Dharumadurai Dhanasekaran

Hepatotoxic effect of ochratoxin A and citrinin, alone and in combination, and protective effect of vitamin E: In vitro study in HepG2 cell

Ochratoxin A (OTA) and citrinin (CTN) are the most commonly co-occurring mycotoxins in a wide variety of food and feed commodities. The major target organ of these toxins is kidney but liver could also be a target organ. The combined toxicity of these two toxins in kidney cells has been studied but not in liver cell. In this study HepG2 cells were exposed to OTA and CTN, alone and in combination, with a view to compare the molecular and cellular mechanisms underlying OTA, CTN and OTA + CTN hepatotoxicity. OTA and CTN alone as well as in combination affected the viability of HepG2 cells in a dose-dependent manner. OTA + CTN, at a dose of 20% of IC50 of each, produced effect almost similar to that produced by either of the toxins at its IC50 concentration, indicating that the two toxins in combination act synergistically. The cytotoxicity of OTA + CTN on hepatocytes is mediated by increased level of intracellular ROS followed/accompanied by DNA strand breaks and mitochondria-mediated intrinsic apoptosis. Co-treatment of vitamin E (Vit E) with OTA, CTN and OTA + CTN reduced the levels of ROS and the cytotoxicity. But the genotoxic effect of OTA and OTA + CTN was not completely alleviated by Vit E treatment whereas the DNA damage as caused by CTN when treated alone was obviated, indicating that OTA induces DNA damage directly whereas CTN induces ROS-mediated DNA damage and OTA + CTN combination induces DNA damage not exclusively relying on but influenced by ROS generation. Taken together, these findings indicate that OTA and CTN in combination affect hepatocytes at very low concentrations and, thereby, pose a potential threat to public and animal health.

Evaluation of larvicidal activity of biogenic nanoparticles against filariasis causing Culex mosquito vector

Objective To evaluate the larvicidal activity of biogenic nanoparticles against filariasis causing Culex mosquito vector.

Screening of biofouling activity in marine bacterial isolate from ship hull.

Biofouling is the undesirable accumulation of microorganisms, plants, algae and animals on submerged structures especially ship hulls. Biofouling also occurs on the surface of living marine organisms. It is also found on membrane systems such as membrane bioreactors and reverse osmosis spiral wound membranes. In the same manner, it is found in cooling water cycles of large industrial equipments and power stations. In the present study, totally 11 isolates were obtained from three ships from Royapuram harbour, Chennai, Tamil Nadu, India. Among the 11 isolates only DR4 showed maximum biofouling activity in the microtiter plate assay with a significant optical density of 0.596. Also an attempt was made to characterize the different biofouling bacterial isolates analyzing their morphological, biochemical and molecular characteristics. The results of the present study based on the above characteristics revealed that the isolate DR4 was similar to Bacillus sp. This study also highlights the need for a safe and natural antifouling agent to control the biofouling bacteria in the marine environment.

Extracellular biosynthesis, characterisation and in-vitro antibacterial potential of silver nanoparticles using Agaricus bisporus

Microbial silver nanoparticles have been known to have bactericidal effects but the antimicrobial mechanism has not been clearly revealed. The use of microorganisms in the synthesis of nanoparticles emerges as an ecofriendly and exciting approach. Here we report on the extracellular synthesis method for the preparation of silver nanoparticles in water using the extract of Agaricus bisporus, a naturally occurring edible mushroom, as reducing and protecting agents. The silver nanoparticles were characterised by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) analysis. The synthesised silver nanoparticles showed antibacterial activity against the multi-drug resistant Gram positive and Gram negative bacterial pathogens.

Preclinical evaluation and molecular docking of 4-phenyl-1-Napthyl phenyl acetamide (4P1NPA) from Streptomyces sp. DPTB16 as a potent antifungal compound

The incidence of fungal disease has increased dramatically over the past decades, mainly due to the emergence and transmission of antifungal resistance within the fungal pathogens. The present study investigates the use of novel antifungal compound 4-Phenyl-1-Napthyl Phenyl Acetamide (4P1NPA), isolated from marine Streptomyces sp. DPTB16 as a potent antifungal drug. The preclinical studies and molecular docking for 4P1NPA against Cytochrome P450 51 (CYP 51) were performed using in silico pharmacology and docking tools. The finding reveals the drug likeliness of 4P1NPA and satisfactory interaction of 4P1NPA with CYP 51. These results collectively evidence the use of 4P1NPA as a drug to treat fungal infections. On the whole, we highlight the findings of this research will be helpful to design 4P1NPA as novel antifungal drug to defend the emerging antifungal resistance.

Herbicidal agents from actinomycetes against selected crop plants and weeds

About 64 total actinomycetes were isolated from various coastal soils. Sixteen actinomycete isolates were screened for herbicidal principles. Out of these, five potent isolates were selected for characterisation and identification. Based on their morphological, biochemical and physiological characteristics, the actinomycete isolates were identified as Glyomyces, Saccharomonospra and Streptomyces sp. The Streptomycetes isolates were tested for herbicidal principles by germination inhibition assay. About 10 crop seeds were tested for herbicidal activity with Streptomycetes isolates. The crop seeds did not show growth inhibition. Four weed seeds were tested for herbicidal activity with Streptomyces isolates. Streptomyces inhibits the growth of Echinochilora crusgalli, but it could not inhibit the growth of Echinochilora colonum, Parthenium sp., or Ageratum conizoites. The present study concludes that Streptomyces isolates will be a bioherbicide against E. crusgalli. Further study is required to confirm the activity of Streptomyces isolates against E. crusgalli under field conditions.

Synthesis and bio-catalytic activity of isostructural cobalt(III)-phenanthroline complexes

AbstractWe have synthesized two isostructural mononuclear cobalt(III) complexes [1]NO3⋅3H2O and [1]NO3⋅CH3CO2H⋅H2O {[1]+ = [Co(1,10-phenanthroline)2Cl2]+} and characterized by single crystal X-ray structural analyses. Mass spectral studies of the complexes indicate both the compounds to produce identical cationic species viz., [Co(phen)2Cl2]+ in methanol solution. [1]+ has been evaluated as model system for the catechol oxidase enzyme by using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate in methanol medium, which revealed that the cationic complex efficiently inhibits catalytic activity with kcat value 9.65 ×102 h−1. [1]+ cleaved pBR 322 DNA without addition of an activating agent. Further, the anti-cancer activity of [1]+ on human hepatocarcinoma cell line (HepG2) has been examined. The induction of apoptosis induced in the cell line was assessed base on the changes in cell morphology, which showed the efficacy of [1]+ to induce apoptosis in 53% of cells during 24 h treatment. Interestingly, the observed IC50 values reveal that [1]+ brings about conformational change on DNA strongly and exhibits remarkable cytotoxicity. The cationic cobalt(III) complex exhibits good catalytic activity in saturated oxygen environment towards 3,5-ditertbutylcatechol with kcat value 9.65×102 h-1. It also exhibits important cytotoxicity against human hepatocarcinoma cell line (HepG2).

Allelopathic effect of actinobacterial isolates against selected weeds

The taxonomic characteristics of weeds such as morphology of shoot, leaves, flowers, stem, fruits and seeds were recorded as Gynandropsis pentaphylla, DC, Amarantus spinosus Linn, Cyperus rotundus, Amarantus viridis Linn, Cassia occidentalis, Linn and Echinochilora orygicola. Totally 20 actinobacteria isolates were screened for herbicidal activity against the weed. Among the 20 isolates, only four actinobacterial isolates KA1-3, KA1-4, KA1-7 and KA23A showed significant herbicidal activity against C. rotundus. The herbicidal effect of actinobacterial culture filtrates on germination and seedling growth of C. rotundus was tested. The shoot and root growth of C. rotundus was severely affected when compared to control. The potent actinobacterial isolates KA1-4 and KA1-7 were characterised based on their morphological and molecular phylogenetic property and were identified as Streptomyces sp. The present study concludes that actinobacterial isolates will be used as bioherbicide against C. rotundus. Further studies are required to confirm the activity of actinobacterial isolates against C. rotundus under field conditions.

Isolation, characterisation and antifungal activity of marine actinobacteria from Goa and Kerala, the west coast of India

In total, 53 marine actinobacteria were isolated from the soils of six different locations in Goa and Kerala, on the west coast of India. All the isolates were screened for their antifungal properties against some phytopathogenic fungi by dual culture experiments. Among the 53 actinobacterial isolates, five isolates inhibited the growth of phytopathogens, namely Colletotrichum falcatum, Thielaviopsis paradoxa and Fusarium semitectum. But none of them were effective against Aspergillus niger, Aspergillus candidus and Aspergillus flavus. The antifungal activity of the actinobacteria was tested by food poisoning techniques, using four different concentrations (0.5%, 1.0%, 1.5% and 2.0%) of cell-free culture filtrates, which showed promising activity (almost 100% inhibition) against three pathogenic and one non-pathogenic fungi at 2% extract concentration. A comparison of the antifungal activity of the actinobacteria was also made with three commercial fungicides, namely hexaconazole, thiophanate methyl and propiconazole. The identity of the antagonistic actinobacteria was confirmed based on the morphological, cultural, biochemical, chemo-taxonomical and physiological characteristics. Among 5 antagonistic isolates, three antagonistic isolates were assigned to the genus Streptomyces, Nocardiopsis (1) and Saccharopolyspora (1).

Multi-functional nano silver: A novel disruptive and theranostic agent for pathogenic organisms in real-time

The present study was aimed at evaluating the fluorescence property, sporicidal potency against Bacillus and Clostridium endospores, and surface disinfecting ability of biogenic nano silver. The nano silver was synthesized using an actinobacterial cell-filtrate. The fluorescence property as well as imaging facilitator potency of this nano silver was verified adopting spectrofluorometer along with fluorescent and confocal laser scanning microscope wherein strong emission and bright green fluorescence, respectively, on the entire spore surface was observed. Subsequently, the endospores of B. subtilis, B. cereus, B. amyloliquefaciens, C. perfringens and C. difficile were treated with physical sporicides, chemical sporicides and nano silver, in which the nano silver brought about pronounced inhibition even at a very low concentration. Finally, the environmental surface-sanitizing potency of nano silver was investigated adopting cage co-contamination assay, wherein vital organs of mice exposed to the nano silver-treated cage did not show any signs of pathological lesions, thus signifying the ability of nano silver to completely disinfect the spore or reduce the count required for infection. Taken these observations together, we have shown the multi-functional biological properties of the nano silver, synthesized using an actinobacterial cell-filtrate, which could be of application in advanced diagnostics, biomedical engineering and therapeutics in the near future.