Antibacterial Secondary Metabolites Research Articles

Biophysical and biochemical characterization of active secondary metabolites from Aspergillus allahabadii

Fungal secondary metabolites are a diverse group of natural chemical products with physiological relevance. We aimed to identify bioactive secondary metabolites from Aspergillus allahabadii. We used “activity-guided fractionation” strategy for the isolation of secondary metabolites. Crude extracts showed good antibacterial activity. Two antibacterial secondary metabolites have been isolated from the crude extract. Chemical characterization of these compounds was performed using biophysical techniques (FT-IR, NMR, and mass spectrometry). Structural characterization confirmed these to be pyrone derivatives: 3-hydroxy 2-methyl 4-pyrone and 5-hydroxy-2-(hydroxymethyl)-4H-pyrone. These bioactive pyrone derivatives have been identified as maltol and kojic acid. From our initial observations, we infer that these pyrone derivatives have potent antimicrobial, antioxidant, antidiabetic, and mosquito larvicidal activities and no cytotoxicity. These compounds could have potential therapeutic and biomedical applications, but further mechanistic studies using animal models are very much necessary.

Synthesis of Anti-Acne Ointment of Ethanol Extract of White Plumeria Leaves (Plumeria Alba L.)

Acne is a chronic inflammatory skin disease pilosebaceous follicle, where the oil- producing glands are clogged and contaminated by bacteria. Propionibacterium acne is one of the bacteria that contributes to the pathogenesis of acne. Acne treatment was done by reducing the population of bacteria using an antibacterial. One of the plants that have antibacterial activity is white plumeria. The ethanol extract of white plumeria leaves contains antibacterial secondary metabolites, which are alkaloids and saponins. The aim of this study is to formulate white plumeria leaves extract into the water leached ointment base. Characteristics of the ointment were determined by evaluating the stability of the ointment including organoleptic, adhesion test, dispersive power test, determination of pH, and the antibacterial activity test. The results showed that the ointment of ethanol extract of white plumeria leaves has some characteristics, semisolid form, white, has distinctive smell of ointment, homogeneous but not protective, has a pH of 4.57 - 6.10, dispersive power of 5.10 - 6.06 cm, the adhesiveness of 1.67 - 3 seconds, and optimum antibacterial activity at concentrations of 5 ppm providing inhibition zone of 24.00 mm.

Anticancer and antibacterial secondary metabolites from the endophytic fungus Penicillium sp. CAM64 against multi-drug resistant Gram-negative bacteria.

The emergence of multiple-drug resistance bacteria has become a major threat and thus calls for an urgent need to search for new effective and safe anti-bacterial agents. This study aims to evaluate the anticancer and antibacterial activities of secondary metabolites from Penicillium sp., an endophytic fungus associated with leaves of Garcinia nobilis. The culture filtrate from the fermentation of Penicillium sp. was extracted and analyzed by liquid chromatography-mass spectrometry, and the major metabolites were isolated and identified by spectroscopic analyses and by comparison with published data. The antibacterial activity of the compounds was assessed by broth microdilution method while the anticancer activity was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The fractionation of the crude extract afforded penialidin A-C (1-3), citromycetin (4), p-hydroxyphenylglyoxalaldoxime (5) and brefelfin A (6). All of the compounds tested here showed antibacterial activity (MIC = 0.50 - 128 µg/mL) against Gramnegative multi-drug resistance bacteria, Vibrio cholerae (causative agent of dreadful disease cholera) and Shigella flexneri (causative agent of shigellosis), as well as the significant anticancer activity (LC50 = 0.88 - 9.21 µg/mL) against HeLa cells. The results obtained indicate that compounds 1-6 showed good antibacterial and anticancer activities with no toxicity to human red blood cells and normal Vero cells.

Study of Phytochemical Screening and Antimicrobial Activity of <i>Citrus aurantifolia</i> Seed Extracts

Citrus aurantifolia, the family Rutaceae, which consists of 150 genera and 900 species, is gaining grounds as important source for treatment in complementary medicine, and commonly called limone. Chloroform, methanol and ethanol extract exhibited significant antimicrobial activity and highlighted the biological monitoring of activity from the methanol extract of seeds. Phytochemical screening of the diethyl ether, methanol and aqueous extracts of seeds confirmed the presence of alkaloids, saponins, sterols and triterpenes, carotenoids, coumarins, tannins and carbohydrates. Chloroform extract was fractionated by sing liquid solid column chromatographic technique and column fractions eluted with chloroform and methanol. The antibacterial secondary metabolites were achieved by fractionation of the active. The seed extracts were monitored analytically by TLC preparative and some chemical analyses of seeds have been done such as determination of ash, nitrogen, protein content.

ISOLATION AND CHARACTERIZATION OF BIOTECHNOLOGY RELEVANT BACTERIA FROM MARINE ENVIRONMENT

Marine environment remained as largely unexplored source for researchers to discover marine microorganisms with novel properties. This study aims to isolate marine bacteria from the seashore of Desaru, Malaysia. Totally, six bacterial strains were successfully obtained and were identified by complete 16S rRNA sequencing. The characterizations of bacterial strains were performed based on morphological tests, Gram-staining, biochemical tests, and antibiotic sensitivity. The 16S rRNA sequence of D-2, D-4, D-7, D-15, D-31, and D-33 revealed a high identity of 97 to 99% with taxa belong to genera of Pseudomonas, Marinomonas, Exiquobacterium, Micrococcus, Pseudoalteromonas, and Shewanella respectively. Strain D-31 exhibited higher tolerance towards antibiotics kanamycin, ampicillin, and erythromycin while the growth of other strains were retarded by at least two of these antibiotics. We further characterized strain D-4 and D-31 that belonged to Marinomonas sp. and Pseudoalteromonas sp.. Both genera are interesting as earlier researchers have discovered new antibacterial substances, industrial enzymes and unique secondary metabolites.

Exploration of antibacterial metabolites producing marine bacteria from Sundarbans, Bangladesh

To combat the increasing numbers of antibiotic resistant strains of pathogenic bacteria new source of antibacterial agents are desperately needed. This study was aimed to discover new marine bacteria having antibacterial activity from marine soil samples of Sundarbans, Bangladesh. Using starch-casein-nitrate-agar medium thirty nine marine bacteria colonies were isolated as pure isolates from nine marine soil samples. Each of the isolates was preserved in both short term and long term basis. Based on the aerial and substrate mycelia color of the isolates they were grouped into five color series and were screened for their antibacterial activity against a series of test bacteria. Among thirty nine pure isolates twenty four isolates (61.5%) exhibited moderate to high activity against three grampositive and four gram-negative bacteria. This is due to the antibacterial metabolites secreted in the medium by most of the isolates. It suggested that Sundarbans may be an interesting, valuable and potential source for the exploration of novel marine bacteria with the potential to yield useful new antibacterial secondary metabolites of pharmaceutical interest.Bangladesh Pharmaceutical Journal 18(1): 53-60, 2015

Antibacterial secondary metabolites from an endophytic fungus, Eupenicillium sp. LG41.

Two new compounds containing the decalin moiety, eupenicinicols A and B (1 and 2), two new sirenin derivatives, eupenicisirenins A and B (3 and 4), and four known compounds, (2S)-butylitaconic acid (5), (2S)-hexylitaconic acid (6), xanthomegnin (7), and viridicatumtoxin (8), were isolated from an endophytic fungus, Eupenicillium sp. LG41, harbored in the roots of the Chinese medicinal plant Xanthium sibiricum. Their structures were confirmed through combined spectroscopic analysis (NMR and HRMS(n)), and their absolute configurations were deduced by ECD calculations or optical rotation data. Since the endophytic fungus was isolated from the roots, the antibacterial efficacies of the compounds 1-6 were investigated against Bacillus subtilis and Acinetobacter sp. BD4, which typically inhabit soil, as well as the clinically important Staphylococcus aureus and Escherichia coli. (2S)-Butylitaconic acid (5) and (2S)-hexylitaconic acid (6) exhibited pronounced efficacy against Acinetobacter sp., corroborating the notion that root-endophytes provide chemical defense to the host plants. Compound 2 was highly active against the clinically relevant S. aureus. By comparing 1 with 2, it was revealed that altering the substitution at C-11 could drastically increase the antibacterial efficacy of 1. Our study reveals plausible ecological roles of the endophyte and its potential pharmaceutical use as a source of antibacterial compounds.

Context dependency of infectious disease: the cyanobacterium Microcystis aeruginosa decreases white bacterial disease in Daphnia magna

Summary We investigate whether an increase in the occurrence of cyanobacterial blooms affects zooplankton–parasite interactions. Cyanobacteria are expected to be of poor food quality for zooplankton hosts and are therefore expected to increase parasitism. Nevertheless, simultaneous exposure to both stressors may lead to different results, given the antibacterial secondary metabolites of cyanobacteria. We exposed the zooplankter Daphnia magna to the cyanobacterial species Microcystis aeruginosa and the parasite that causes white bacterial disease in D. magna. Increased M. aeruginosa concentrations reduced the percentage of infected individuals and as such protected D. magna against parasitism. Interactions between M. aeruginosa and the parasite were antagonistic in terms of percentage of surviving Daphnia, total offspring per female and clutch size. Additional plating experiments showed a direct negative effect of Microcystis on bacterial growth. The results suggest that changes in phytoplankton affect host–parasite interactions in zooplankton. Contrary to the prevailing paradigm that multiple stressors often induce additive or synergistic effects, we report an antagonistic effect of the presence of cyanobacterial stress on parasites in Daphnia. Thus, assessment of the outcome of host–parasite interactions needs to incorporate the environmental context.

Antibacterial and antifungal activities of Actinobacteria isolated from Rathnagiri hills

Article history: Received on: 18/08/2012 Revised on: 29/08/2012 Accepted on: 05/09/2012 Available online: 29/10/2012 This study was performed to isolate actinomycete colonies having antibacterial and antifungal activity from soil samples. A total of 27 actinomycete colonies were isolated in pure culture from five soil samples using Starch casein agar medium. Entire isolates were screened for their antimicrobial activity by agar plug method against five each of human pathogenic bacteria and fungi. Of this, 7 strains inhibits B. substilis, 3 strains inhibits Klebseilla sp, 6 strains inhibits B. cerus, 5 strains inhibits S. aureus and only 2 strains inhibits E. coli. Incase of fungi all the actinobateria has moderate activity with less fungal strains, only 1 strain (RA 5) inhibits entire fungus except Penicillium sp. The metabolites from potent strain was produced by fermentation, separated by centrifugation, it was tested for their antimicrobial activity against the test bacterial and fungal strains by well diffusion and disc diffusion method. In this study, the metabolites from RA5 (identified as Streptomyces sp.) have showed good antibacterial and antifungal activity. Since many isolates showed inhibitory activity against indicator bacteria, it is suggestive that Rathnagiri hill’s soil could be an interesting source to explore for antibacterial secondary metabolites.

Antibacterial Secondary Metabolites from the Cave Sponge Xestospongia sp.

Chemical investigation of the cave sponge Xestospongia sp. resulted in the isolation of three new polyacetylenic long chain compounds along with two known metabolites. The structures of the new metabolites were established by NMR and MS analyses. The antibacterial activity of the new metabolites was also evaluated.

Antibacterial Activities of Actinomycete Isolates Collected from Soils of Rajshahi, Bangladesh

This study was performed to isolate actinomycete colonies having antibacterial activity from soil samples collected from different places around Rajshahi, Bangladesh. Thirty actinomycete colonies were isolated in pure culture from five soil samples using Starch-casein-nitrate-agar medium. The isolates were grouped in five color series based on their aerial mycelia color and screened for their antibacterial activity against a range of test bacteria. Sixteen isolates (53.3%) were found to have moderate to high activity against four gram-positive and four gram-negative bacteria. Since many isolates showed inhibitory activity against indicator bacteria, it is suggestive that Bangladeshi soil could be an interesting source to explore for antibacterial secondary metabolites.

Ocorrência e diversidade estrutural de metabólitos fúngicos com atividade antibiótica

Several reasons motivated the development of new generations of antibiotics, such as their high ability to develop resistance to virtually all kinds of anti-infective agents and the crescent market demand for new drugs to treat special demanding patients. After penicillin discovery, several antibiotics were developed from fungal metabolites, since antibacterial secondary metabolites consists on a fungal endogenous protective mechanism against natural competitors. The aim of this review is to present the structural diversity of antibacterial and antifungal metabolites produced by fungi, mentioning sources of fungal isolates, cultivation process and details on the scope of their antibiotic activity.

Actividad antibacteriana de extractos de hongos aislados de raíces del mangle Rhizophora mangle (Rhizophoraceae) en Venezuela

The antibacterial activity of marine fungi extracts was evaluated by a test of efficiency. The fungi were previously inoculated in Malt Agar (EMA) extract with 50% of seawater and growth for 60 days. Triplicate antibiograms were carried out with the extracts. An ANOVA I with a posteriori Duncan test were applied to the diameters of inhibition zones. The extracts of Aspergillus ochraceus 3MCMC3 and Penicillium citrinum (14) 4MCMC16 present wide spectral antibacterial properties, inhibiting 100% and 80% of the developing germs, especially Pseudomonas aeruginosa 9027. The extract of Penicillium (1) 3MLLC5 had the highest efficiency on this strain; P. aeruginosa 9027 and Escherichia coli 10536 were the most sensitive germs when treated with these extracts. These marine fungi can be an important source of antibacterial secondary metabolites.

Bacterial colonization of the phyllosphere of nineteen plant species and antimicrobial activity of their leaf secondary metabolites against leaf associated bacteria

The scope of this work was to examine whether leaf constitutive secondary metabolites play a role in determining bacterial colonization of the phyllosphere. To this aim, we surveyed nineteen native or cultivated plant species that share a common bacterial pool in a North Mediterranean area, and estimated the size of total and ice nucleation active (INA) bacterial populations on their leaves. Large differences in the colonization of their phyllosphere were found; the population size of epiphytic bacteria ranged from 7.5 × 102 to 1 × 106 CFU/g fresh weight, in eucalypt and celery, respectively. Species native in Mediterranean-type climate areas, particularly those belonging to the group of aromatic plants, are characterized by scarce presence of INA bacteria. The antibacterial activity of essential oils, surface phenolics and leaf tissue extracts was also estimated against the INA strains P. syringae and E. herbicola, isolated from two of these plant species. E. herbicola proved more sensitive than P. syringae. Of the species examined, oregano [Origanum vulgare L. subsp. hirtum (Link.) Ietswaart], an aromatic plant, had the highest antimicrobial activity, whereas six species showed no activity at all. Further experiments were performed with oregano and bean (Phaseolus vulgaris L.) that represent two extremes in their secondary metabolite content. Both plants were inoculated with P. syringae. By the end of incubation, the bacterial population on bean plants was about 100 times higher than that on oregano leaves. Scanning electron micrographs showed that bacterial growth on oregano leaves was confined to sites away from glandular hairs. Results from the bacterial colonization survey together with those from the toxicity tests showed that all species rich in antibacterial secondary metabolites harbored low leaf bacterial populations. These results provide substantial evidence that leaf secondary metabolites function as constitutive defense chemicals against microbial invasions. However, the fact that species with non- or moderately active leaf secondary metabolites are not always highly colonized suggests mediation of other unknown factors, the contribution of which requires further investigation.

Antimicrobial activity in sub-Arctic marine invertebrates

In the marine environment, any living or non-living surface is exposed to bacterial colonization. Many invertebrate species in temperate, tropical and Antarctic regions have demonstrated chemical defences against the formation of microbial films. In the present study, the antimicrobial activity of sub-Arctic invertebrates was investigated for the first time. Crude extracts of abundant invertebrates belonging to several taxonomic groups were tested for their inhibitory effects on the growth of five sympatric phylogenetically diverse bacterial strains. Six out of 18 (33%) crude extracts inhibited bacterial growth at natural extract concentrations. The crude extract of the sponge Haliclona viscosa inhibited growth of all five bacterial strains, suggesting the presence of metabolites with broad-spectrum activity. Three active compounds were isolated from H. viscosa having antibacterial properties similar to those of the crude extract. Our data indicate that antibacterial secondary metabolites are present in sub-Arctic marine invertebrates but are less abundant than in temperate, tropical or Antarctic species.