Ramasamy Vijayakumar

Characterization and structure elucidation of antibacterial compound of Streptomyces sp. ECR77 isolated from east coast of India.

AbstractnForty marine actinobacteria were isolated from the sediments of east coast (Bay of Bengal) region of Tamilnadu, India. Morphologically distinct colonies were primarily tested against fish pathogenic bacteria such as Vibrio cholerae, V. parahaemolyticus, V. alginolyticus, Pseudomonas fluorescens and Aeromonas hydrophila by cross-streak plate method. The secondary metabolites produced by the highly potential strain cultured on starch casein broth were extracted separately with various solvents such as alcohol, ethyl acetate, methanol, petroleum ether and chloroform. The antibacterial assay of the bioactive compounds was tested against the fish pathogenic bacteria by well diffusion method. Of the various solvents used, the ethyl acetate extract of the isolate had good antibacterial activity. The potential strain was identified as Streptomyceslabedae by phenotypic, 16S rRNA gene sequence and phylogenetic analysis. Purification of the biologically active compounds by column chromatography led to isolation of 27 fractions. The biologically active fraction was re-chromatographed on a silica gel column to obtain a single active compound, namely N-isopentyltridecanamide. The structure of the compounds was elucidated on the basis of ultra violet, Fourier transform infrared and nuclear magnetic resonance spectra.

Isolation, structure elucidation and antibacterial activity of methyl-4,8-dimethylundecanate from the marine actinobacterium Streptomyces albogriseolus ECR64

Around 120 actinobacterial colonies were isolated from various regions of marine East coast region of Tamil Nadu, India. Among them, 33 were morphologically distinct and they were preliminarily screened for their antibacterial activity against Pseudomonas fluorescens, Vibrio cholerae, V. parahaemolyticus, V. alginolyticus, and Aeromonas hydrophila by cross-streak plate technique. Among the isolated, the isolate ECR64 exhibited maximum zone of inhibition against fish pathogenic bacteria. The crude bioactive compounds were extracted from the isolate ECR64 using different organic solvents which exhibited maximum antibacterial activity. Separation and purification of the bioactive compounds were made by column chromatography which yielded 27 fractions and were re-chromatographed to obtain the active compound. Ultra violet (UV), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectral studies were used to predict the structure of the active compound which was identified as methyl-4,8-dimethylundecanate. The potential isolate ECR64 was identified as Streptomyces albogriseolus by phylogenetic, phenotypic and genotypic (16S rRNA gene sequence) analyses. The identified compound methyl-4,8-dimethylundecanate can be used as potential and alternative drug in disease management of aquaculture.

INVESTIGATION OF PHYSICO-CHEMICAL PROPERTIES OF RHIZOSPHERE SEDIMENTS FROM EAST COAST REGION, TAMIL NADU, INDIA

Objective: The present study was undertaken to evaluate the immunomodulatory activity of the alcoholic extracts of Ruta graveolens leaves in vivo. Methods: Immunomodulatory activity was determined by neutrophil adhesion test, phagocytic activity, haemagglutinating antibody (HA) titre and delayed-type hypersensitivity (DTH) response. Results: Oral administration of the extracts (50, 100, 150 and 200 mg/kg bw, p. o) evoked a significant (**P<0.01) increased in percent of neutrophil adhesion to nylon fibers. Both the extracts were also increased the antibody titre in a dose-dependent manner. Oral administration of both the compound significantly (**P<0.01) potentiated delayed type hypersensitivity reaction induced by sheep red blood cells and response towards phagocytosis in carbon clearance assay. In this study indicated that leaves extracts possesses potent immune-modulatory activity in a concentration-dependent manner. The response was statistically significant when compared with the control (*P<0.05, **P<0.01). Conclusion: The study stated that Ruta graveolens leaves extracts showed a significant stimulation of the cell-mediated immunity as well as humoral immunity. Further investigations are required to determine its active constituents and also its mechanism of action.