Metabolism by Soy-Fermenting Non-Aflatoxigenic Aspergillus

Aflatoxins (AFs) have always been regarded as the most effective carcinogens, posing a great threat to agriculture, food safety, and human health. Aspergillus flavus is the major producer of aflatoxin contamination in crops. The prevention and control of A. flavus and aflatoxin continues to be a global problem. In this study, we demonstrated that the cell-free culture filtrate of Aspergillus oryzae and a non-aflatoxigenic A. flavus can effectively inhibit the production of AFB1 and the growth and reproduction of A. flavus, indicating that both of the non-aflatoxigenic Aspergillus strains secrete inhibitory compounds. Further transcriptome sequencing was performed to analyze the inhibitory mechanism of A. flavus treated with fermenting cultures, and the results revealed that genes involved in the AF biosynthesis pathway and other biosynthetic gene clusters were significantly downregulated, which might be caused by the reduced expression of specific regulators, such as AflS, FarB, and MtfA. The WGCNA results further revealed that genes involved in the TCA cycle and glycolysis were potentially involved in aflatoxin biosynthesis. Our comparative transcriptomics also revealed that two conidia transcriptional factors, brlA and abaA, were found to be significantly downregulated, which might lead to the downregulation of conidiation-specific genes, such as the conidial hydrophobins genes rodA and rodB. In summary, our research provides new insights for the molecular mechanism of controlling AF synthesis to control the proliferation of A. flavus and AF pollution.

Antihyperglycemic Activity of Micromeria graeca Aqueous Extract in Streptozotocin-Induced Diabetic Rats

AIM

This study aimed to investigate the effect of Micromeria graeca on blood glucose levels and lipid parameters in an experimental model of diabetes.

BACKGROUND

Micromeria graeca (L.) Benth. ex Rchb is a medicinal plant used in Morocco for the treatment of several pathologies including diabetes.

OBJECTIVE

This study aimed to evaluate the antihyperglycemic and antihyperlipidemic effects of the aqueous extract of Micromeria graeca (M. graeca) aerial parts (AEMG) under physiological (normal rats) and pathological (STZ-induced diabetic rats) conditions. Additionally, we analyzed the phytochemical composition and antioxidant capacity.

METHODS

The effects of the acute and sub-chronic administration of AEMG (20 mg/kg) on blood glucose levels and lipid profiles were evaluated in normal and streptozotocin-induced diabetic rats. Moreover, the phytochemical analysis was carried with standard tests and estimation of total phenolics compounds by Folin-Ciocalteu reagent. The antioxidant activity was realized by the DPPH method.

RESULTS

Single oral administration of M. graeca aqueous extract decreased blood glucose levels 4 and 6 hours (p<0.01) after treatment in diabetic rats. In accordance, the repeated oral administration of M. graeca showed a significant reduction in blood glucose levels in diabetic rats since the second day to the end of the period experiment (p<0.0001). In addition, two weeks of treatment with M. graeca reduced total cholesterol levels (p<0.05) with a significant increase of HDL-c level (p<0.01) in diabetic rats. Moreover, M. graeca scavenged DPPH radical in a dose-dependent manner (IC50=0.48 mg/ml), whereas IC50 was 0.55 mg/ml for BHT. Phytochemical analysis showed the richness of Micromeria graeca on polyphenols (281.94±4.61 mg GAE/1 g), flavonoids, tannins, glycosides, saponins, sterols, sesquiterpenes, and terpenoids.

CONCLUSION

AEMG exhibits antihyperglycemic and antihyperlipidemic activities in STZ-induced diabetic rats and a potent antioxidant capacity.

Aflatoxin Biosynthesis and Genetic Regulation: A Review

The study of fungal species evolved radically with the development of molecular techniques and produced new evidence to understand specific fungal mechanisms such as the production of toxic secondary metabolites. Taking advantage of these technologies to improve food safety, the molecular study of toxinogenic species can help elucidate the mechanisms underlying toxin production and enable the development of new effective strategies to control fungal toxicity. Numerous studies have been made on genes involved in aflatoxin B1 (AFB1) production, one of the most hazardous carcinogenic toxins for humans and animals. The current review presents the roles of these different genes and their possible impact on AFB1 production. We focus on the toxinogenic strains Aspergillus flavus and A. parasiticus, primary contaminants and major producers of AFB1 in crops. However, genetic reports on A. nidulans are also included because of the capacity of this fungus to produce sterigmatocystin, the penultimate stable metabolite during AFB1 production. The aim of this review is to provide a general overview of the AFB1 enzymatic biosynthesis pathway and its link with the genes belonging to the AFB1 cluster. It also aims to illustrate the role of global environmental factors on aflatoxin production and the recent data that demonstrate an interconnection between genes regulated by these environmental signals and aflatoxin biosynthetic pathway.

G-protein-coupled Receptors in Fungi

G-protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors in fungi. These receptors have an important role in the transduction of extracellular signals into intracellular sites in response to diverse stimuli. They enable fungi to coordinate cell function and metabolism, thereby promoting their survival and propagation, and sense certain fundamentally conserved elements, such as nutrients, pheromones, and stress, for adaptation to their niches, environmental stresses, and host environment, causing disease and pathogen virulence. This chapter highlights the role of GPCRs in fungi in coordinating cell function and metabolism. Fungal cells sense the molecular interactions between extracellular signals. Their respective sensory systems are described here in detail.

Cardiovascular Effects of Micromeria graeca (L.) Benth. ex Rchb in Normotensive and Hypertensive Rats

AIMS

The present study was performed in order to analyze the antihypertensive activity of Micromeria graeca (L.) Benth. ex Rchb.

BACKGROUND

Micromeria graeca (L.) Benth. ex Rchb is an aromatic and medicinal plant belonging to the Lamiaceae family. This herb is used to treat various pathologies such as cardiovascular disorders. Meanwhile, its pharmacological effects on the cardiovascular system have not been studied.

OBJECTIVE

The present study aimed to evaluate the effect of aqueous extract of aerial parts of Micromeria graeca (AEMG) on the cardiovascular system in normotensive and hypertensive rats.

METHODS

In this study, the cardiovascular effect of AEMG was evaluated using in vivo and in vitro investigations. In order to assess the acute effect of AEMG on the cardiovascular system, anesthetized L-NAME-hypertensive and normotensive rats received AEMG (100 mg/kg) orally and arterial blood pressure parameters were monitored during six hours. In the sub-chronic study, rats were orally treated for one week, followed by blood pressure assessment during one week of treatment. Blood pressure was measured using a tail-cuff and a computer-assisted monitoring device. In the second experiment, isolated rat aortic ring pre-contracted with Epinephrine (EP) or KCl was used to assess the vasorelaxant effect of AEMG.

RESULTS

Oral administration of AEMG (100 mg/kg) provoked a decrease of arterial blood pressure parameters in hypertensive rats. In addition, AEMG induced a vasorelaxant effect in thoracic aortic rings pre-contracted with EP (10 μM) or KCl (80 mM). This effect was attenuated in the presence of propranolol and methylene blue. While in the presence of glibenclamide, L-NAME, nifedipine or Indomethacin, the vasorelaxant effect was not affected.

CONCLUSION

This study showed that Micromeria graeca possesses a potent antihypertensive effect and relaxes the vascular smooth muscle through β-adrenergic and cGMP pathways.

Research progress on the basic helix-loop-helix transcription factors of Aspergillus species

Basic helix-loop-helix (bHLH) proteins belong to a superfamily of transcription factors, and they are widely distributed in eukaryotic organisms. Members of the bHLH protein family can form homodimers or heterodimers with themselves or other family members, and they often play bifunctional roles as activators and repressors to uniquely regulate the transcription of downstream target genes. The bHLH transcription factors are usually involved in developmental processes, including cellular proliferation and differentiation. Therefore, these transcription factors often play crucial roles in regulating growth, development, and differentiation in eukaryotes. Aspergillus species fungi are widely distributed in the environment, and they play important roles not only in the decomposition of organic matter as an important environmental microorganism but also in the fermentation and the food processing industry. Furthermore, some pathogenic fungi, such as Aspergillus flavus and Aspergillus fumigatus, affect the environment and human health in important ways. Recent research has shown that some Aspergillus bHLH proteins are significantly involved in the regulation of asexual and sexual reproduction, secondary metabolite production, carbohydrate metabolism, conidial and sclerotial production, among other processes. Here, we review the regulatory mechanisms and biological functions of the bHLH transcription factors of the Aspergillus genus to provide a theoretical reference for further study on the growth and development of Aspergillus and the functions of bHLHs.

Comparison of Phenolic Contents and Biological Potential of Different Polar Extracts of Micromeria graeca, from Algeria

Methods:

The total phenolic and flavonoid contents were determined by the Folin-Ciocalteu and aluminium chloride methods, respectively. The antioxidant capacity of the extracts was evaluated using three different assays. The antifungal capacity against the two strains Candida albicans and Aspergillus niger by using the method of diffusion on disc was also carried out.

Results:

The 50% acetonic extract gave a better rate of extraction which is 14.4% and presents the highest contents in total phenolics and flavonoids which are of 46.7 &#177; 2.3 mg gallic acid equivalent /g dry matter and 2.4 &#177; 0.1 mg quercetin equivalent/g dry matter respectively. A better antioxidant activity for the various tests was observed for 50% methanolic and acetonic extracts. The extract of 50% acetone recorded the most important antifungal activity.

Conclusion:

The findings of this study showed that the extract prepared with the 50% acetone from Micromeria graeca has the highest phenolics content and revealed the best biological activities. So, this study has allowed us to find the suitable solvent for the preparation of the M. graeca extract for several uses.

Streptomyces roseolus, A Promising Biocontrol Agent Against Aspergillus flavus, the Main Aflatoxin B₁ Producer

Crop contamination by aflatoxin B₁ is a current problem in tropical and subtropical regions. In the future, this contamination risk may be expanded to European countries due to climate change. The development of alternative strategies to prevent mycotoxin contamination that further contribute to the substitution of phytopharmaceutical products are thus needed. For this, a promising method resides in the use of biocontrol agents. Several actinobacteria strains have demonstrated to effectively reduce the aflatoxin B₁ concentration. Nevertheless, the molecular mechanism of action by which these biological agents reduce the mycotoxin concentration has not been determined. The aim of the present study was to test the potential use of Streptomyces roseolus as a biocontrol agent against aflatoxin B₁ contamination. Co-cultures with Aspergillus flavus were conducted, and the molecular fungal response was investigated through analyzing the q-PCR expression of 65 genes encoding relevant fungal functions. Moreover, kojic and cyclopiazonic acid concentrations, as well as morphological fungal changes were also analyzed. The results demonstrated that reduced concentrations of aflatoxin B₁ and kojic acid were respectively correlated with the down-regulation of the aflatoxin B₁ gene cluster and kojR gene expression. Moreover, a fungal hypersporulated phenotype and a general over-expression of genes involved in fungal development were observed in the co-culture condition.

OTA Prevention and Detoxification by Actinobacterial Strains and Activated Carbon Fibers: Preliminary Results

Ochratoxin A (OTA) is a mycotoxin produced by several species of Aspergillus and Penicillium that contaminate food and feed raw materials. To reduce OTA contamination, we first tested in vitro, actinobacterial strains as potential biocontrol agents and afterward, through a physical decontamination method using activated carbon fibers (ACFs). Actinobacterial strains were screened for their ability to reduce OTA in solid co-culture with A. carbonarius, which is the major OTA-producing species in European vineyards. Four strains showed a high affinity for removing OTA (67%–83%) with no significant effect on fungal growth (<20%). The mechanism of action was first studied by analyzing the expression of OTA cluster genes (acOTApks, acOTAnrps, acOTAhal) by RT-qPCR showing a drastic reduction in all genes (7–15 times). Second, the ability of these strains to degrade OTA was assessed in vitro on ISP2 solid medium supplemented with OTA (100 µg/L). Two strains reduced OTA to undetectable levels. As for the physical method, high adsorption rates were obtained for ACFs at 0.8 g/L with a 50% adsorption of OTA in red wine by AC15 and 52% in grape juice by AC20 within 24 h. These promising methods could be complementarily applied toward reducing OTA contamination in food chains, which promotes food safety and quality.

Promising Detoxification Strategies to Mitigate Mycotoxins in Food and Feed

Mycotoxins are secondary fungal metabolites associated with adverse human health and animal productivity consequences.[...].