Fungicidal activity of the human peptide hepcidin 20 alone or in combination with other antifungals against Candida glabrata isolates

Candida glabrata infections are often difficult to eradicate due to the intrinsically low susceptibility to azoles of this species. In addition, C. glabrata has also been shown to be insensitive to several cationic peptides, which have been shown to be promising novel therapeutic candidates for the treatment of fungal infection. In this study, the in vitro fungicidal activity of the human cationic peptide hepcidin 20 (Hep-20) was evaluated against clinical isolates of C. glabrata with different levels of fluconazole susceptibility. Interestingly, all isolates were susceptible to Hep-20 (100–200 μg/ml) at pH 7.4, whereas the fungicidal effect of the peptide was higher (50 μg/ml) at acidic pH values. In addition, an increased antifungal activity was observed for Hep-20 with amphotericin B and a synergistic effect was demonstrated for the Hep-20/fluconazole and Hep-20/caspofungin combinations.     

Potential-dependent permeabilization of plasma membrane by the peptide BTM-P1 derived from the Cry11Bb1 protoxin

The peptide BTM-P1, which is derived from the amino acid sequence of the Cry11Bb1 protoxin, is able to permeabilize mitochondrial membranes and reveals antimicrobial activity. In this work we demonstrated that the permeabilizing activity of BTM-P1 for the plasma membrane of rat red blood cells increased in a dose-dependent manner for the concentration range of 1-4 μg/ml. Using osmotic protectants, the radius of pores formed at 4 μg/ml BTM-P1 was determined as 0.8 nm for 5 min hemolysis data, 0.7 nm for 5 min decrease in light dispersion of the cell suspension and 0.5 nm for the light dispersion slope measurements. The permeabilizing activity of 1 μg/ml peptide was increased by valinomycin-induced plasma membrane potential, especially under moderately hypotonic conditions. These results might explain the antimicrobial activity of BTM-P1 and support the hypothesis of potential-dependent and pro-apoptotic character of toxicity of naturally proteolysed Cry11Bb1 protoxin for epithelial cells of mosquito larvae midgut.     

Tertiary structure-related activity of tick defensin (persulcatusin) in the taiga tick, <Emphasis Type="Italic">Ixodes persulcatus</Emphasis>

Defensins are small cysteine-rich cationic proteins found in both vertebrates and invertebrates constituting the front line of host innate immunity. To examine the importance of the tertiary structure of tick defensin in its antimicrobial activity, we synthesized two types of the peptides with tertiary structure or primary one on basis of the information of the sequence in the defensin originated from the taiga tick, Ixodes persulcatus. Chemically synthesized peptides were used to investigate the activity spectrum against Staphylococcus aureus, Borrelia garinii and flora-associated bacteria. Both synthetic peptides showed antimicrobial activity against S. aureus in short-time killing within 1 h, but they do not show the activity against B. garinii, Stenotrophomonas maltophila and Bacillus spp., which were frequently isolated from the midgut of I. persulcatus. The teriary structure brought more potent activity to S. aureus than primary one in short-time killing. We also examined its antimicrobial activity by evaluation of growth inhibition in the presence of the synthetic peptides. Minimum inhibitory concentration (MIC) was ranged from 1.2 to 5.0 μg/ml in tertiary peptide and from 10 to 40 μg/ml in primary peptide, when 10 strains of S. aureus were used. From the curve of cumulative inhibition rates, MIC50 (MIC which half of the strains showed) to S. aureus is about 1.2 μg/ml in the peptide with tertiary structure and about 10 μg/ml in the linear one. Corynebacterium renale is 10 times or more sensitive to tertiary peptide than primary one. In conclusion, the presence of 3 disulfide bridges, which stabilize the molecule and maintain the tertiary structure, is considered to have an effect on their antimicrobial activities against Gram-positive bacteria such as S. aureus.     

2,2′-Dithienyl diselenide pro-oxidant activity accounts for antibacterial and antifungal activities

The aim of this study was to explore if 2,2′-dithienyl diselenide (DTDS) pro-oxidant activity is related to its antibacterial and antifungal actions. The antimicrobial activity of DTDS against bacterial and fungal was investigated in the broth microdilution assay (3.02–387 μg/ml). Additionally, the survival curve of microorganisms in the presence of DTDS (12.09–193.5 μg/ml) was performed. The involvement of pro-oxidant activity in the DTDS antimicrobial action was investigated by supplementing the growth medium with 10 mM glutathione or ascorbic acid in the disk diffusion technique (0.64–640 μg DTDS/discs). The levels of reactive species (RS) induced by 25 mM DTDS were also determined. The results demonstrated that DTDS was effective in preventing the Gram-positive bacteria and Candida albicans growth. The minimum inhibitory concentration, twice and half concentrations of DTDS confirmed that the activity of compound was bactericidal for some microorganisms (Enterococcus faecalis, and Staphylococcus saprophyticus), bacteriostatic for Bacillus cereus and fungistatic for C. albicans. Antibacterial and antifungal actions of DTDS are related to the increase of reactive species levels. The presence of antioxidants in the growth medium avoided the DTDS antimicrobial action. In conclusion, DTDS showed promising antibacterial and antifungal actions, possibly related to its pro-oxidant activity.     

Isolation and Chemical Characterization of an Alpha-Helical Peptide,Dendrocin-ZM1, Derived from Zataria multiflora Boiss with Potent Antibacterial Activity

Today, resistance of microorganisms to antibiotics has become a major challenge. To overcome this problem, development of new drugs, besides research on their antibacterial activity, is essential. Among chemical components, antimicrobial peptides (AMPs) exhibit antibacterial activity and can be selected as suitable antimicrobial candidates. In this study, a novel antimicrobial peptide, called dendrocin-ZM1, with a molecular weight of?~3716.48 Da, was isolated from Zataria multiflora Boiss (ZM) and purified via precipitation with ammonium sulfate and reverse-phase HPLC chromatography; it was then sequenced via Edman degradation. The in silico method was used to examine the physicochemical properties of dendrocin-ZM1. In this study, four reference strains (gram-positive and gram-negative) and one clinical vancomycin-resistant Staphylococcus aureus strain were used to survey the antimicrobial activities. Moreover, to examine cytotoxicity and hemolytic activity, a HEK-293 cell line and human red blood cells (RBCs) were used, respectively. Evaluation of the physicochemical properties of dendrocin-ZM1, as an AMP, indicated a net charge of?+?7 and a hydrophobicity percentage of 54%. This peptide had an amphipathic alpha-helical conformation. It exhibited broad-spectrum antibacterial activities against the tested strains at minimum inhibitory concentrations (MICs) of 4–16 μg/mL. Besides, this peptide showed negligible hemolysis and cytotoxicity in the MIC range. It also exhibited heat stability at temperatures of 20 to 80 °C and was active in a broad pH range (from 6.0 to 10.0). Overall, the present results suggested dendrocin-ZM1 as a remarkable antimicrobial candidate.

     

Analysis of antimicrobial peptides from porcine neutrophils

Cationic host defence peptides are important components of innate immunity in pigs and other mammalians. Most of these peptides have a direct antimicrobial activity and they also have a broad spectrum of effects on the host immune system, which may be taken into account in the introduction of novel therapeutics. Our method permits simultaneous isolation of six antibacterial peptides, i.e. prophenin-1, prophenin-2, PR-39, and protegrins 1-3 from a porcine neutrophil crude extract and characterisation of them. Among the obtained peptides the greatest bactericidal activity expressed as MBC was seen in protegrins (10 μg/ml), whereas in the other studied peptides MBC was on the level of 20 μg/ml. Minimal inhibitory concentrations (MIC) reached 10 μg/ml for protegrins 1-3 and 20 μg/ml for prophenins, and PR-39. Within the bactericidal range all isolated peptides didn't show cytotoxicity on cell lines used in our experiment.     

A novel cysteine-rich antimicrobial peptide from the mucus of the snail of Achatina fulica

Antimicrobial peptides (AMPs) are important components of the innate immunity. Many antimicrobial peptides have been found from marine mollusks. Little information about AMPs of mollusks living on land is available. A novel cysteine-rich antimicrobial peptide (mytimacin-AF) belonging to the peptide family of mytimacins was purified and characterized from the mucus of the snail of Achatina fulica. Its cDNA was also cloned from the cDNA library. Mytimacin-AF is composed of 80 amino acid residues including 10 cysteines. Mytimacin-AF showed potent antimicrobial activity against Gram-negative and Gram-positive bacteria and the fungus Candida albicans. Among tested microorganisms, it exerted strongest antimicrobial activity against Staphylococcus aureus with a minimal peptide concentration (MIC) of 1.9 μg/ml. Mytimacin-AF had little hemolytic activity against human blood red cells. The current work confirmed the presence of mytimacin-like antimicrobial peptide in land-living mollusks.     

StCT2, a new antibacterial peptide characterized from the venom of the scorpion Scorpiops tibetanus

Bacterial infection poses an increasing threat to global public health and new types of antibacterial agents are urgently needed to respond to the threat. Scorpion venom contains series of bioactive peptides, among which antibacterial peptide is an important part. Herein, a new antimicrobial peptide StCT2 was characterized from the venomous gland cDNA library of the Scorpiops tibetanus. The full-length cDNA of StCT2 is 369 nucleotides encoding the precursor that contains a putative 24 residues signal peptide, a presumed 14 residues mature peptide, and a putative 37 residues acidic propeptide at the C-terminus. The minimal inhibition concentrations (MICs) of StCT2 for Staphylococcus aureus were 6.25-25μg/ml, including antibiotic-resistant strains such as methicillin resistant S. aureus (MRSA). StCT2 was further found to show high in vivo antimicrobial activity by an S. aureus infection mouse model. StCT2 exerted its antimicrobial activity via a rapid bactericidal mechanism. Taken together, these results demonstrate the efficacy and general mechanism of StCT2 antimicrobial action and the therapeutic potential of StCT2 as a new antimicrobial peptide.     

Design and Synthesis of Lipopolysaccharide-Binding Antimicrobial Peptides Based on Truncated Rabbit and Human CAP18 Peptides and Evaluation of Their Action Mechanism

Lipopolysaccharide (LPS) is a toxic and immunogenic agent for human. Additionally, LPS is a good target for some antimicrobial compounds, including antimicrobial peptides (AMPs). LPS-binding peptides (LBPs) can recognize and neutralize LPS. Rabbit and human cathelicidins are AMPs with LPS-binding activity. In this study, we designed and synthesized two new truncated LBPs from rabbit and human CAP18 peptides by in silico methods. After synthesis of peptides, the antimicrobial properties and LPS-binding activity of these peptides were evaluated. The parental rabbit and human CAP18 peptides were selected as positive controls. Next, the changes in the secondary structure of these peptides before and after treatment with LPS were measured by circular dichroism (CD). Human cytotoxicity of the peptides was evaluated by MTT and red blood cells (RBCs) hemolysis assays. Finally, field emission scanning electron microscopy (FE-SEM), confocal microscopy, and flow cytometry were performed to study the action mechanism of these peptides. Results indicated that the hCap18 and rCap18 had antibacterial activity (at a MIC of 4–128 μg/mL). The results of the quantitative LAL test demonstrated that LPS-binding activity of hCap18 peptide was better than rCap18, while rCap18 peptide had better antimicrobial properties. Furthermore, rCap18 had less cytotoxicity than hCap18. However, both peptides were nontoxic for normal human skin fibroblast cell in MIC range. In conclusion, rCap18 has good antibacterial properties, while hCap18 can be tested as a diagnostic molecule in our future studies.

     

Antimicrobial potential of Indian Cinnamomum species

Cinnamomum is the largest genus of Lauraceae family and has been used as spices, food, and food additives by the people. Total 15 Cinnamomum species are distributed in different parts of Indian sub-continent. Different parts (leaves, stem bark, stem wood, roots, flowers, and fruits) of these species were shade-dried and used for the determination of essential oils. A total of 19 essential oils were identified and quantified from the different parts of (leaf, stem bark, stem wood, root, flower, and fruit) of 15 Cinnamomum species. The stem bark of C. altissimum was rich in the presence of essential oils (52.2 %) whereas minimum levels of essential oils were recorded in roots (17.9 %). The γ-terpinene (11.1 %) was reported as the major component essential oil in C. subavenium flowers. Methanol extract of C. camphora stem wood showed stronger lowest minimum inhibitory concentration against S. aureus (25 ± 0.01 μg/ml), H. pylori (29 ± 0.05 μg/ml), B. subtilis (31 ± 0.03 μg/ml), E. faecalis (33 ± 0.01 μg/ml), C. albicans (38 ± 0.03 μg/ml) when compared to amoxycillin (S. aureus 56 ± 0.05 μg/ml; B. subtilis 27 ± 0.04 μg/ml, E. faecalis 22 ± 0.01 μg/ml), streptomycin (H. pylori 38 ± 0.02 μg/ml) and fluconazole (C. albicans 56 ± 0.01 μg/ml). Methanolic extract of C. camphora stem wood demonstrated maximum antimicrobial activity against S. aureus, H. pylori, B. subtilis, E. faecalis and C. albicans. The essential oil of C. altissimum stem bark displayed significant lowest MIC against S. aureus (21 ± 0.03 μg/ml), E. coli (22 ± 0.03 μg/ml), E. cloacae (37 ± 0.06 μg/ml), L. monocytogenes (47 ± 0.08 μg/ml), and P. chrysogenum (101 ± 0.07 μg/ml) when compared to amoxycillin (E. coli 18 ± 0.01 μg/ml, E. cloacae 21 ± 0.05 μg/ml, L. monocytogenes 31 ± 0.03 μg/ml), and fluconazole (P. chrysogenum 101 ± 0.07 μg/ml). The essential oil of C. altissimum stem bark displayed maximum antimicrobial activity against S. aureus, E. coli, E. cloacae, L. monocytogenes, and P. chrysogenum. Cinnamomum essential oils may be used as an alternative source of antibacterial and antifungal compounds in the treatment of various types of infections.     

Antimicrobial peptides containing unnatural amino acid exhibit potent bactericidal activity against ESKAPE pathogens

A series of 36 synthetic antimicrobial peptides containing unnatural amino acids were screened to determine their effectiveness to treat Enterococcus faecium, Staphylococcus aureus, Klebsiella pnemoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species (ESKAPE) pathogens, which are known to commonly infect chronic wounds. The primary amino acid sequences of these peptides incorporate either three or six dipeptide units consisting of the unnatural amino acids Tetrahydroisoquinolinecarboxylic acid (Tic) and Octahydroindolecarboxylic acid (Oic). The Tic-Oic dipeptide units are separated by SPACER amino acids with specific physicochemical properties that control how these peptides interact with bacterial cell membranes of different chemical compositions. These peptides exhibited minimum inhibitory concentrations (MIC) against these pathogens in the range from >100 to 6.25 μg/mL. The observed diversity of MIC values for these peptides against the various bacterial strains are consistent with our hypothesis that the complementarity of the physicochemical properties of the peptide and the lipid of the bacteria’s cell membrane determines the resulting antibacterial activity of the peptide.     

Investigation of the Cytotoxicity of Antimicrobial Peptide P40 on Eukaryotic Cells

The in vitro cytotoxicity of the antimicrobial peptide P40 was investigated. The food grade bacteriocin nisin was also analyzed for comparison. VERO cells were treated with different concentrations (0.02–2.5 μg ml⁻¹) of nisin and P40, and cell viability and plasma membrane integrity were checked by MTT, neutral red uptake (NRU), and lactate dehydrogenase (LDH) assays. In MTT and NRU assays the EC₅₀ to the purified peptide P40 were 0.30 and 0.51 μg ml⁻¹, while values found to nisin were 0.35 and 0.79 μg ml⁻¹, respectively. In the LDH assay, the EC₅₀ was 0.57 and 0.62 μg ml⁻¹ for P40 and nisin, respectively. The peptide P40 revealed higher hemolytical activity (19%) when compared to nisin (4.9%) at the highest concentration tested (2.5 μg ml⁻¹). Relatively few studies about the cytotoxicity of antimicrobial peptides are available. The determination of the cytotoxicity of antimicrobial peptides is an essential step to warrant their safe use.     

Two peptides,TsAP-1 and TsAP-2, from the venom of the Brazilian yellow scorpion, Tityus serrulatus: Evaluation of their antimicrobial and anticancer activities

Here we report two novel 17-mer amidated linear peptides (TsAP-1 and TsAP-2) whose structures were deduced from cDNAs cloned from a venom-derived cDNA library of the Brazilian yellow scorpion, Tityus serrulatus. Both mature peptides were structurally-characterised following their location in chromatographic fractions of venom and synthetic replicates of each were subjected to a range of biological assays. The peptides were each active against model test micro-organisms but with different potencies. TsAP-1 was of low potency against all three test organisms (MICs 120–160 μM), whereas TsAP-2 was of high potency against the Gram-positive bacterium, Staphylococcus aureus (MIC 5 μM) and the yeast, Candida albicans (10 μM). Haemolytic activity of TsAP-1 was low (4% at 160 μM) and in contrast, that of TsAP-2 was considerably higher (18% at 20 μM). Substitution of four neutral amino acid residues with Lys residues in each peptide had dramatic effects on their antimicrobial potencies and haemolytic activities, particularly those of TsAP-1. The MICs of the enhanced cationic analogue (TsAP-S1) were 2.5 μM for S. aureus/C. albicans and 5 μM for E. coli but with an associated large increase in haemolytic activity (30% at 5 μM). The same Lys residue substitutions in TsAP-2 produced a dramatic effect on its MIC for E. coli lowering this from >320 μM to 5 μM. TsAP-1 was ineffective against three of the five human cancer cell lines tested while TsAP-2 inhibited the growth of all five. Lys residue substitution of both peptides enhanced their potency against all five cell lines with TsAp-S2 being the most potent with IC₅₀ values ranging between 0.83 and 2.0 μM. TsAP-1 and TsAP-2 are novel scorpion venom peptides with broad spectrum antimicrobial and anticancer cell activities the potencies of which can be significantly enhanced by increasing their cationicity.     

In-Silico and In-Vitro Evaluation of Antibacterial,Cytotoxic, and Apoptotic Activity and Structure of Modified CM11 Peptide

Drug-resistant infectious diseases have increased in recent years. Accordingly, plenty of researches are exploring novel approaches to overcome this problem. In this era, antimicrobial peptides have been identified as potential antibacterial agents. The Modified CM11 (mCM11) was designed with the C-terminal amidation and substitution of lysine with arginine. The designed peptide was synthesized by the solid-phase method and Rink amide p-methyl-benzhydryl amine resin. The synthesized peptide was evaluated using Mass Spectrometry (MS), High-Performance Liquid Chromatography (HPLC), and Circular Dichroism (CD). Finally, the antibacterial, cytotoxic, and apoptotic effect of the mCM11 peptide was investigated. The new peptide indicated a beta-sheet structure with a molecular weight of 1527.50 D and purity of 96%. The peptide exerted a potent antimicrobial activity against gram-negative and positive bacteria. The minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) ranged from 16 to 64 µg/ml, and 16 to 128 µg/ml, respectively. The IC₅₀ of mCM11 was 16 µg/ml and its cytotoxicity in SH-SY5Y cell line revealed a dose-dependent manner. Also, apoptosis analysis of eukaryotic cells revealed a decline in late apoptosis and necrosis in comparison with untreated cells. The mCM11 indicated a considerable antibacterial effect against a wide range of pathogenic bacterial strains. Further, it did not represent any late apoptotic and necrosis impact on the eukaryotic cell line. All of these findings may confirm the potential role of this new peptide as an effective therapeutic agent.

     

Catesbeianin-1, a novel antimicrobial peptide isolated from the skin of <Emphasis Type="Italic">Lithobates catesbeianus</Emphasis> (American bullfrog)

Objectives

To identify and characterize a novel antimicrobial peptide, catesbeianin-1.

Results

Catesbeianin-1 is 25 amino acids long and is α-helical, cationic and amphipathic. It had antimicrobial activity against Gram-positive and Gram-negative bacteria. It was resistant against trypsin and pepsin. Catesbeianin-1 exhibited moderate hemolytic activity (approx 8%) at 100 μg/ml, and its HC₅₀ (50% hemolytic concentration) was 300 μg/ml. Its cytotoxicity was approx 10–20% at 100 μg/ml, and its CC₅₀ (50% cytotoxic concentration) was >100 μg/ml. The LD₅₀ of catesbeianin-1 in mice was 80 mg/kg. At 3.1 µg/ml, catesbeianin-1 significantly inhibited the growth of methicillin-resistant Staphylococcus aureus.

Conclusions

A new antimicrobial peptide from the skin of Lithobates catesbeianus (American bullfrog) may represent a template for the development of novel antimicrobial agents.

     

Antimicrobial and cytotoxic activities of the crude extracts of Dietes bicolor leaves,flowers and rhizomes

The crude extracts of Dietes bicolor leaves, flowers and rhizomes were subjected to comparative antimicrobial screening against two Gram-positive, two Gram-negative bacteria and four fungal strains using the agar well diffusion method. The minimum inhibitory concentrations (MIC) of the tested extracts were also determined. Furthermore, the cytotoxic activity was evaluated. D. bicolor extracts generally demonstrated notable broad spectrum antimicrobial activities (MIC values ≤ 500 μg/mL) against all tested pathogens. D. bicolor leaf extract showed potent broad spectrum antimicrobial activity with MIC values ranging between 0.24 and 31.25 μg/mL against all tested pathogens. Moreover, the flowers extract exhibited promising antimicrobial activities, displaying MIC values ranging between 1.95 and 125 μg/mL against the tested bacteria and fungi. However, the rhizomes extract showed moderate antimicrobial activity with MIC values ranging between 31.25 and 500 μg/mL. Despite the potent antimicrobial activity of D. bicolor extracts, they were ineffective as cytotoxic agents against nine tested cancer cell lines, displaying 50% inhibitory concentration (IC₅₀) values above 100 μg/mL. The reported potent antimicrobial activity along with the lack of measurable cytotoxic activity indicated that the antimicrobial activity of D. bicolor crude extracts is mediated through a mechanism other than cytotoxicity. These results suggest that D. bicolor can act as a potential source for natural antibacterial and antifungal agents with a good safety profile at a preliminary level.     

The human antimicrobial peptide LL-37 and its fragments possess both antimicrobial and antibiofilm activities against multidrug-resistant Acinetobacter baumannii

Acinetobacter baumannii infections are difficult to treat due to multidrug resistance. Biofilm formation by A. baumannii is an additional factor in its ability to resist antimicrobial therapy. The antibacterial and antibiofilm activities of the human antimicrobial peptide LL-37 and its fragments KS-30, KR-20 and KR-12 against clinical isolates of multidrug-resistant (MDR) A. baumannii were evaluated. The minimal inhibitory concentration (MIC) of LL-37 against MDR A. baumannii isolates ranged from 16 to 32 μg/mL. The MIC of KS-30 fragment varied from 8.0 to16 μg/mL and the KR-20 fragment MIC ranged from 16 to 64 μg/mL. LL-37 and KS-30 fragment exhibited 100% bactericidal activity against five A. baumannii strains, including four MDR clinical isolates, within 30 min at concentrations of 0.25–1 μg/mL. By 0.5 h, the fragments KR-20 and KR-12 eliminated all tested strains at 8 and 64 μg/mL respectively. LL-37 and its fragments displayed anti-adherence activities between 32-128 μg/mL. A minimum biofilm eradication concentration (MBEC) biofilm assay demonstrated that LL-37 inhibited and dispersed A. baumannii biofilms at 32 μg/mL respectively. Truncated fragments of LL-37 inhibited biofilms at concentrations of 64–128 μg/mL. KS-30, the truncated variant of LL-37, effectively dispersed biofilms at 64 μg/mL. At 24 h, no detectable toxicity was observed at the efficacious doses when cytotoxicity assays were performed. Thus, LL-37, KS-30 and KR-20 exhibit significant antimicrobial activity against MDR A. baumannii. The prevention of biofilm formation in vitro by LL-37, KS-30 and KR-20 adds significance to their efficacy. These peptides can be potential therapeutics against MDR A. baumannii infections.     

De-Novo Design of Antimicrobial Peptides for Plant Protection

This work describes the de-novo design of peptides that inhibit a broad range of plant pathogens. Four structurally different groups of peptides were developed that differ in size and position of their charged and hydrophobic clusters and were assayed for their ability to inhibit bacterial growth and fungal spore germination. Several peptides are highly active at concentrations between 0,1 and 1 µg/ml against plant pathogenic bacteria, such as Pseudomonas syringae, Pectobacterium carotovorum, and Xanthomonas vesicatoria. Importantly, no hemolytic activity could be detected for these peptides at concentrations up to 200 µg/ml. Moreover, the peptides are also active after spraying on the plant surface demonstrating a possible way of application. In sum, our designed peptides represent new antimicrobial agents and with the increasing demand for antimicrobial compounds for production of “healthy” food, these peptides might serve as templates for novel antibacterial and antifungal agents.     

New antimicrobial anthraquinone 6,61-bis (1,5,7-trihydroxy-3-hydroxymethylanthraquinone) isolated from Streptomyces sp. isolate ERI-26

The present report is about Streptomyces sp. isolate ERI-26 isolated from the soil sample of Nilgiri forest, Western Ghats. The methanol extract of ERI-26 showed good antimicrobial activity against tested microbes. The antimicrobial novel anthraquinones were purified by bioactivity-guided fractionation using a silica gel column and preparative HPLC. The compound was characterized and identified by UV, IR, NMR and MASS spectral data. The compound named as 6,6¹-bis (1,5,7-trihydroxy-3-hydroxymethylanthraquinone), showed significant antimicrobial activities against tested microbes. The isolated compound inhibited the tested bacterial growth, Staphylococcus aureus at 62.5 μg/ml, Staphylococcus epidermidis at 15.62 μg/m, Bacillus subtilis at 62.5 μg/ml, fungi; Trichophyton mentagrophytes at 15.62 μg/m Trichophyton simii at 15.62 μg/ml, Aspergillus niger at. 7.81 μg/ml, Aspergiller flavus at 3.90 μg/ml, Trichophyton rubrum 296 at 62.5 μg/ml, T. rubrum 57/01 at 7.81 μg/ml, Magnaporthe grisea at 15.62 μg/ml. and Botrytis cinerea at 3.90 μg/ml. Isolated anthraquinone compound and its antimicrobial activity were newly reported.