Browsing by Author "Seneviratne, K."

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Antioxidant Effect of Coconut Milk on Oxidative Damage in Commensal Lactobacilli in the Gastrointestinal Tract
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Karunasiri, A.N.; Gunawardena, M.; Seneviratne, K.; Jayathilaka, N.
Coconut milk (CM) is the aqueous extract of coconut endosperm which is rich in polyphenols. Coconut milk is commonly used in culinary applications in South Asia. In this study, protective effect of phenolic antioxidants (PA) extracted from CM was tested in lactobacilli which are the prominent probiotic forms in the human gut. These commensals help to maintain the immune and metabolic homeostasis. The intestinal environment can be altered by many factors that generate reactive oxygen species (ROS) resulting in oxidative stress. Enteric bacteria have been reported to mediate redox homeostasis through the regulation of ROS production. However, oxidative damage to the gut microbiota has been suggested to contribute to several diseases including intestinal and neurodegenerative disorders. Here, the activity of phenolic antioxidants extracted from CM on oxidative damage in Lactobacillus acedophillus, L. plantarum, L. lactis, L. casei and L. fermentum under aerobic conditions were evaluated based on the amount of products of macromolecular damage. The total polyphenol content of aqueous extract of CM was 8.21±0.13 mg/L as determined by the Folin Ciocalteu method. Bacterial cultures at optical density of 0.5 at 620 nm were incubated at 37°C under aerobic conditions to induce the oxidative damage. The cells were cultured overnight with a concentration series of PA (0, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9 mg/mL) to assess the protective effect on oxidative damage. The concentration of PA was kept below the concentration that affect cell viability as determined by 2,3,5-triphenyltetrazolium chloride assay at 620 nm. Lipid peroxide levels (μg/mL) and protein carbonyl levels (nmol/mL) were detected with thiobarbituric acid and 2,4-DNPH respectively. Growth under aerobic conditions affected the cell viability and induced significant (P<0.05) damage to proteins and lipids in the lactobacilli under investigation. Treatment with increasing concentrations of PA from CM showed a corresponding increase in the cell viability and a corresponding decrease in the amount of lipid peroxides and protein carbonyls under aerobic conditions. Therefore, PA from CM protect gut microbiota from oxidative damages in lipid and proteins without affecting their viability.
Cross-sectional study to assess risk factorsfor leishmaniasis in an endemic region in Sri Lanka
(American Society of Tropical Medicine and Hygiene, 2013) Ranasinghe, S.; Wickremasinghe, R*.; Munasinghe, A.; Hulangamuwa, S.; Sivanantharajah, S.; Seneviratne, K.; Bandara, S.; Athauda, I.; Navaratne, C.; Silva, O.; Wackwella, H.; Matlashewski, G.; Wickremasinghe, R.
Sri Lanka reports significantly more cutaneous leishmaniasis (CL) cases than visceral leishmaniasis (VL) cases, both of which are caused by Leishmania donovani MON-37. A cross-sectional study conducted in an area with a high prevalence of CL prevalent included 954 participants of an estimated population of 61,674 to estimate the number of CL cases, ascertain whether there is a pool of asymptomatic VL cases, and identify risk factors for transmission. A total of 31 cases of CL were identified, of whom 21 were previously diagnosed and 10 were new cases. Using rK39 rapid diagnostic test to detect antibodies against Leishmania spp., we found that only one person was seropositive but did not have clinical symptoms of CL or VL, which indicated low transmission of VL in this area. χ(2) test, independent sample t-test, and multivariate analysis of socio demographic and spatial distribution of environmental risk factors showed that living near paddy fields is associated with increased risk for transmission of CL (P ≤ 0.01).
Determination of Antioxidant and Antimicrobial Activities of Psidium guineense Sw. Leaf Extracts Fractioned Based on Polarity
(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Munaweera, R.R.K.W.; Senanayake, C.; Algama, H.; Seneviratne, K.; Jayathilaka, N.
Psidium guineense Sw. is a guava species distributed in South America, some parts of Africa and South Asia including Sri Lanka. Our previous studies have shown that Psidium guineense Sw. leaves contain 195.25±9.56 mg g-1 phenolic substances and 70 % ethanolic extract of P. guineense Sw. Leaves (PGLE) improve the oxidative stability and microbial shelf life of vanilla cake. PGLE may contain highly polar as well as medium and low polar phenolic substances. Therefore, antioxidant activity and antimicrobial activity of the further fractionated portions by chloroform and hexane of PGLE on food spoilage bacteria were determined. For this purpose, PGLE was obtained by solvent extraction and solvents of PGLE and different fractions were evaporated and reconstituted in 10 % ethanol. The antioxidant activities of solvent fractions, BHT and PGLE measured using DPPH radical scavenging assay are given in Figure 1. Figure 1. DPPH radical scavenging activity The antimicrobial activities of PGLE, chloroform fraction of PGLE and hexane fraction of PGLE were determined using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay for four microbial strains, two gram negative; Escherichia coli and Salmonella typhimurium and two gram positive; Bacillus cereus and Staphylococcus aureus. Ethanol from the extracts was maintained at 1% in the antimicrobial assays. PGLE showed the higher antimicrobial activity towards gram positive bacteria with LD50 values of 190.4 ± 20.2 mg/L for Staphylococcus aureus and 305.4 ± 22.4 mg/L for Bacillus cereus than gram negative bacteria with LD50 of 444.9 ± 13.0 mg/L for Escherichia coli and 508.6 ± 64.7 mg/L for Salmonella typhi. Streptomycin and chloramphenicol were used as positive controls. No antimicrobial activity was observed for chloroform and hexane fractions of PGLE in the four bacterial strains tested. The results of the present study suggest that phenolic compounds with medium polarity may be mainly responsible for antioxidant activity while phenolic compounds with high polarity may be responsible for antimicrobial activity.
Intelligent Window Controlling System
(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Seneviratne, K.; Jayatissa, N.W.K.
During the 21st century the global surface temperature has increased dramatically as a result of that, Air conditioners are often used to improve thermal comfort and indoor air quality. In both developed and developing countries, air conditioners increase the occupancy ratio of building areas. But air conditioners are expensive option for this issue. Because of that we need to optimize usage of air conditioners only in comfort zone. This research is conducted due to the growing energy management interest in the airconditioning industry. Most of the places outside air temperature and humidity drop down to human comfort levels during the night time. It may take considerable time to transfer these environmental conditions into the room. Insulated thermal envelope may be slowing this process furthermore. The objective of this research was to transfer the fresh outside air into the air conditioned room when the outside environment is in the comfort zone. Comfort zone is an area marked in the psychrometric chart which is comfortable for human being. The American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE’s) publication on thermal environmental conditions for human occupancy has defined the comfort zone with suitable temperature and relative humidity (RH) ranges. The specified temperature and humidity ranges for the designed system are 22 Celsius & 40 RH to 27 Celsius & 60 RH respectively. The designed controller detects the outside temperature and relative humidity every 15 minutes and opens the windows of the room if the outside fall into comfort zone. When the windows are opened the air conditioner is switched off by the controller at the same time. The designed system consists of three separate items such as outdoor unit, indoor unit and actuator driver. Relative humidity and temperature of the outside air are measured and transmitted to the room via radio frequency (RF) communication system by the outdoor unit. The indoor unit receives the transmitted signal from the outdoor unit, process it and produce appropriate signals to both actuator driver and air conditioner. Therefore, actuator driver is controlled the window according to the outside environmental conditions. The designed system is commissioned in Thailand and it is proven that the device is significantly saving the energy in the residential sector.
Phenolic antioxidants in coconut oil: Factors affecting the quantity and quality. A review
(Grasas Y Aceites, 2022) Jayathilaka, N.; Seneviratne, K.
The total phenol content (TPC) in coconut oil varies with extraction method, variety, nature of coconut kernel components and geographical origin. Commonly reported TPCs of coconut oils extracted by dry methods and wet methods are in the range of 70-300 mg/kg and 250-650 mg/kg, respectively. Based on the commonly reported data, the TPC of coconut oil varies by up to 527 mg/kg oil, 180 mg/kg oil, and 172 mg/kg oil due to the influence of the extraction method, coconut variety and the nature of kernel components, respectively. The identity of the phenolic compounds also varies with the extraction method. Caffeic acid, catechin, p-coumaric acid, ferulic acid, and syringic acid are present in different quantities in coconut oil when extracted by all methods. However, chlorogenic acid, cinnamic acid, epigallocatechin, gallic acid, vanillic and epicatechin are present only in some coconut oils. Many free phenolic compounds present in olive oil are also present in coconut oil.