International conference on Frontiers in Chemical Technology 2020 (FCT 2020)
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Item Exploring bioactive compounds in the endolichenic fungus, Xylaria feejeensis, inhabiting the lichen, Graphis librata, collected from Negombo lagoon, Sri Lanka(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Gunawardhana, M. H. A. Y.; Wickramarachchi, P. A. S. R.; Weerasinghe, W. R. H.; Paranagama, P. A.The accelerating pharmaceutical problem of bacteria growing resistant to existing antibiotics forces the scientific community to search for new antibacterial compounds for antibiotic drug development. Literature reveals that Sri Lankan mangrove inhabiting endolichenic fungal (ELF) population is rich in many such bioactive compounds. Previously isolated and cultured ELF, Xylaria feejeensis; from the lichen Graphis librata inhabiting in the mangrove plant Rhizophora mucronata was cultured on 60 large potato dextrose agar medium containing petri dishes and incubated for 14 days at room temperature. After extracting secondary metabolites to ethyl acetate (EA) the resulted crude extract was tested for its antibacterial and antioxidant activity. EA crude extract showed negligible antioxidant activity in DPPH radical scavenging assay hence this assay was not proceeded further. The activity of crude extract (5 mg/ml) against Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923) and Bacillus subtilis (ATCC6051) was tested using agar well diffusion antibacterial assay. An inhibition zone diameter of 1.9 cm, 2.2 cm, and 2.2 cm against three bacterial strains with Azithromycin positive control (5 mg/ml) 2.2 cm, 2.2 cm and 2.3 cm was observed respectively. By partitioning of EA crude extract resulted two antibacterial active hexane and chloroform fractions and one antibacterial inactive 60% methanol in water fraction. Hexane fraction showed the highest antibacterial activity with inhibition diameter zone of 2.6 cm against E.coli with 2.6 cm diameter of inhibition zone for positive control. Further purification of hexane fraction was performed by normal phase column chromatography and 4 fractions were resulted. The highest polar fraction showed 1.4, 2.1 and 1.7 cm diameter inhibition zones of growth of E.coli, S. aureus and B. subtilis comparable with 2.2 cm Azithromycin. The other 3 fractions showed no antibacterial activity against these bacterial strains. Results suggest that further purification of active fraction and structure elucidation might result in new antibiotic lead compounds.Item Qualitative analysis of heavy metal adsorption by the green synthesized silver nanoparticles(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Ramanayake, R. A. D. J.; Wickramarachchi, P. A. S. R.Silver nanoparticles (AgNPs) have attracted high research interest because of their important applications in antimicrobial, catalysis, and water treatment plants. They display totally new and enhanced properties compared to larger bulk material particles and these novel properties are due to the difference in specific characteristics such as particle size, distribution, morphology and higher surface area-to-volume ratio. The aim of this research was to determine the Pb(II) and Cu(II) adsorption of synthesized AgNPs using natural polymer, chitosan as both reducing and capping agent. AgNPs were formed in an autoclave at 15 psi and 131 0C by varying the AgNO3 and chitosan concentrations and autoclaving time. AgNPs solution thus obtained was mixed with Pb(II) and Cu(II) (0.05, 10, 100, 200, 500 ppm) solution separately and kept overnight. The removal of metal ions from the solution was monitored by the shift and intensity variation of the surface plasmon resonance (SPR) band of the AgNPs. The green synthesized silver nanoparticles were characterized using ultra violet visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) and particle size analyzer. UV-Vis peak at the 430 nm confirmed the formation of chitosan stabilized silver nanoparticles. The dynamic light scattering (DLS) measures confirmed that the average size of synthesized AgNPs was 818.4 nm with the polydispersity index of 0.243 revealing the uniform size and good dispersion of the nanoparticles. The optimum concentrations of AgNO3 and chitosan were recorded as 50 mM and 2% respectively. The maximum yield of nanoparticles was obtained at 60 minutes of autoclaving, which was decided as the optimum time of autoclaving. After addition of metal ions, AgNPs solutions showed a color change and a shift and variation in intensity of the SPR band at lower metal ion concentrations while at higher metal concentrations SPR band disappeared indicating the adsorption of metal ions onto the AgNPs. Hence this has the potential to be developed as a heavy metal removal technique in water.