Browsing by Author "Rajapakse, C.S.K."

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Adsorption of Chromium (III) from Aqueous Solutions Using Activated Carbon Derived from Wood Waste of Cinnamomum verum
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Samaraweera, I.D.H.T.; Rajapakse, C.S.K.
Contamination of water by heavy metals has readily increased as a result of urbanization and industrialization. Among the available techniques of contaminant removal, adsorption has widely been used for the removal of various pollutants including heavy metals from water. Therefore, the present study was conducted to investigate the potential of utilizing an agricultural waste, Cinnamomum verum wood waste, as a precursor for the production of low-cost activated carbon (AC) to use as an adsorbent for the removal of Cr (III) from aqueous solutions. First, the effect of carbonization time on production of AC derived from wood waste of Cinnamomum verum and their Cr (III) removal potential was evaluated to determine the optimum carbonization time for AC production. Cleaned and dried powdered wood waste samples (20.00 g) were carbonized at 400 °C for 30-120 minutes (30 min, 60 min, 90 min, 120 min) and chemically activated by H3PO4. The yield of AC samples prepared at different carbonization time and their Cr removal percentages (% Cr) at pH 7 and at room temperature (30 ± 2 0C) were determined. As the highest % Cr removal (~ 90 %) was observed for the AC prepared by carbonization of wood waste at 400 °C for 60 minutes with H 3PO 4 activation, AC prepared under the given conditions were selected for batch adsorption and isotherm studies. The surface morphology and the elemental composition of the novel adsorbent was examined by Scanning Electron Microscopy & Energy Dispersive Spectroscopy (SEM/EDS). Further, the adsorbent was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and proximate analysis. The effect of initial Cr (III) concentration (1.00, 3.00, 5.00, 8.00, 9.00, 12.00 mg/L), shaking time (30, 60, 90, 120,150,180 min) and adsorbent dosage (0.05, 0.25, 0.50, 0.75, 1.00, 1.25 g) on adsorption of Cr onto AC was then investigated by conducting batch experiments at pH 7 and at room temperature (30 ± 2 0C). According to the results the highest % Cr removal of 92.5% was obtained at initial Cr (III) concentration of 2.00 mg L-1, shaking time of 120 minutes and at adsorbent dosage of 0.05 g. The equilibrium data for the adsorption of Cr (III) on the AC derived from wood waste were tested with two adsorption isotherm models namely Freundlich isotherm and Langmuir isotherm and the results showed that the equilibrium data were better represented by the Langmuir isotherm model (R² = 0.998) with the maximum Cr adsorption capacity (q0) of 10.75 mg g −1. Therefore, the results of the study revealed that the AC derived from wood waste of Cinnamomum verum could be considered as a promising and environmentally friendly novel adsorbent for the removal of Cr from aqueous solutions including wastewater.
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.
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.
Arene–Ru(II)–chloroquine complexes interact with DNA, induce apoptosis on human lymphoid cell lines and display low toxicity to normal mammalian cells
(Journal of Inorganic Biochemistry, 2010) Martínez, A.; Rajapakse, C.S.K.; Sánchez-Delgado, R.A.; Varela-Ramirez, A.; Lema, C.; Aguilera, R.J.
The complexes [Ru(?6-p-cymene)(CQ)Cl2] (1), [Ru(?6-benzene)(CQ)Cl2] (2), [Ru(?6-p-cymene)(CQ)(H2O)2][BF4]2 (3), [Ru(?6-p-cymene)(en)(CQ)][PF6]2 (4), [Ru(?6-p-cymene)(?6-CQDP)][BF4]2 (5) (CQ = chloroquine base; CQDP = chloroquine diphosphate; en = ethylenediamine) interact with DNA to a comparable extent to that of CQ and in analogous intercalative manner with no evidence for any direct contribution of the metal, as shown by spectrophotometric and fluorimetric titrations, thermal denaturation measurements, circular dichroism spectroscopy and electrophoresis mobility shift assays. Complexes 1?5 induced cytotoxicity in Jurkat and SUP-T1 cancer cells primarily via apoptosis. Despite the similarities in the DNA binding behavior of complexes 1?5 with those of CQ the antitumor properties of the metal drugs do not correlate with those of CQ, indicating that DNA is not the principal target in the mechanism of cytotoxicity of these compounds. Importantly, the Ru?CQ complexes are generally less toxic toward normal mouse splenocytes and human foreskin fibroblast cells than the standard antimalarial drug CQDP and therefore this type of compound shows promise for drug development.
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.
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.
Determination of metal content in Rasna Sapthaka Kwatha
(Young Ayurveda Researchers' and Innovators' Symposium (YARIS – 2019), Institutional Research Committee, Gampaha Wickramarachchi Ayurveda Institute, University of Kelaniya, Yakkala, Sri Lanka, 2019) Abeysingha, W.A.M.U.S.; Nilmini, R.R.P.S.; Rajapakse, C.S.K.; Weerasooriya, W.M.B.
Rasna sapthaka kwatha is a widely used Ayurvedic decoction. Medicinal plants that are the ingredients of this decoction are collected from different habitats of the country. The decoction can be contaminated with metals during the growing, collecting, and storing of the raw material and also during the processing of this product. Hence, the evaluation of metal concentration in pharmaceutically available decoction is of utmost significance. Therefore, the main objective of this research was to determine the concentration of Al, Cr, Cd, Cu, and Pb in decoction samples of Rasna sapthaka kwatha collected from different areas of Sri Lanka. Ten samples of decoction were randomly collected from Anuradhapura, Kurunegala, Kandy, Polonnaruwa, Thambuththegama, Galadiulwewa and Gampaha. Atomic Absorption Spectrometry was used to detect the metal concentration. Wet digestion was carried out prior to the analysis. The mean concentration value of Al, Cd, Cr and Cu were 1.010ppm, 0.232 ppm, 0.387 ppm and 0.155 ppm respectively. Pb was below the detected level of the instrument. Al, Cd, Cr and Cu contents in decoction samples were found in the range of 0.39-2.208 ppm, 0.18-0.348 ppm, 0.33-0.462 ppm, and 0.042-0.408 ppm respectively. Results revealed that the mean values of metal concentration of tested samples were below the recorded WHO permissible level of metals in herbal medicine.
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.
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).
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.
Preparation, Characterization and Evaluation of Lead Adsorption Efficiency of Chitosan Coated Activated Carbon
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Perera, P.L.R.A.; Rajapakse, C.S.K.
Heavy metal contamination in various water resources is of great concern because of the toxic effect on human beings and other animals and plants in the environment. Lead is a major element which is released to the environment including water bodies by many industries and it is well known that the presence of Pb(II) in water, even at very low concentrations, is extremely harmful to the human. Therefore, the aim of the present study was to investigate the Pb adsorption potential of chitosan coated activated carbon derived from rice husk (CCAC) in aqueous media. First, chitin was extracted from shrimp shell wastes by following a standard procedure and it was deacetylated to obtain chitosan (deacetylation percentage = 82%). In the preparation of activated carbon from rice husk, HCl acid (5 % v/v) was used as the activating agent. The adsorbent of the study, CCAC was then prepared by coating activated carbon derived from rice husk (20.00 g) with chitosan (3.00 g dissolved in 1% v/v acetic acid) to improve the stability and mechanical strength of chitosan. The surface morphology and the elemental composition of CCAC was examined by Scanning Electron Microscopy & Energy Dispersive Spectroscopy (SEM/EDAX). The novel adsorbent was further characterized by Fourier Transform Infrared Spectroscopy (FT-IR). In order to determine the Pb adsorption potential of CCAC, batch adsorption studies were conducted at room temperature at pH 7. The effects of various experimental parameters such as initial Pb (II) concentration, dose of adsorbent and shaking time on Pb adsorption to CCAC were evaluated. According to the results, the maximum lead removal percentage (89%) was observed at initial Pb (II) concentration of 2 ppm, adsorbent dosage of 1 g/L and 120 minutes of shaking time. Further, the equilibrium adsorption data were analyzed by the Langmuir isotherm model and the Freundlich isotherm model for Pb adsorption onto CCAC. Among the two models, Langmuir isotherm best fitted with the equilibrium data (R2= 0.9916) with a maximum adsorption capacity (q0) of 24.39 mg/g. Based on the results, it can be concluded that CCAC can be considered as an efficient and cost-effective adsorbent for the removal of heavy metals such as Pb from industrial wastewater.
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.
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
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.
The antimalarial activity of Ru?chloroquine complexes against resistant Plasmodium falciparum is related to lipophilicity, basicity, and heme aggregation inhibition ability near water/n-octanol interfaces
(Journal of Biological Inorganic Chemistry, 2009) Martínez, A.; Rajapakse, C.S.K.; Jalloh, D.; Dautriche, C.; Sánchez-Delgado, R.A.
We have measured water/n-octanol partition coefficients, pK a values, heme binding constants, and heme aggregation inhibition activity of a series of ruthenium??-arene?chloroquine (CQ) complexes recently reported to be active against CQ-resistant strains of Plasmodium falciparum. Measurements of heme aggregation inhibition activity of the metal complexes near water/n-octanol interfaces qualitatively predict their superior antiplasmodial action against resistant parasites, in relation to CQ; we conclude that this modified method may be a better predictor of antimalarial potency than standard tests in aqueous acidic buffer. Some interesting tendencies emerge from our data, indicating that the antiplasmodial activity is related to a balance of effects associated with the lipophilicity, basicity, and structural details of the compounds studied.
The mechanism of antimalarial action of the ruthenium(II)?chloroquine complex [RuCl2(CQ)]2
(Journal of Biological Inorganic Chemistry, 2008) Martínez, A.; Rajapakse, C.S.K.; Naoulou, B.; Kopkalli, Y.; Davenport, L.; Sánchez-Delgado, R.A.
The mechanism of antimalarial action of the ruthenium?chloroquine complex [RuCl2(CQ)]2 (1), previously shown by us to be active in vitro against CQ-resistant strains of Plasmodium falciparum and in vivo against P. berghei, has been investigated. The complex is rapidly hydrolyzed in aqueous solution to [RuCl(OH2)3(CQ)]2[Cl]2, which is probably the active species. This compound binds to hematin in solution and inhibits aggregation to ?-hematin at pH ? 5 to a slightly lower extent than chloroquine diphosphate; more importantly, the heme aggregation inhibition activity of complex 1 is significantly higher than that of CQ when measured at the interface of n-octanol?aqueous acetate buffer mixtures under acidic conditions modeling the food vacuole of the parasite. Partition coefficient measurements confirmed that complex 1 is considerably more lipophilic than CQ in n-octanol?water mixtures at pH ? 5. This suggests that the principal target of complex 1 is the heme aggregation process, which has recently been reported to be fast and spontaneous at or near water?lipid interfaces. The enhanced antimalarial activity of complex 1 is thus probably due to a higher effective concentration of the drug at or near the interface compared with that of CQ, which accumulates strongly in the aqueous regions of the vacuole under those conditions. Furthermore, the activity of complex 1 against CQ-resistant strains of P. falciparum is probably related to its greater lipophilicity, in line with previous reports indicating a lowered ability of the mutated transmembrane transporter PfCRT to promote the efflux of highly lipophilic drugs. The metal complex also interacts with DNA by intercalation, to a comparable extent and in a similar manner to uncomplexed CQ and therefore DNA binding does not appear to be an important part of the mechanism of antimalarial action in this case.