Browsing by Author "Abeysinghe, T."

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Assessment of in vitro antioxidant activity and flavonoid content Vernonia cinerea
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Weerasinghe, P.; Abeysinghe, T.; Paranagama, P. A.
Leafy greens are an essential part of a healthy diet. Eating a diet rich in leafy greens can offer numerous health benefits including reduced risk of obesity, heart diseases, high blood pressure and mental decline. In Sri Lanka, Kola kanda or herbal porridge is a traditional breakfast made up of green leaves or herbs. Out of many herbs used for Kola kanda, Vernonia cinerea (Monarakudumbiya) is used to treat various diseases on folklore levels in Sri Lanka. However, no much scientific validation is found for V. cinerea for its medicinal uses. The present study was carried out to access the in vitro antioxidant activities and flavonoid content of leaf, root, stem and flower parts of V. cinerea. In vitro antioxidant potential of methanolic extracts of V. cinerea was evaluated by means of total phenolics by the Folin-Ciocalteu assay and the DPPH radical scavenging assay using standard procedures with slight modifications. The highest phenolic content of 101.80 ± 7.74 mg GAE/g was observed in flowers and the stem having the least phenolic content (71.95 ± 5.72 mg GAE/g). The flavonoid content ranged from 17.67 mg GAE/g to 12.76 mg GAE/g in all parts. DPPH radical scavenging activity of extracts of V. cinerea increased in a dose dependent manner with IC50 values ranging from 800 μg/mL to 2350 μg/mL in different parts. The leafy green, V. cinerea under this study contains a significant amount of essential phytochemicals which possess anti-oxidant properties supporting its use as a medicinal herb.
Comparative study on Proximate and Mineral composition in Vernonia cinerea
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Weerasinghe, P.; Abeysinghe, T.; Paranagama, P.A.
Vernonia cinerea is a herb having several medicinal properties such as antidiabetic, antioxidant, antimicrobial, antiinflammatory and anticarcenogenic. This work investigated the proximate and mineral composition in different parts (leaves, roots, stem and flowers) of V. cinerea using standard procedures. Collected data of proximate and mineral analysis were analyzed using one-way ANOVA. The results of the proximate composition were found to be as follows; ash content ranged between 10.00 ± 1.32 % w/w and 20.17 ± 6.74 % w/w while both leaves and roots had the highest and flower had the least ash content which was significantly different (P<0.05). The moisture content ranged between 61.24 ± 2.17 % - 75.45 ± 4.74 % w/w in the different parts of the plant. The mean nitrogen content ranged between 1.91 ± 0.23 % w/w and 4.80 ± 0.18 % w/w. The protein content in flower, leaf, stem and roots of V. cinerea were significantly different (P<0.05) and the values ranged between 9.19 ± 1.08 % w/w - 23.07 ± 0.85 % w/w %. The plant parts were also analyzed for mineral elements such as Zn and Cu metal ions using Atomic Absorption Spectroscopy (AAS). The levels of these elements found were; Zn:5.58 ± 0.14 - 51.27 ± 0.81 mg/kg and Cu 3.29 ± 0.06 - 8.57 ± 0.10 mg/kg with few exceptions. The mineral content of flower, roots, stem and leaves were significantly different (P<0.05). Therefore, V. cinerea as a therapeutically beneficial herb has a significant amount of proximate and mineral ion composition that can be specified.
Determination of narcotic (morphine, codeine, 6-monoacetylmorphine) levels in human urine by gas chromatoghraphy
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Manohari, I. D. M.; Karunaratne, W. D. V.; Abeysinghe, T.
Drug abuse has become a more prevalent problem in Sri Lanka in the last few years. The presence of residues and their metabolites of illicit drugs that are excreted by humans is an evidence of intake. Therefore, the aim of this study was to develop a selective and sensitive gas chromatography-mass spectrometry (GC-MS) method for the analysis of morphine, codeine, 6-monoacetylmorphine (6-MAM) in biological samples. Selected Ion Monitoring (SIM) mode of gas chromatography-mass spectroscopy was used to quantify morphine, codeine and 6-MAM in human urine samples. Derivatization was carried out after the liquid-liquid extraction of samples. The derivatization improved the sensitivity enabling the detection of codeine by 52% and morphine by 26%. For 6-MAM, recovery was greater than 45% compared to samples without derivatization. The linearity (r2) values of the methods were greater than 0.9976 for all the three analytes and the limits of quantifications were 2.22 g/mL, 2.22 g/mL and 2.14 g/mL for morphine, codeine and 6-MAM respectively These methods were applied to six urine samples collected from “Seth Sevana” Awareness and Rehabilitation Centre in Colombo. The samples were found to be containing 80-300 μg/mL of morphine and 219-439 μg /mL of codeine. However, the presence of 6-MAM in urine could not be identified due to possible rapid metabolization of 6-MAM, which addresses the lower recovery of the method for 6-MAM. The results indicate that this method can be used successfully for the determination of codeine and morphine levels in human urine, which thus can be used for rehabilitative purposes and to study drug addiction
Studies of Mass Modulated Enzymes with Purified Methylenetetrahydrofolate
(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Abeysinghe, T.; Kohen, A.
The potential of the folic acid biosynthesis pathway as a target for the development of antibiotics and chemotherapeutic drugs has been recognized for many years and validated by the clinical use. One function of folic acid metabolism is the support of DNA synthesis and repair through the generation of nucleic acid building blocks such as thymidine triphosphate (dTTP). This process involves the last step of de novo synthesis of a precursor of DNA, 2’- deoxythymidine-5’-monophosphate (dTMP) with thymidylate synthase (TSase EC 2.1.1.45) using the cofactor (6R)-N5,N10-methylene-5,6,7,8-tetrahydrofolate (CH2H4folate). Therefore, the isotopically labeled R-[6-xH]-CH2H4F (where xH: hydrogen, deuterium or tritium) allows studying the contribution of fast protein dynamics to a variety of kinetic steps along the catalytic cascade of natural vs. mass modulated Escherichia coli TSase. Ultimately, a better understanding of the catalytic mechanism of TSase can assist in developing more effective drugs that selectively act on cancerous cells therefore having reduced toxicity. Generally, HPLC remains as the main purification method of the synthesized R-[6-xH]-CH2H4F due to high sensitivity. However, it is quite laborious and the high salt content in the purified sample interferes with the NMR analysis. In this regard, we developed and optimized a simple procedure for the purification of the R-[6-DH]-CH2H4F (D= deuterium) after its synthesis using solid-phase extraction with a strong anion exchange (SAX) cartridge followed by a C-18 cartridge. The purified 6R-DH-CH2H4folate was used to investigate whether the mass modulation of the enzymes changes the rate-limiting step for the reaction. The kinetic studies indicated that the turnover number, kcat is no longer rate limited by the hydride transfer in mass modulated TSase chemical cascade.