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Item Antioxidant, a-Amylase Inhibitory Activities and Photoprotective Properties of Peels of Nephelium Lappaceum Linn. (Malwana Special)(Oriental Journal of Chemistry, 2021) Binuwangi, A.K.D.M.; Perera, M.P.J.; Silva, A.A.G.; Attanayake, R.N.; Rajapakse, C.S.K.This study focused on evaluation of antioxidant, α-amylase inhibitory activities and photo protective properties of peels of Nephelium lappaceum Linn. (rambutan); Malwana special. Methanolic extract of peels was sequentially partitioned in hexane, dichloromethane (DCM) and aqueous methanol. The methanol extract showed a significantly (p greater then 0.05) higher DPPH radical scavenging activity than that of butylated hydroxytoluene. Among the fractions, the highest total phenolic content (TPC) was found in the aqueous methanol fraction. DCM and aqueous methanol fractions were rich in flavonoids. In vitro α-amylase inhibitory activity of the aqueous methanol fraction was also significantly higher than the standard drug, acarbose. Partially purified aqueous methanol fraction of rambutan peels exhibited UV-B absorption with a moderate solar protection factor. The results revealed that the peels of Nephelium lappaceum Linn., Malwana special can be considered as a promising source for the development of natural antioxidant, cosmeceutical sunscreen and antidiabetic agents.Item Decaying Hardwood Associated Fungi Showing Signatures of Polyethylene Degradation(BioResources, 2021) Perera, P.; Deraniyagala, A.S.; Mahawaththagea, M.P.S.; Herath, H.; Rajapakse, C.S.K.; Wijesinghe, P.; Attanayake, R.N.The involvement of wood decay fungi and the importance of their enzymes in polyethylene degradation is well documented. Therefore, decay-resistant hardwood associated fungi should be better degraders with their versatile enzymatic systems. In the current study, decaying hardwood associated fungi were isolated and their ability to degrade low-density polyethylene (LDPE) was assessed. Thirty-three isolates were identified by sequencing the internal transcribed spacer region of nuclear ribosomal DNA. Randomly selected isolates were tested for laccase producing abilities. Three species were selected to test their potentials in LDPE sheet degradation. Fungi were incubated in Czapek-Dox broth containing 20-micron LDPE sheets at room temperature for 60 days. The biodegradation signatures were assessed by analyzing the changes in structural characteristics of LDPE using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), percent reduction of tensile properties, and weight loss. FTIR analysis revealed changes in certain functional groups compared with the control, indicating chemical changes resulting from the treatment. LDPE sheets incubated with fungi showed cracks and holes under SEM analysis, percent reduction in tensile properties, and weight loss, which are the signatures of degradation. This study revealed that the hardwood decaying basidiomycetes, Phlebiopsis flavidoalba, Schizophyllum commune, and Phanerodontia chrysosporium have the potential for in vitro LDPE degradation.Item Antioxidant activity and chemical constituents of methanolic extract of Durio zibethinus Murr. (durian) peels(MEDICINAL PLANTS - INTERNATIONAL JOURNAL OF PHYTOMEDICINES AND RELATED INDUSTRIES, 2021) Perera, P.J.; Binuwangi, A.K.D.M.; Silva, A.A.G.; Attanayake, R.N.; Wickramarachchi, S.R.; Rajapakse, C.S.K.This study aimed to determine the DPPH free radical scavenging activity, total phenolic content (TPC) and total flavonoid content (TFC) of methanolic extract of Durio zibethinus Murr. (durian) peels and its fractions. The chemical constituents of durian peels extracted into methanol by soxhlet extraction were sequentially extracted into hexane, dichloromethane and aqueous methanol. Among the fractions, the dichloromethane fraction showed the highest DPPH free radical scavenging activity (IC50 179.9 ± 6.6 μg/ml) with high TPC and TFC (85.82 ± 12.11 mg gallic acid equivalent/g of dried weight of extract and 12.66 ± 1.94 mg of quercetin equivalent/g of dried weight of extract, respectively). A very strong positive correlation (r = 0.9677) was observed between the DPPH free radical scavenging activity and the TPC of fractions and a strong positive correlation (r = 0.7858) was noticed between the DPPH free radical scavenging activity and TFC of the fractions indicating that phenolic compounds in durian peels may contribute to their strong antioxidant activity. As the dichloromethane fraction had constituents with the highest antioxidant activity, it was analyzed by Gas chromatography-Mass spectrophotometry to identify its volatile constituents. The results revealed that the dichloromethane fraction was rich in [1,2-Benzenedicarboxylic acid, bis (2-ethylhexyl) ester], [2,3-diphenylquinoxaline], [2-coumaranone], [4-((1E)-3-hydroxy-1-propenyl)-2-methoxyphenol], [7,9-di-tert-butyl-1-oxaspiro (4,5) deca-6,9-diene-2,8-dione] and [phenol, 2,4-bis(1,1-dimethylethyl)], which are known to exhibit antioxidant activity.Item Removal of Fluoride from Drinking Water Using Protonated Glycerol Diglycidyl Ether Cross-Linked Chitosan Beads(Chem. Chem. Technol., 2021) Pathirannehe, P.; Rajapakse, C.S.K.; Fernando, T.D.In this study, physically and chemically modified chitosan; protonated glycerol diglycidyl ether cross-linked chitosan beads (GDCLCB/H+) were prepared and characterized using FTIR and SEM. The optimum defluoridation capacity (DC) of GDCLCB/H+ was observed at the initial F- ion concentration of 15 mg/l, adsorbent dosage of 0.6 g, contact time of 30 min and pH of the solution was in the range of 5–7 at 303 ± 2 K. The equilibrium adsorption data fitted well with Langmuir and Freundlich isotherm models. The maximum adsorption capacity (q0), obtained from Langmuir isotherm for F-adsorption was found to be 2000 mg/kg, which was significantly higher than that of unmodified chitosan (192.3 mg/kg) and most of the chitosan-based sorbents reported in the literature. Water samples collected from Medawachchiya, Sri Lanka, were treated with the adsorbents and the results suggested that GDCLCB/H+ could be used as an effective defluoridation agent.Item Exploration of antioxidant activity and photoprotective potential of methanolic extract of Ananas comosus (Pineapple) peel(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Samarakoon, S.M.G.K.; Rajapakse, C.S.K.Pineapple (Ananas comosus) is known to rich in phytochemicals with antioxidant and antimicrobial activities. As less research has been conducted to investigate the bioactivity of its peels, the present study aimed to evaluate the antioxidant activity and photo-protective property of methanolic extract of pineapple peel to investigate its potential to be used as a natural source of cosmeceutical sunscreen agents. Pineapples at full ripeness stage were purchased and the chemical constituents of dried and powdered pineapple peels (20.00 g) extracted into methanol by Soxhlet extraction were sequentially partitioned into hexane, dichloromethane and aqueous methanol (50%). The antioxidant activity of each fraction was determined by α-diphenyl- βpicrylhydrazyl (DPPH) free radical assay. Total phenolic content (TPC) and total flavonoid content (TFC) of methanolic extract and its fractions were assessed by Folin-Ciocalteu and aluminium chloride colorimetric assays respectively. The photo-protective potential of the fractions was evaluated by determining the Sun Protection Factor (SPF) of each fraction using the Mansur equation. All the tests were conducted in triplicates. The aqueous methanol fraction showed the highest DPPH free radical scavenging activity with IC50 value of 85.704 ± 0.09 µg/mL and the highest TPC of 41.780 ± 0.223 mg Gallic acid equivalent /g dry weight of plant material. Dichloromethane fraction was rich in flavonoids with TFC of 31.372 ± 0.996 mg Catechin equivalent/g dry weight of pineapple peel. All the fractions of methanolic extract of pineapple peel exhibited UV-B absorption and among them, dichloromethane fraction showed significantly high photo protective properties with an SPF of 29.74 ± 0.03 at 1 mg/mL while the SPF of the reference photo-protective agent, benzophenone was 13.75 ± 0.01 at 1 mg/mL. Aqueous methanol was found to be the most photo-stable after irradiation with direct solar radiation for 21 days. The results suggest that the extract of peels of pineapple could be incorporated into sunscreen formulation as a source rich in phytochemicals with potential antioxidant and photo-protective properties.Item Carbon Source dependent - anaerobic Soil Disinfestation (ASD) Mitigates the Sclerotial Germination of Sclerotinia Sclerotiorum(Tropical Plant Pathology (2020), 2020) Mahalingam, T.; Rajapakse, C.S.K.; Somachandra, K.P.; Attanayake, R.N.Though Sclerotinia sclerotiorum IS a well-studied plant pathogen that causes significant economic damage worldwide, sustain able and environmental friendly control methods are difficult to establish due to it wide host range, cosmopolitan distribution and production of recalcitrant structures that can survive in soil for a long time. The pathogen was found causing a severe disease incidence on cabbage in 2016 in Sri Lanka. It was hypothesized that a) isolates of the recent disease outbreak display cross resistance to commonly applied fungicides and b) carbon (C) source supplemented Anaerobic Soil Disinfestation (ASD) is effective in mitigating the germination of sclerotia. In vitro fungicide sensitivity assays showed large variation in mycelial growth inhibition indicating high adaptability of the population towards environmental fluctuations and management practices. Signatures of cross resistance were evident. ASD was carried out using cabbage (Brassica oleracea) and leek (Allium ampeloprasum) cull piles, durian (Durio zibethinus) peels and grass cuttings (Axonopus compressus) as C sources and determined the sclerotial viability. Cabbage and leek cull piles at rates of 60—100 mg/g soil completely inhibited sclerotial germination. Maintaining anaerobic condition along with C source amendments was found to be a critical step in mitigating the sclerotial germination. GC-MS analysis of the volatiles of cabbage leaves, leeks and durian further confirmed the presence of various bioactive compounds with potential antifungal activity. Therefore, in addition to elevated microbial activity in treatments, the volatiles of C sources may have helped mitigating sclerotial germination.Item Tea industry waste activated carbon as a low-cost adsorbent for methylene blue removal from wastewater(Research Journal of Chemical Sciences, 2018) Hettiarachchi, A.H.P.; Rajapakse, C.S.K.The possible utilization of tea industry waste activated carbon (TIWAC) as an inexpensive, eco-friendly bio adsorbent for methylene blue (MB) removal from wastewater was studied. Phosphoric acid was used as the activating agent for the preparation of TIWAC and Scanning Electron Microscopy and Fourier Transformed Infrared Spectroscopy were used to characterize TIWAC. In this work batch experiments were carried out at pH 7 and at temperature of 30±2 r to study the efficiency of MB adsorption on to TIWAC under different conditions such as TIWAC dosage, MB concentration, pH of the solution, and agitation time. The adsorption characteristics of the sorbent was tested with Freundlich and Langmuir adsorption models and the kinetic studies were conducted to determine the order of the adsorption process. The adsorption capacity of MB and the maximum % removal of MB by TIWAC were found to be 233.51 mg g and 77.8% respectively at the optimized adsorption conditions (TWAC dosage= 0.001 g, MB concentration= 300 mg/L, agitation time=6 hrs) at pH 7. Isotherm data were satisfied Langmuir model than Freundlich model and kinetic data were best fitted with the pseudo first order model. Most importantly, the Langmuir constant, the maximum adsorption capacity value (q0); obtained for adsorption of MB onto 77WAC was 303.3 mg g4 , which is significantly greater than that of the adsorption of MB by various other bio¬sorbents reported in the literature. Bench-scale fixed-bed column experiments were also carried out at various flow rates to study the practical usability of the adsorbent and it was found out that the breakthrough time was decreased with increasing flow rate. The results of this study indicate that TIWAC is an effective and environmental friendly adsorbent for removal of dye from wastewater.Item Phenotypic variation of cabbage white mold pathogen, Sclerotinia sclerotiorum in the upcountry commercial cabbage fields in Sri Lanka(Journal of the National Science Foundation of Sri Lanka 2018 46 (2): 159 – 164, DOI: http://dx.doi.org/10.4038/jnsfsr.v46i2.8416, 2018) Mahalingam, T.; Guruge, B.M.A.; Somachandra., K.P.; Jayasekara, E.A.E.S.S.; Rajapakse, C.S.K.; Attanayake, R.N.Sclerotinia sclerotiorum is a cosmopolitan, necrotrophic and soil borne plant pathogen, capable of infecting many economically important crops. Although it is a well-studied pathogen elsewhere, there is no research conducted in Sri Lanka. The objectives of the current research were to study the phenotypic variations among isolates within the pathogen population in the upcountry commercial cabbage fields in Sri Lanka and to determine their sensitivity to a commonly applied fungicide, Mancozeb. Forty-six isolates obtained from infected cabbage heads were identified as S. sclerotionun based on its unique morphological characteristics. Colony diameter was measured on potato dextrose agar (PDA) plates at 23 °C and mycelia' colour was observed after two-week incubation. All the isolates were grown in pH indicator media to determine their add producing abilities. Sensitivity of the isolates to Mancozeb was assayed in vitro. There was a significant difference in colony growth among the isolates and sensitivity to Mancozeb. Two isolates showed abnormal mycelia' growth characteristics; a slower growth rate on PDA and reduced pathogenicity on cabbage leaves. Two levels of mycelia' pigmentation were observed on PDA. All the isolates were acid producers, inferring that all of them were pathogenic. In summary, the upcountry S. sclerotiorton pathogen population was found to be diverse for selected phenotypic traits, especially for mycelia( growth, and fungicide sensitivities inferring that the pathogen population is capable of adapting to changing environmental conditions. Therefore, disease management will be challenging if an epidemic occurs, and it is recommended that a proper management system should be identified before further expansion of upcountry cabbage cultivation.Item Highly stable CuO incorporated TiO2 catalyst for photocatalytic hydrogen production from H2O(Journal of Photochemical & Photobiological Sciences, 2005) Bandara, J.; Udawatta, C.P.K.; Rajapakse, C.S.K.A CuO incorporated TiO2 catalyst was found to be an active photocatalyst for the reduction of H2O under sacrificial conditions. The catalytic activity originates from the photogeneration of excited electrons in the conduction bands of both TiO2 and CuO resulting in a build-up of excess electrons in the conduction band of CuO. Consequently, the accumulation of excess electrons in CuO causes a negative shift in the Fermi level of CuO. The efficient interparticle charge transfer leads to a higher catalytic activity and the formation of highly reduced states of TiO2/CuO, which are stable even under oxygen saturated condition. Negative shift in the Fermi level of CuO of the catalyst TiO2/CuO gains the required overvoltage necessary for efficient water reduction reaction. The function of CuO is to help the charge separation and to act as a water reduction site. The amount of CuO and crystalline structure were found to be crucial for the catalytic activity and the optimum CuO loading was ca. 5?10% (w/w).Item Synthesis, Characterization, and in vitro Antimalarial and Antitumor Activity of New Ruthenium(II) Complexes of Chloroquine(Journal of Inorganic Chemistry, 2009) Rajapakse, C.S.K.; Martínez, A.; Naoulou, B.; Jarzecki, A.A.; Suárez, L.; Deregnaucourt, C.; Sinou, V.; Schrével, J.; Musi, E.; Ambrosini, G.; Schwartz, G.K.; Sánchez-Delgado, R.A.The new RuII chloroquine complexes [Ru(?6-arene)(CQ)Cl2] (CQ = chloroquine; arene = p-cymene 1, benzene 2), [Ru(?6-p-cymene)(CQ)(H2O)2][BF4]2 (3), [Ru(?6-p-cymene)(CQ)(en)][PF6]2 (en = ethylenediamine) (4), and [Ru(?6-p-cymene)(?6-CQDP)][BF4]2 (5, CQDP = chloroquine diphosphate) have been synthesized and characterized by use of a combination of NMR and FTIR spectroscopy with DFT calculations. Each complex is formed as a single coordination isomer: In 1?4, chloroquine binds to ruthenium in the ?1-N mode through the quinoline nitrogen atom, whereas in 5 an unprecedented ?6 bonding through the carbocyclic ring is observed. 1, 2, 3, and 5 are active against CQ-resistant (Dd2, K1, and W2) and CQ-sensitive (FcB1, PFB, F32, and 3D7) malaria parasites (Plasmodium falciparum); importantly, the potency of these complexes against resistant parasites is consistently higher than that of the standard drug chloroquine diphosphate. 1 and 5 also inhibit the growth of colon cancer cells, independently of the p53 status and of liposarcoma tumor cell lines with the latter showing increased sensitivity, especially to 1 (IC50 8 ?M); this is significant because this type of tumor does not respond to currently employed chemotherapies