Promising Antileishmanial Activity of Micromeria nervosa Essential Oil: In Vitro and In Silico Studies.

The present study aimed to evaluate the leishmanicidal potential of the essential oil (EO) of Micromeria (M.) nervosa and to investigate its molecular mechanism of action by qPCR. Furthermore, in silicointeraction study of the major M. nervosa EO compounds with the enzyme cytochrome P450 sterol 14α-demethylase (CYP51) was also performed. M. nervosa EO was analyzed by gas chromatography-mass spectrometry (GC-MS). Results showed that α-pinene (26.44%), t-cadinol (26.27%), caryophyllene Oxide (7.73 ± 1.04%), and α-Cadinene (3.79 ± 0.12%) are the major compounds of M. nervosa EO. However, limited antioxidant activity was observed, as this EO was ineffective in neutralizing DPPH free radicals and in inhibiting ß-carotene bleaching. Interestingly, it displayed effective leishmanicidal potential against promastigote (IC50 of 6.79 and 5.25 µg/mL) and amastigote (IC50 of 8.04 and 7.32 µg/mL) forms of leishmania (L.) infantum and L. major, respectively. Molecular mechanism investigation showed that M. nervosa EO displayed potent inhibition on the thiol regulatory pathway. Furthermore, a docking study of the main components of the EO with cytochrome P450 sterol 14α-demethylase (CYP51) enzyme revealed that t-cadinol exhibited the best binding energy values (-7.5 kcal/mol), followed by α-cadinene (-7.3 kcal/mol) and caryophyllene oxide (-7 kcal/mol). These values were notably higher than that of the conventional drug fluconazole showing weaker binding energy (-6.9 kcal/mol). These results suggest that M. nervosa EO could serve as a potent and promising candidate for the development of alternative antileishmanial agent in the treatment of leishmaniasis.

Antioxidant, antibacterial, and antileishmanial potential of Micromeria nervosa extracts and molecular mechanism of action of the bioactive compound.

AIMS: This study aimed to determine the antibacterial and antileishmanial potential of Micromeria nervosa extracts. The identification of the antileishmanial compound and the study of its molecular mechanism of action have also been undertaken. METHODS AND RESULTS: Ethanol extract showed high polyphenol content and diethyl ether extract exhibited high DPPH scavenging and low beta-carotene bleaching activity (IC50 = 13.04 ± 0.99 and 200.18 ± 3.32 µg mL-1, respectively). However, diethyl ether extract displayed high antibacterial activity against Gram-positive strains including methicillin-resistant Staphylococcus aureus (MIC = 31.25 µg mL-1), Staph. aureus ATCC6538 (MIC = 62.5 µg mL-1), and Listeria monocytogenes ATCC 19115 (MIC = 125 µg mL-1), as well as high antileishmanial activity against the promastigote forms of L. infantum and L. major (IC50 = 11.45 and 14.53 µg mL-1, respectively). The active compound was purified using bioassay-guided fractionation and thin layer chromatography, and identified as ursolic acid using high-performance liquid chromatography coupled with a photodiode array and mass spectrometry. The purified compound was strongly inhibitory against the promastigote and amastigote forms of L. infantum and L. major (IC50 = 5.87 and 6.95 µg mL-1 versus 9.56 and 10. 68 µg mL-1, respectively) without overt cytotoxicity against Raw 264.7 macrophage cells (SI = 13.53 and 11.43, respectively). The commercial compound (ursolic acid) showed similar activity against amastigotes and promastigotes forms of L. infantum and L. major. Moreover, its molecular mode of action against leishmaniasis seems to involve the expression of the ODC and SPS genes involved in thiol pathway. CONCLUSION: Extracts of M. nervosa can be considered as a potential alternative to antimicrobial and antileishmanial drugs.

Anti-Candida and Anti-Leishmanial Activities of Encapsulated Cinnamomum verum Essential Oil in Chitosan Nanoparticles.

Nanoencapsulation is widely considered as a highly effective strategy to enhance essential oils' (EO) stability by protecting them from oxidative deterioration and evaporation. The present study aims to optimize and characterize an efficient technique for encapsulating Cinnamomum (C.) verum essential oil into chitosan nanoparticles using response surface methodology (RSM). Moreover, the optimized C. verum EO nanoparticle was investigated for its antibacterial (against Gram-positive and Gram-negative bacteria), antifungal (against Candida albicans), and antiparasitic activity (against Leishmania parasites). Five parameters were investigated using a Plackett-Burman and Box-Behnken statistical design: the chitosan molecular weight, TPP concentration, C. verum EO/chitosan ratio, mixing method, and the duration of the reaction. Encapsulation efficiency and anti-candida activity were considered as responses. The antibacterial, anticandidal, and anti-leishmanial activities were also assessed using a standard micro-broth dilution assay and the cytotoxicity assay was assessed against the macrophage cell line RAW 264.7. The optimized nanoparticles were characterized using Fourier transform infrared spectroscopy, Zeta potential, and scanning electron microscopy. The study results indicated that under optimal conditions, the nanoencapsulation of C. verum EO into chitosan nanoparticles resulted in an encapsulation efficiency of 92.58%, with a regular distribution, a nanoparticle size of 480 ± 14.55 nm, and a favorable Zeta potential of 35.64 ± 1.37 mV. The optimized C. verum EO/chitosan nanoparticles showed strong antifungal activity against C. albicans pathogens (CMI = 125 µg mL-1), notable antibacterial activity against both Gram-positive and Gram-negative bacteria (ranging from 125 to 250 µg mL-1), high leishmanicidal potential against the promastigotes form of L. tropica and L. major (IC50 = 10.47 and 15.09 µg mL-1, respectively), and a four-fold cytotoxicity reduction compared to non-encapsulated essential oil. These results suggest that C. verum EO-loaded chitosan nanoparticles could be a promising delivery system for the treatment of cutaneous Candida albicans infections.

Datura stramonium Flowers as a Potential Natural Resource of Bioactive Molecules: Identification of Anti-Inflammatory Agents and Molecular Docking Analysis.

The present study investigated the antioxidant, antibacterial, antiviral and anti-inflammatory activities of different aerial parts (flowers, leaves and seeds) of Datura stramonium. The plant material was extracted with 80% methanol for about 24 h. The sensitivity to microorganisms analysis was performed by the microdilution technique. Antioxidant tests were performed by scavenging the DPPH and ABTS radicals, and by FRAP assay. Anti-inflammatory activity was evaluated through the inhibition of nitric oxide production in activated macrophage RAW 264.7 cells. Cell viability was assessed with an MTT assay. Results show that the flower extract revealed a powerful antimicrobial capacity against Gram-positive bacteria and strong antioxidant and anti-inflammatory activities. No significant cytotoxicity to activated macrophages was recorded. High resolution electrospray ionization mass spectrometry and nuclear magnetic resonance analysis identified two molecules with important anti-inflammatory effects: 12α-hydroxydaturametelin B and daturametelin B. Molecular docking analysis with both pro-inflammatory agents tumor necrosis factor alpha and interleukin-6 revealed that both compounds showed good binding features with the selected target proteins. Our results suggest that D. stramonium flower is a promising source of compounds with potential antioxidant, antibacterial, and anti-inflammatory activities. Isolated withanolide steroidal lactones from D. stramonium flower extract with promising anti-inflammatory activity have therapeutic potential against inflammatory disorders.

Synergistic combination of Cinnamomum verum and Syzygium aromaticum treatment for cutaneous leishmaniasis and investigation of their molecular mechanism of action.

Combination therapy at appropriately suitable doses presents a promising alternative to monotherapeutic drugs. In this study, Cinnamomum verum and Syzygium aromaticum essential oils and their major compounds have exhibited substantial leishmaniacidal potential against both promastigote and amastigote forms of Leishmania (L.) major. However, they displayed high cytotoxicity against Raw264.7 macrophage cells. Interestingly, when combined with each other or with amphotericin B, they demonstrated a synergistic effect (FIC<0.5) with low cytotoxicity. These combinations are able to modulate the production of nitric oxide (NO) by macrophages. Notably, the combination of S. aromaticum Essential oil with amphotericin B stimulates macrophage cells by increasing NO production to eliminate leishmanial parasites. Furthermore, investigation of the molecular mechanism of action of these synergistic combinations reveals potent inhibition of the sterol pathway through the inhibition of the CYP51 gene expression. The findings suggest that combination therapy may offer significant therapeutic benefits in both food and pharmaceutical fields.

Antimicrobial, antioxidant and antileishmanial activities of Ziziphus lotus leaves.

The aim of this study was to investigate antimicrobial and antioxidant activities of different fractions obtained from edible Tunisian Ziziphus Lotus leaves of Tozeur region. Different organic extracts were tested: cyclohexane, dichloromethane, ethyl acetate, n-butanol and water. Bio-guided fractionation revealed that dichloromethane fraction is the most active against S. aureus and Methicillin-resistant S. aureus strains. Moreover, this fraction showed the highest antileishmanial activity with IC50 values of 20.55 ± 0.34 µg/mL and 15.37 ± 0.17 µg/mL against L. major and L. infantum, respectively. The potentialities of antibacterial and leishmanicidal activities found in dichloromethane could be explained by the presence of major flavonoids such as catechin, rutin and luteolin 7-O-glucoside as revealed by HPLC system. The observed moderate antifungal activity, which was only given by butanolic fraction against pathogen fungi, may be attributed to the presence of chlorogenic acid. Furthermore, dichloromethane and butanolic fraction showed a good DPPH (2,2-diphenyl-1-picryl hydrazyl) scavenging activity and Ferric reducing power. These results suggest that Ziziphus lotus leaf fractions might be used as antioxidant and antimicrobialagent.

Antibacterial and antibiofilm activity of Peganum harmala seed extract against multidrug-resistant Pseudomonas aeruginosa pathogenic isolates and molecular mechanism of action.

Biofilm formation of the opportunistic pathogen Pseudomonas (P). aeruginosa is one of the major global challenges to control nosocomial infections due to their high resistance to antimicrobials and host defense mechanisms. The present study aimed to assess the antibacterial and the antibiofilm activities of Peganum (P). harmala seed extract against multidrug-resistant P. aeruginosa isolates. Chemical identification of the active compound and determination of its molecular mechanism of action were also investigated. Results showed that P. harmala n-butanol "n-BuOH" extract exhibited antibacterial activity against multidrug-resistant P. aeruginosa isolates. This extract was even more active than conventional antibiotics cefazolin and vaamox when tested against three P. aeruginosa multidrug-resistant isolates. In addition, P. harmala n-BuOH extract exhibited potent bactericidal activity against PAO1 strain at MIC value corresponding to 500 µg/mL and attained 100% killing effect at 24 h of incubation. Furthermore, P. harmala n-BuOH extract showed an antibiofilm activity against P. aeruginosa PAO1 and exhibited 80.43% inhibition at sub-inhibitory concentration. The extract also eradicated 83.99% of the biofilm-forming bacteria. The active compound was identified by gas chromatography-mass spectrometry as an indole alkaloid harmaline. Transcriptomic analysis showed complete inhibition of the biofilm-related gene pilA when PAO1 cells were treated with harmaline. Our results revealed that P. harmala seed extract and its active compound harmaline could be considered as a candidate for a new treatment of multidrug-resistant P. aeruginosa pathogens-associated biofilm infections.

Potential of Exopolysaccharide from Porphyridium marinum to Contend with Bacterial Proliferation, Biofilm Formation, and Breast Cancer.

Exopolysaccharide (EPS) from marine microalgae are promising sources of a new generation of drugs. However, lot of them remain to be discovered and tested. In this study, EPS produced by Porphyridium marinum and its oligomers prepared by High Pressure Homogenizer have been tested for different biological activities, i.e., antibacterial, anti-fungal and antibiofilm activities on Candida albicans, as well as for their effects on the viability of murine breast cancer cells. Results have shown that all EPS samples present some biological activity. For antibacterial and antibiofilm activities, the native EPS exhibited a better efficiency with Minimum Inhibitory Concentration (MIC) from 62.5 µg/mL to 1000 µg/mL depending on the bacterial strain. For Candida albicans, the biofilm formation was reduced by about 90% by using only a 31.3 µg/mL concentration. Concerning breast cancer cells, lower molar masses fractions appeared to be more efficient, with a reduction of viability of up to 55%. Finally, analyses of polymers composition and viscosity measurements were conducted on all samples, in order to propose hypotheses involving the activities caused by the intrinsic properties of polymers.

Phytochemical investigation and biological activities of Echium arenarium (Guss) extracts.

The present work was developed to evaluate the in vitro antioxidant, antibacterial, antileishmanial and cytotoxic activities of Echium arenarium (Guss) extracts, and to analyze their phytochemical composition. The highest content of total phenolic compounds was obtained in the ethyl acetate extract which showed the best DPPH scavenging activity and ß-carotene bleaching inhibition (IC50 = 1.1 and 9.94 µg/mL respectively). It also exhibited the highest antibacterial activity against Gram-positive bacteria (L. monocytogenes; S. aureus; MRSA, E. faecalis and B. cereus) and antileishmanial activity against L. major (IC50 = 13.91 ±â€¯0.43 µg/mL) and L. infantum (IC50 = 9.91 ±â€¯0.15 µg/mL). Moreover, the active extract exhibited potent antiamastigote activity (IC50 = 22.48 ±â€¯0.14 µg/mL and 18.59 ±â€¯0.09 µg/mL against L. major and L. infantum respectively). Cytotoxicity studies revealed low toxicity against Raw 264.7 macrophage cell line (IC50 = 145.80 ±â€¯0.84 µg/mL, SI < 10). Luteolin-7-O-glucoside was identified as the major flavonoid component by RP-HPLC analysis. In conclusion, Echium arenarium (Guss) extract was characterized by a wide range of biological activities and could be used as a potential natural anti-infectious drug.

Streptomyces tunisialbus sp. nov., a novel Streptomyces species with antimicrobial activity.

A novel actinomycete strain designated S2T was isolated from Tunisian rhizosphere soil of Lavandula officinalis. This isolate exhibited broad spectrum antibacterial activity against several Gram-positive and Gram-negative bacteria and also antifungal activity against yeast and filamentous fungi. The isolate S2T presents morphological and chemotaxonomic characteristics typical of the members of the genus Streptomyces. Whole cell hydrolysates of S2T were found to contain LL-diaminopimelic acid. The major fatty acids were identified as C16:0, anteiso-C15:0 and iso-C16:0 whereas the predominant menaquinones were found to be MK-9(H6) and MK-9(H8). The polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside and three unidentified compounds. The G+C content of the genomic DNA was determined to be 71.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S2T belongs to the genus Streptomyces and is closely related to Streptomyces netropsis DSM 40259T with 99.86% sequence similarity. Multi-locus sequence analysis (MLSA) based on four house-keeping gene alleles (gyrB, recA, trpB, rpoB) showed that isolate S2T is closely related to S. netropsis, with an MLSA distance greater than 0.007. The DNA-DNA relatedness between strain S2T and its near phylogenetic neighbour was 63.6 ± 2.3%, which is lower than the 70% threshold value for delineation of genomic prokaryotic species. This isolate was also distinguished from the type strain S. netropsis DSM 40259T, using a combination of morphological and physiological features. Based on its phenotypic and molecular properties, strain S2T is considered to represent a novel species of the genus Streptomyces, for which the name Streptomyces tunisialbus sp. nov. is proposed. The type strain is S2T (= JCM 32165T = DSM 105760T).

Hyporientalin A, an anti-Candida peptaibol from a marine Trichoderma orientale.

A Trichoderma orientale strain LSBA1 was isolated from the Mediterranean marine sponge Cymbaxinella damicornis. The crude extract of T. orientale mycelium showed inhibitory activity against growth of Gram-positive and Gram-negative bacteria as well as clinical isolates of Candida albicans. Purification of the anti-Candida component was performed using a combination of open silica gel-60 column and reverse phase high performance liquid chromatography. The active compound called hyporientalin A has been identified as a peptaibol analogue of longibrachin-A-II using mass spectrometry. It exhibited fungicidal activity against clinical isolates of C. albicans with minimal inhibitory concentrations (MICs) ranging from 2.49 to 19.66 µM, comparable to that of the antifungal agent amphotericin B. Our data support the use of hyporientalin A as a promising new and efficient antifungal drug in the treatment of candidiasis while controlling toxicity.

Antifungal mechanism of the combination of Cinnamomum verum and Pelargonium graveolens essential oils with fluconazole against pathogenic Candida strains.

The present study aimed to investigate the anti-Candida activity of ten essential oils (EOs) and to evaluate their potential synergism with conventional drugs. The effect on secreted aspartic protease (SAP) activity and the mechanism of action were also explored. The antifungal properties of essential oils were investigated using standard micro-broth dilution assay. Only Cinnamomum verum, Thymus capitatus, Syzygium aromaticum, and Pelargonium graveolens exhibited a broad spectrum of activity against a variety of pathogenic Candida strains. Chemical composition of active essential oils was performed by gas chromatography-mass spectrometry (GC-MS). Synergistic effect was observed with the combinations C. verum/fluconazole and P. graveolens/fluconazole, with FIC value 0.37. Investigation of the mechanism of action revealed that C. verum EO reduced the quantity of ergosterol to 83%. A total inhibition was observed for the combination C. verum/fluconazole. However, P. graveolens EO may disturb the permeability barrier of the fungal cell wall. An increase of MIC values of P. graveolens EO and the combination with fluconazole was observed with osmoprotectants (sorbitol and PEG6000). Furthermore, the combination with fluconazole may affect ergosterol biosynthesis and disturb fatty acid homeostasis in C. albicans cells as the quantity of ergosterol and oleic acid was reduced to 52.33 and 72%, respectively. The combination of P. graveolens and C. verum EOs with fluconazole inhibited 78.31 and 64.72% SAP activity, respectively. To our knowledge, this is the first report underlying the mechanism of action and the inhibitory effect of SAP activity of essential oils in synergy with fluconazole. Naturally occurring phytochemicals C. verum and P. graveolens could be effective candidate to enhance the efficacy of fluconazole-based therapy of C. albicans infections.

Synergistic fungicidal activity of the lipopeptide bacillomycin D with amphotericin B against pathogenic Candida species.

In the present study, the synergism of the lipopeptide bacillomycin D in combination with the polyene amphotericin B against pathogenic Candida species is described along with their potential cytotoxicity against mammalian cells. Bacillomycin D inhibited the growth of various Candida species at minimal concentrations from 12.5 to 25 µg ml(-1). Furthermore, it showed a synergistic effect with the antifungal drug amphotericin B in inhibiting the growth of Candida strains, with fractional inhibitory concentration indices ranging from 0.28 to 0.5. Time killing studies revealed a >2-log reduction in the viability of Candida albicans ATCC 10231 cells after 3 h incubation with the combination amphotericin B plus bacillomycin D, at their subinhibitory concentration. Interestingly, when the two drugs were used together at those dosages displaying a synergism in the anti-Candida activity, no cytotoxic effect was observed against mammalian cells. Therefore, the combination bacillomycin D/amphotericin B may represent a valid alternative to conventional antifungals for topical treatment of C. albicans infections. To the best of our knowledge, this is the first report describing the in vitro interaction between the antifungal drug amphotericin B and bacillomycin D against pathogenic Candida species.

Effect of Lipopeptide-Loaded Chitosan Nanoparticles on Candida albicans Adhesion and on the Growth of Leishmania major.

Cyclic lipopeptides produced by Bacillus species exhibit interesting therapeutic potential. However, their clinical use remains limited due to their low stability, undesirable interactions with host macromolecules, and their potential toxicity to mammalian cells. The present work aims to develop suitable lipopeptide-loaded chitosan nanoparticles with improved biological properties and reduced toxicity. Surfactin and bacillomycin D lipopeptides produced by Bacillus amyloliquefaciens B84 strain were loaded onto chitosan nanoparticles by ionotropic gelation process. Nanoformulated lipopeptides exhibit an average size of 569 nm, a zeta potential range of 38.8 mV, and encapsulation efficiency (EE) of 85.58%. Treatment of Candida (C.) albicans cells with encapsulated lipopeptides induced anti-adhesive activity of 81.17% and decreased cell surface hydrophobicity (CSH) by 25.53% at 2000 µg/mL. Nanoformulated lipopeptides also induced antileishmanial activity against Leishmania (L.) major promastigote and amastigote forms at respective IC50 values of 14.37 µg/mL and 22.45 µg/mL. Nanoencapsulated lipopeptides exerted low cytotoxicity towards human erythrocytes and Raw 264.7 macrophage cell line with respective HC50 and LC50 values of 770 µg/mL and 234.56 µg/mL. Nanoencapsulated lipopeptides could be used as a potential delivery system of lipopeptides to improve their anti-adhesive effect against C. albicans cells colonizing medical devices and their anti-infectious activity against leishmania.

Utilization of Grape Seed Flour for Antimicrobial Lipopeptide Production by Bacillus amyloliquefaciens C5 Strain.

An endophytic Bacillus amyloliquefaciens strain called C5, able to produce biosurfactant lipopeptides with a broad antibacterial activity spectrum, has been isolated from the roots of olive tree. Optimization of antibacterial activity was undertaken using grape seed flour (GSF) substrate at 0.02, 0.2, and 2% (w/v) in M9 medium. Strain C5 exhibited optimal growth and antimicrobial activity (MIC value of 60 µg/ml) when incubated in the presence of 0.2% GSF while lipopeptide production culminated at 2% GSF. Thin layer chromatography analysis of lipopeptide extract revealed the presence of at least three active spots at Rf 0.35, 0.59, and 0.72 at 0.2% GSF. Data were similar to those obtained in LB-rich medium. MALDI-TOF/MS analysis of lipopeptide extract obtained from 0.2% GSF substrate revealed the presence of surfactin and bacillomycin D. These results show that GSF could be used as a low-cost culture medium supplement for optimizing the production of biosurfactants by strain C5.

Biological control of the soft rot bacterium Pectobacterium carotovorum by Bacillus amyloliquefaciens strain Ar10 producing glycolipid-like compounds.

Four hundred and fifty bacteria were evaluated for antagonistic activity against bacterial soft rot of potato caused by Pectobacterium carotovorum sp strain II16. A strain Ar10 exhibiting potent antagonist activity has been identified as Bacillus amyloliquefaciens on the basis of biochemical and molecular characterization. Cell free supernatant showed a broad spectrum of antibacterial activity against human and phytopathogenic bacteria in the range of 10-60 AU/mL. Incubation of P. carotovorum cells with increasing concentrations of the antibacterial compound showed a killing rate of 94.8 and 96% at MIC and 2xMIC respectively. In addition, the antibacterial agent did not exert haemolytic activity at the active concentration and has been preliminary characterized by TLC and GC-MS as a glycolipid compound. Treatment of potato tubers with strain Ar10 for 72 h significantly reduced the severity of disease symptoms (100 and 85.05% reduction of necrosis deep / area and weight loss respectively). The same levels in disease symptoms severity was also recorded following treatment of potato tubers with cell free supernatant for 1 h. Data suggest that protection against potato soft rot disease may be related to glycolipid production by strain Ar10. The present study affords new alternatives for anti-Pectobacterium carotovorum bioactive compounds against the soft rot disease of potato.

Enhancement of Exochitinase Production by Bacillus licheniformis AT6 Strain and Improvement of N-Acetylglucosamine Production.

A strain producing chitinase, isolated from potato stem tissue, was identified as Bacillus licheniformis by biochemical properties and 16S RNA sequence analysis. Statistical experimental designs were used to optimize nine independent variables for chitinase production by B. licheniformis AT6 strain in submerged fermentation. Using Plackett-Burman design, (NH4)2SO4, MgSO4.7H2O, colloidal chitin, MnCl2 2H2O, and temperature were found to influence chitinase production significantly. According to Box-Behnken response surface methodology, the optimal fermentation conditions allowing maximum chitinase production were (in gram per liter): (NH4)2SO4, 7; K2HPO4, 1; NaCl, 1; MgSO4.7H2O, 0.1; yeast extract, 0.5; colloidal chitin, 7.5; MnCl2.2H2O, 0.2; temperature 35 °C; pH medium 7. The optimization strategy led to a 10-fold increase in chitinase activity (505.26 ± 22.223 mU/mL versus 50.35 ± 19.62 mU/mL for control basal medium). A major protein band with a molecular weight of 61.9 kDa corresponding to chitinase activity was clearly detected under optimized conditions. Chitinase activity produced in optimized medium mainly releases N-acetyl glucosamine (GlcNAc) monomer from colloidal chitin. This enzyme also acts as an exochitinase with ß-N-acetylglucosaminidase. These results suggest that B. licheniformis AT6 secreting exochitinase is highly efficient in GlcNAc production which could in turn be envisaged as a therapeutic agent or as a conservator against the alteration of several ailments.

Isolation of a chitinolytic Bacillus licheniformis S213 strain exerting a biological control against Phoma medicaginis infection.

Among nine chitinase-producing strains isolated from Tunisian soil, one isolate called S213 exhibited a potent chitinolytic activity. S213 strain was identified as Bacillus licheniformis by API 50CH system and sequence analysis of its partial 16S ribosomal DNA. Chitinolytic activity was induced either by colloidal chitin or fungal cell walls, and the highest chitinase activity reached at the late stationary phase exhibiting optimal temperature and pH of 50-60 °C and pH 6.0, respectively. SDS-PAGE analysis of the secreted colloidal chitin-induced proteins showed a major protein of about 65 kDa. This protein was identified as chitinase on the basis of its peptide sequences which displayed high homology with chitinase sequence of B. licheniformis ATCC 14580. Moreover, chitinolytic activity containing supernatant inhibited the growth of several phytopathogenic fungi including Phoma medicaginis. Interestingly, S213 strain reduced efficiently the damping-off disease caused by P. medicaginis in Medicago truncatula and should be envisaged in enzyme-based biopesticides against phytopathogen application.

Cyclo-(His,Leu): a new microbial diketopiperazine from a terrestrial Bacillus subtilis strain B38.

In continuation of our search for bioactive secondary metabolites from terrestrial Bacillus spp., a new microbial diketopiperazine, cis-cyclo-(His,Leu) (1) was isolated from the ethyl acetate extract of a strain B. subtilis B38, together with cis-cyclo-(Phe,Phe) (2), tryptophane (3), cis-cyclo-(Leu,Tyr) (4), cis-cyclo-(Trp,Tyr) (5) and macrolactin A (6). The chemical structures of the isolated compounds were identified by comparison of their 1D, 2D NMR and HRESIMS data with authentic spectra and literatures. To the best of our knowledge, this is the first time that cyclo-(His,Leu) has been isolated from natural products.

Antioxidative and DNA protective effects of bacillomycin D-like lipopeptides produced by b38 strain.

In the present study, we evaluated the antioxidant and the scavenging ability of C14, C15 and C16 bacillomycin D-like lipopeptides produced by B38 strain. They all displayed strong reducing power activity, hydroxyl and superoxide anion radicals scavenging activities and inhibition of lipid peroxidation. In addition, they were found to protect plasmid DNA damage from hydroxyl radical oxidation. Data suggested that their antioxidant potency can be attributed to the hydrophobic and aromatic side-chain groups of their amino acids as well as to the aliphatic chain of their beta amino fatty acids. Note that the hydrocarbon chain length did not interfere with the antioxidant power. Overall, such bacillomycin D lipopeptides which exhibit antioxidant and radical scavenging activities may be useful for cosmetic, therapeutic or pharmaceutical purposes in order to delay or prevent oxidative deterioration of manufactured products.