Production, optimization and characterization of partially purified anti-mycotic compound from marine soil derived streptomycetes originating at unexplored region of Bay of Bengal, India.

Sixty-eight morphologically distinct isolates of marine actinomycetes were derived from seashore, mangrove, and saltpan ecosystems located between the Palk Strait and Gulf of Mannar region, Bay of Bengal, Tamilnadu. Twenty-five (36.8%) isolates exhibited anti-mycotic activity against Candida albicans and Cryptococcus neoformans in preliminary screening, and 4 isolates with prominent activity were identified and designated at the genus level as Streptomyces sp. VPTS3-I, Streptomyces sp. VPTS3-2, Streptomyces sp. VPTSA1-4 and Streptomyces sp. VPTSA1-8. All the potential antagonistic isolates were further characterized with phenotypic and genotypic properties including 16S rRNA gene sequencing and identified species level as Streptomyces afghaniensis VPTS3-1, S. matensis VPTS3-2, S. tuirus VPTSA1-4 and S. griseus VPTSA1-8. In addition, the active fractions from the potential antagonistic streptomycetes were extracted with organic solvents by shake flask culture method and the anti-mycotic efficacies were evaluated. The optimization parameters for the production of the anti-mycotic compound were found to be pH between 7 and 8, the temperature at 30ᵒC, the salinity of 2%, incubation of 9 days, and starch and KNO3 as the suitable carbon and nitrogen sources respectively in starch casein medium.

Desert actinobacteria as a source of bioactive compounds production with a special emphases on Pyridine-2,5-diacetamide a new pyridine alkaloid produced by Streptomyces sp. DA3-7.

In the present study, 134 morphologically distinct actinobacteria isolates were obtained from soil samples from 10 different localities in the Saudi Arabian desert. The preliminary screening revealed that 16 of these isolates possessed antimicrobial activity. One isolate, which was identified as Streptomyces sp. DA3-7, possessed broad-spectrum antimicrobial activity against both gram-positive and gram-negative bacteria, as well as against fungi, and modified nutrient glucose medium was suitable for Streptomyces sp. DA3-7 to produce extracellular metabolites. The ethyl acetate extract of Streptomyces sp. DA3-7 exhibited antimicrobial activity against Enterococcus faecalis and Salmonella typhimurium, with minimum inhibitory concentrations of 78 and 156µg/mL, respectively, as well as strong cytotoxicity (24h IC50 85µg/mL) against MCF-7 human breast adenocarcinoma cells. The active compound was separated, purified, and identified as Pyridine-2,5-diacetamide (C9H11N3O2+H+, 194.21), which possessed a lowest minimum inhibitory concentration (31.25µg/mL) against both Escherichia coli and Cryptococcus neoformans. The antimicrobial activities of this novel compound are reported here for the first time.

Purification, characterization, and statistical optimization of a thermostable α-amylase from desert actinobacterium Streptomyces fragilis DA7-7.

In this study, preliminary screening revealed that of 134 desert soil actinobacterial isolates, only 43 isolates produced amylase. Among these, an isolate DA7-7, which was identified as Streptomyces fragilis DA7-7, showed a prominent zone of clearance and significant amount of α-amylase production. The pre-optimization studies showed varying physicochemical and nutrients properties of the medium influenced the enzyme production significantly. Consequently, central composite design was employed with the selected variables (pH, temperature, dextrose, and peptone) for α-amylase production. The optimum fermentation conditions were 3.07% dextrose, 1.085% peptone, pH 6.0, and incubation temperature 27.27 °C. The predicted optimum α-amylase activity was 991.82 U/mL/min, which was similar to the experimental amylase activity of 973.5 U/mL/min. The crude α-amylase produced by S. fragilis DA7-7 was purified with ammonium sulfate precipitation, followed by gel filtration chromatography, and the estimated molecular mass was 51 kDa. The purified α-amylase was stable under the following conditions: pH (4-9), temperature (40-80 °C), NaCl (1-4 M), and detergents (1-10 mM). The Km and Vmax values of enzyme were found to be 0.624 mU/mg and 0.836 mg/mL, respectively.

Antifeedant, larvicidal and growth inhibitory bioactivities of novel polyketide metabolite isolated from Streptomyces sp. AP-123 against Helicoverpa armigera and Spodoptera litura.

BACKGROUND: Considerable attention has been paid to actinomycetes, especially the secondary metabolites obtained from Streptomyces species, as the best alternatives to chemicals as biological control agents for polyphagous pests such as Helicoverpa armigera and Spodoptera litura. On the basis of their novel biocontrol attributes, novel polyketide metabolite isolated from marine Streptomyces sp. AP-123 exhibited significant antifeedant, larvicidal and growth inhibitory activities against polyphagous pests. RESULTS: Leaf disc no-choice method was used for the insect bioassay. The polyketide metabolite presented significant antifeedant activities against H. armigera (78.51%) and S. litura (70.75%) at 1000 ppm concentration. The metabolite also exhibited high larvicidal activities against H. armigera (63.11%) and S. litura (58.22%) and the LC50 values were 645.25 ppm for H. armigera and 806.54 ppm for S. litura. The metabolite also prolonged the larval-pupal duration of the insects at all the tested concentrations. CONCLUSIONS: The activities of the polyketide metabolite were concentration dependent for both the insects therefore it could be used as an agent to prepare new pesticidal formulations.

Antimicrobial, antimycobacterial and antibiofilm properties of Couroupita guianensis Aubl. fruit extract.

BACKGROUND: Couroupita guianensis Aubl. (Lecythidaceae) is commonly called Ayahuma and the Cannonball tree. It is distributed in the tropical regions of northern South America and Southern Caribbean. It has several medicinal properties. It is used to treat hypertension, tumours, pain, inflammatory processes, cold, stomach ache, skin diseases, malaria, wounds and toothache. METHODS: The fruits of Couroupita guianensis were extracted with chloroform. Antimicrobial, antimycobacterial and antibiofilm forming activities of the chloroform extract were investigated. Quantitative estimation of Indirubin, one of the major constituent, was identified by HPLC. RESULTS: Chloroform extract showed good antimicrobial and antibiofilm forming activities; however it showed low antimycobacterial activity. The zones of inhibition by chloroform extract ranged from 0 to 26 mm. Chloroform extract showed effective antibiofilm activity against Pseudomonas aeruginosa starting from 2 mg/mL BIC, with 52% inhibition of biofilm formation. When the chloroform extract was subjected to HPLC-DAD analysis, along with Indirubin standard, in the same chromatographic conditions, it was found that Indirubin was one of the major compounds in this plant (0.0918% dry weight basis). CONCLUSIONS: The chloroform extract showed good antimicrobial and antibiofilm properties. Chloroform extract can be evaluated further in drug development programmes.

Antimicrobial activity of sesquiterpene lactones isolated from traditional medicinal plant, Costus speciosus (Koen ex.Retz.) Sm.

BACKGROUND: Costus speciosus (Koen ex.Retz.) Sm (Costaceae) is an Indian ornamental plant which has long been used medicinally in traditional systems of medicine. The plant has been found to possess diverse pharmacological activities. Rhizomes are used to treat pneumonia, rheumatism, dropsy, urinary diseases, jaundice, skin diseases and leaves are used to treat mental disorders. METHOD: Antibacterial and antifungal activities were tested using Disc diffusion method and Minimum Inhibitory Concentration (MIC). Column chromatography was used to isolate compounds from hexane extract. X-ray crystallography technique and GC-MS analysis were used to identify the compounds RESULTS: Antibacterial and antifungal activities were observed in hexane, chloroform, ethyl acetate and methanol extracts. Hexane extract of C.speciosus showed good activity against tested fungi also. Two sesquiterpenoid compounds were isolated (costunolide and eremanthin) from the hexane extract. Both the compounds did not inhibit the growth of tested bacteria. But, both the compounds inhibited the tested fungi. The compound costunolide showed significant antifungal activity. The MIC values of costunolide were; 62.5 µg/ml against Trichophyton mentagrophytes, 62. µg/ml against T. simii, 31.25 µg/ml against T. rubrum 296, 62.5 µg/ml against T. rubrum 57, 125 µg/ml against Epidermophyton floccosum, 250 µg/ml against Scopulariopsis sp, 250 µg/ml against Aspergillus niger, 125 µg/ml against Curvulari lunata, 250 µg/ml against Magnaporthe grisea. CONCLUSION: Hexane extract showed promising antibacterial and antifungal activity. The isolated compound costunolide showed good antifungal activity.