Browsing by Author "Wickramarachchi, P.A.S.R."

Now showing 1 - 12 of 12

Activity of chitosan films containing rhizome oil of Alpinia malaccensis against Escherichia coli and Staphylococcus aureus
(Sri Lanka Association for the Advancement of Science, 2014) Samaratunge, I.N.; Wickramarachchi, P.A.S.R.
Antifungal activity of chitosan films containing dry rhizome oil of Alpinia malaccensis against Colletotrichum musae
(Sri Lanka Association for the Advancement of Science, 2013) Rasangika, W.P.M.; Wickramarachchi, P.A.S.R.
Comparative study on larvicidal activity of green synthesized silver nanoparticles and Annona glabra (Annonaceae) aqueous extract to control Aedes aegypti and Aedes albopictus (Diptera: Culicidae)
(Heliyon 6, 2020) Amarasinghe, L.D.; Wickramarachchi, P.A.S.R.; Aberathna, A.A.A.U.; Sithara, W.S.; De Silva, C.R.
The present study reports mosquito larvicidal potential of green synthesized silver nanoparticles by using Annona glabra leaves (An-AgNPs). Synthesized An-AgNPs were characterized by Ultraviolet-Visible spectroscopy (UVVIS), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS) technique and Fourier transform infrared spectroscopy (FTIR). Colur change from pale yellow to brick red of the plant extract and AgNO3 solution indicated the formation of An-AgNPs initially. Surface Plasmon Resonance (SPR) band at 435 nm in the UV-Vis confirmed the formation of An-AgNPs. SEM images showed that An-AgNPs were spherical in shape. FTIR proved that An-AgNPs were functionalized with biomolecules in A. glabra leaves. Based on DLS analysis the average size range of synthesized An-AgNPs was determine to be 10–100 nm and 100–1000 nm. Third instar larvae of dengue vector mosquitoes, Aedes aegypti and Aedes albopictus were subjected to larvicidal bioassays in a range of concentrations of An-AgNPs and A. glabra crude aqueous leaf extract (2–10 mg/L). AnAgNPs exhibited very high larvicidal activity against dengue vector mosquito larvae; LC50 value for Ae. aegypti at 24 h exposure to An-AgNPs (Plant extract: AgNO3 1 : 10) 5.29 mg/L; An-AgNPs (Plant extract: AgNO3 2 : 10) 2.43 mg/L while LC50 value for Ae. albopictus at 24 h exposure to An-AgNPs (Plant extract: AgNO31:10) 3.02 mg/ L; An-AgNPs (Plant extract: AgNO3 2:10) 2.51 mg/L. LC50 values obtained for A. glabra leaf extract tested against Ae. aegypti and Ae. albopictus are 5.94 mg/L and 5.00 mg/L respectively at 24-hour exposure. This study further revealed that Ae. albopictus is more susceptible than to Ae. aegypti to a given concentration of An-AgNPs and to crude aqueous leaf extract of A. glabra. Larvicidal effect of An-AgNPs is superior to the crude aqueous leaf extract of A. glabra. An-AgNPs is a potent larvicide for dengue vector control.
The effect of changing the oil concentration on oil content, encapsulation efficiency and release rate of cinnamon leaf oil encapsulated chitosan microcapsules.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Muthumali, A.M.T.; Wickramarachchi, P.A.S.R.
Antibiosis, insect repelling and stress reducing properties of essential oils have been widely studied and well established. However, the release speeds of these compounds are usually high. Encapsulation is one of the effective methods commonly used to control the release and to increase the bioavailability of these compounds. In this research, cinnamon leaf oil was incorporated into chitosan microcapsules (MCs) to achieve the above mentioned goals. Here, we investigated the effect of changing the oil concentration on oil load, oil content, encapsulation efficiency and release rate of MCs. MCs were prepared by decreasing the solubility of chitosan. Briefly, NaOH was dripped into pre-prepared oil-chitosan emulsion, with slow stirring. Glutaraldehyde (10 mmol/g of polymer) was used for further crosslinking of chitosan wall of MCs. The average particle size was determined using the stage micrometer. Oil release was studied by UV-visible spectrophotometry. Oil release, encapsulation efficiency, oil content and oil load in MCs were calculated. All the parameters were dependent on the amount of oil. The particle size, encapsulation efficiency, oil content and release rate of cinnamon oil increased with the increase in oil loading. Scanning electron microscopy study showed a change in surface characteristics of the microcapsules due to cinnamon oil loading.
Encapsulation of 1,8-cineole with chitosan by emulsion formulation: optimization of parameters for a stable imulsion
(Sri Lanka Association for the Advancement of Science, 2013) Alahakoon, U.V.S.H.; Wickramarachchi, P.A.S.R.
Exploring bioactive compounds in the endolichenic fungus, Xylaria feejeensis, inhabiting the lichen, Graphis librata, collected from Negombo lagoon, Sri Lanka
(Proceedings of the 1st International Conference on Frontiers in Chemical Technology, Institute of Chemistry Ceylon, 2020) Gunawardhana, M.H.A.Y.; Wickramarachchi, P.A.S.R.; Weerasinghe, W.R.H.; Paranagama, P.A.
The accelerating pharmaceutical problem ofbacteria growing resistant to existing antibrotics forces the scientific community to search for new antibacterial compounds for antibiotic drug development. I-iterature reveals that Sri Lankan mangrove inhabiting endolichenic fungal (ELF) population is rich in nrany such bioactive compounds- Previously isolated and cultured ELF, Xylaria feejeensis; ftom the lichen Graphis librata inhabiting in the mangrove phnt Rhizophora mucronata was culrured 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 shou,ed negligible antioxidant activity in DPPH radical scavenging assay hence this assay was not proceeded further. The activity ofcrude extract (5 mg/ml) agatnstEscherichia coli (ATCC25922), Staphylococcus aureus (NCC25923) utd Bacillus subtilis (ATCC605I) was tested using agar well diffirsion antibacterial assay. An inhibition zone diameter of 1.9 cm, 2.2 cm, ar,d 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 607o methanol in water fraction. Hexane fraction showed the highest antibacterial activity with inhibition diameter zone of 2.6 cm against E.coll with 2.6 cm diameter of inhibition zone for positive control. Further purification ofhexane fraction was performed by normal phase column chromatography and 4 fractions were resulted. The highest polar fraction showed L4, 2.landl.TcmdiameterinhibitionzonesofgroMhofE.coli,S. aureusutdB.sr.rbtillscomparablewith 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.
A Novel Cytotoxic Compound From the Endolichenic Fungus, Xylaria psidii Inhabiting the Lichen, Amandinea medusulina
(Natural Product Communication, 2020) Santhirasegaram, S.; Wickramarachchi, P.A.S.R.; Attanayake, R.N.; Weerakoon, G.; Samarakoon, S.; Wijeratne, K.; Paranagama, P.A.
The lichen host, Amandinea medusulina, collected from mangrove habitats in Sri Lanka, and its associated endolichenic fungi were isolated and identified by rDNA-ITS sequence analysis and morphological features. One of the fungal strains frequently isolated from the lichen thalli was identified as Xylaria psidii. This study aimed at the isolation and identification of the cytotoxic compounds present in this fungus. Secondary metabolites of X. psidii were first extracted into ethyl acetate and subsequently subjected to bioassay-guided fractionation to isolate the bioactive compounds. Sulforhodamine B assay against a lung cancer (NCI-H292) cell line was used to determine the differential cytotoxic activity. Bioassay-guided fractionation led to the isolation of an active compound, SS/02/29/08, showing moderate cytotoxicity (IC50 = 27.2 µg/mL). Its structure was elucidated by IR, 1D- and 2D-NMR, and 13C-NMR spectrophotometry and MS, in combination with HRMS, 13C NMR, HSQC, HMBC, and DQF-COSY. The structure of SS/02/29/08 was determined as (Z)-3-{(3-acetyl-2-hydroxyphenyl)diazenyl}-2,4-dihydroxybenzaldehyde and identified as a new compound. This novel compound has promising differential cytotoxic activity against human lung cancer cell line (NCI-H292).
Photocatalytic Activity of Biosynthesized of Silver Nanoparticles Using Leaf Extract of Annona glabra
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Paragodaarachchi, Y.L.; Wickramarachchi, P.A.S.R.; De Silva, C.; Amarasinghe, L. D.
Recently metallic nanoparticles were found to possess photocatalytic activity on organic molecules under visible radiation a phenomenon which will be useful in degrading and removing hazardous organic dyes. During this study the photocatalytic activity of Annona glabra - AgNPs (bare NPs) and Tween 80-stabilized Annona glabra – AgNPs (stabilized NPs) was studied by monitoring the degradation of methylene blue as a model dye. AgNPs were synthesized by incubating the leaf extract of A. glabra (2 mL) with silver nitrate (1 mM, 20.00 mL) for 3 hours. The solution was kept under dark conditions with continuous slow agitation. The solution was centrifuged at 6000 rpm for 20 minutes to separate the AgNPs and NPs were washed with water. The synthesized AgNPs were characterized using UV – Visible spectrometer, particle size analyzer, scanning electron microscope. In order to synthesize stabilized AgNPs, biofabricated AgNPs as above were ultrasonicated for 15 mins and added to a solution of Tween 80 (1% w/v, 20.0 mL) and kept stirring for 3 hours. To determine the photocatalytic activity, above prepared AgNPs (25mg/mL, 2.0 mL) were added to a Methylene blue solution (1 x 10-5 M, 50.0 mL). The suspension was stirred under dark conditions for 30 mins. It was exposed to sunlight under slow agitation. Photodegradation was monitored at 30-minute intervals by withdrawing 5 mL aliquots of AgNP added methylene blue solution. The aliquots were centrifuged, and the absorbance was measured using the UV-Visible spectrophotometer at 665for a period of 3 hours. The AgNPs are spherical in shape and show a characteristic absorbance peak at 417 nm. This peak is due to the surface plasmon resonance of the AgNPs. The average size range of the nanoparticles is 10 – 190 nm. Methylene blue solution with added AgNPs became opaque overtime. Initially, the methylene blue solution with bare AgNPs showed subtle reduction of absorbance of the solution. Then the reduction of absorbance was leveled off near the end of the experiment. The absorbance decreased from 0.985 to 0.796 within a period of 3 hours which is a 19.19% reduction of the initial absorbance of the solution. The opacity of the methylene blue solution with stabilized AgNPs increased only by the end of the experiment. Stabilized AgNPs showed methylene blue degradation with higher efficiency than bare AgNPs. The absorbance of the solution reduced from 1.361 to 0.145 within a period of 3 hours which is an 89.34% reduction of the initial absorbance of the solution. Both bare and Tween 80-stabilised AgNPs showed photocatalytic activity on the degradation of methylene blue. The Photocatalytic activity was enhanced by the stabilization of biogenic A. glabra AgNPs with Tween 80.
Qualitative analysis of heavy metal adsorption by the green synthesized silver nanoparticles,
(Proceedings of the 1st International Conference on Frontiers in Chemical Technology, Institute of Chemistry Ceylon, 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, cataiysis, and water treatment plants. They dispray totarly new and. errhanced 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 ofthis research was to determine the pb(II) and cu(II) adsorpdon of synthe,;ized AgNps using natural polyrner, chitosan as both reducing and capping agent. AgNPs were formed in an autoclave at 15 pEi and l3I 0c by varying the AgNo, and chitosan concentrations and autoclaving time. AgNPs solution thus obtained was mixed with pbill) and cu(II) (0'05,10,100,200,500ppm)solutionseparatelyand keptovernight. Theremovalofmetarionsfrom the solution was monitored by the shift and intensityvariation ofthe surface plasmon resonance (SpR) band of the AgNPs' The Sreen synthesized silver nanoparticles were characterized using ultra violet vtsible (uV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning erectron microscope (SEM) and particle size anallzer. UV-Vis peak at the 430 nm confirmed the formation of chitosan stabilized silver nanoparticles. The dynamic light scaftering (DLS) measures confirmed that the average size ofsynthesized AgNPs was 818.4 nm with the polydispersity index of0.243 revealing the uniform size and good dispersion ofthe nanoparticles. The optimum concentrations ofAgNo. and chitosan were recorded as 50 mM and 2% respectively. The maximum yield ofnanoparticles was obtained at 60 minutes of autoclaving, which was decided as the optimum time of autoclaving. After addition of meta.l ions, AgNPs solutions showed a color change and a shift and variation in intensity rif the SPR band at lower metal ion concentrations while at higher metnl concentrations SpR band disappeared indicating the adsorption ofmetal ions onto the AgNps. Hence this has the potential to be developed as a heavy metal removal technique in water.
A review on plant mediated synthesis of silver nanoparticles as a greener approach
(University of Kelaniya, Sri Lanka, 2021) Wickramarachchi, P.A.S.R.; Paragodaarachchi, Y.L.
Metal nanoparticles are used in all phases of science, including medical fields. They still seduce scientists to explore new dimensions for their respective value, which is usually attributed to their corresponding small sizes. Among the other metallic nanoparticles, silver nanoparticles (AgNPs) aroused a keen interest. The chemical methods used to synthesize AgNPs involve reducing and stabilizing agents, which subsequently become risks to the environment. For these reasons, the green synthesis of AgNPs is a significant area of interest. Among the variety of biological molecules used to synthesize AgNPs, the biological molecules obtained in the form of plant extracts are superior to others because of the ease of handling and the reduction of costs. Many plant parts have been used to synthesize AgNPs such as whole plants, leaves, seeds, bark etc. The synthesis of AgNPs by plant extracts is due to the presence of a large amount of organic chemicals such as carbohydrates, fats, proteins, enzymes and coenzymes, phenolic flavonoids, terpenoids, alkaloids, gum, etc., capable of donating an electron to reduce Ag+ ions to Ag0. The active ingredient responsible for the reduction of Ag+ ions varies depending on the extract used. The size and size distribution of AgNPs synthesized with plant extracts depend on plant extract concentration, silver nitrate concentration, pH of the medium, incubation time and temperature. These factors can be modified to refine the properties of AgNPs. Almost all of these conditions have an optimal value to obtain smaller size AgNPs with a narrow size distribution.
Synthesis of Chitosan Stabilized Silver Nanoparticles using Gamma Ray Irradiation and Characterization
(University of Kelaniya, 2011) Hettiarachchi, M.A.; Wickramarachchi, P.A.S.R.
Chitosan stabilized silver nanoparticles (AgNPs) were synthesized using gamma ray irradiation. Four different sample solutions were prepared [1 mM AgNO3 in 0.1% (w/v) chitosan, 1 mM AgNO3 in 0.5% (w/v) chitosan, 2 mM AgNO3 in 0.1% (w/v) chitosan 2 mM AgNO3 in 0.5% (w/v) chitosan] with controls maintaining dose of radiation at 20±2 kGy. The formation of AgNPs were determined by the appearance of the characteristic colour of the AgNPs, using the surface plasmon resonance band (SPR) at 400-432 nm range and the N-H band of the FT-IR spectrum. Stability of the maximum absorption wave lengths of the samples was monitored for three months by UV-visible spectroscopy. The particle size distribution of the stabilized sample, showed a wide distribution of 28-1106 nm. The sample, 2 mM AgNO3 in 0.5% (w/v) chitosan was stable for three months. FT-IR spectroscopic analysis revealed a shifting of N-H stretching vibration band from 3367-3228 cm-1 with the introduction of nanoparticles.
Toxic potential of green synthesized silver nanoparticles using Annona glabra leaf extract against Daphnia magna
(Proceedings of the 1st International Conference on Frontiers in Chemical Technology, Institute of Chemistry Ceylon, 2020) Paragodaarachchi, Y.L.; Wickramarachchi, P.A.S.R.; De Silva, C.R.; Amarasinghe, L.D.
This study aims to evaluate the acute toxicity of biosynthetic AgNPs produced using Annona glabra leaf extract, against a selected aquatic-indicator, Daphnia magna. The toxicity of the biosynthetic AgNPs was compared against the Ag+ ion solution. Aqueous leaf extracts of A. glabra were prepared by heating chopped leaves (20.0 g) with water (100.0 mL) at 100 oc for 1 hour. AgNPs were synthesized by incubating the leaf extract of A. glabra (2 mL) with AgN03 solution (l mM, 20 mL) for 3 hours. The formed AgNPs were separated using centrifugation (6000 rpm, 20 minutes) and the separated AgNPs were freeze dried. AgNPs were Characterized by UV — visible Spectrometer, particle size analyzer and scanning electron microscopy. acute toxicity tests against D. magna were conducted according to the Organization for Economic Co-operation and Development (OECD) standard procedure using neonates aged less than 24 hours reproduced using parthenogenesis. D. magna neonates were exposed to solutions within the concentration range Of 0.01 — 10 mg/L Of AgNP solutions and concentration range Of 0.5 — 2 gg/L Of ion solutions for 48 hours. Tests were conducted in quadruplicate and 95% confidence interval was calculated. Biosynthesized AgNPs showed a plasmon resonance peak at 419 nm, were spherical in shape and the size ranged between 10 — 190 nm. The EC50 value against D. magna for Agt ions were 1.41 ± 0.2 gg/L and for AgNPs it was 3.96 ± 1.1 mg/L after 48 hours. Results obtained from this study suggests that the toxicity ofbiosynthetic A. glabra - AgNPs exerts lesser toxic effect to D. magna than the Agt ions.