Browsing by Author "Karunasiri, M. G. A. N."

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IDENTIFICATION AND QUANTIFICATION OF PREVIOUSLY UNEXPLORED CHEMICAL AND NUTRITIONAL INFORMATION ABOUT COCONUT CAKE
(2019) Karunasiri, M. G. A. N.
Coconut cake (CC) is the by-product of coconut oil manufacturing process which is rich in antioxidants. There is very little information on the antioxidant activity of CC in biological systems. In this study, the correlation of antioxidant activity of CC with biological and chemical systems was monitored. Ethanol: water 70: 30 (v/v) was used to extract phenolic compounds and that extract is denoted as CCPE. The total phenolic content was 1892±51 GAE mg/kg dry weight and o-diphenol content was 591±48 CAE/kg dry weight. The percentage of ferric reducing power and DPPH radical scavenging activity of CCPE increased with increasing concentrations. Those antioxidant activities are comparable to gallic acid (GA). HPLC system was used to identify and quantify the total polyphenols present in CCPE. GA is the prominent polyphenol compound while syringic acid is the least abundant. The effect of CCPE on deoxyribose degradation and protein carbonylation showed comparable antioxidant activity to GA. Further, CCPE has the ability to prevent DNA damage in -vitro. HEp- 2 human epithelial cells were used as the biological system to measure the antioxidant activity of CCPE. CCPE significantly (P≤0.05) inhibited MDA formation, protein carbonyl formation and mt-DNA damage in HEp-2 cells. The amount of oxidized glutathione decreased resulting in a significantly (P≤0.05) increased GSH/GSSG ratio upon treatment with CCPE. Further, CCPE resulted in no significant change in GPx expression compared to the unstressed cells. Therefore, CCPE can inhibit oxidative stress-induced macromolecular damage on carbohydrate, protein, lipid and DNA in both chemical and biological systems and the protective effect does not appear to result from a change in the level of expression in the oxidative stress response genes.
Protective Effect of Coconut Cake Phenolic Antioxidants on Oxidative Stress Induced Macromolecular Damage in HEp-2 Cells.
(In: Proceedings of the International Postgraduate Research Conference 2017 (IPRC – 2017), Faculty of Graduate Studies, University of Kelaniya, Sri Lanka., 2017) Karunasiri, M. G. A. N.; Seneviratne, K.N.; Jayathilaka, N.
Coconut cake, a by-product of the coconut oil manufacturing is a rich source of phenolic antioxidants. The majority of research dealing with phenolic antioxidants is primarily focused on the extraction of phenolic substances from plant materials and assessment of antioxidant properties in chemical systems. However, such assays in chemical systems do not guarantee the antioxidant properties of phenolic substances in biological systems. In this study, inhibition of H2O2 induced oxidative damage on lipids and proteins by coconut cake phenolic antioxidants (CCPA) was studied in HEp-2 cells as the biological system. CCPA were extracted with 70 % ethanol and the total polyphenol content was measured by Folin Ciocalteu method. The CCPA content, calculated as gallic acid equivalents was 182.81 ± 28.73 mg/kg. The o-diphenols content, calculated as caffeic acid equivalent using a method reported by Gutfinger was 66.83 ± 16.50 mg/kg. Oxidative damage in HEp-2 cells was induced by adding H2O2in PBS for 1 hr. The maximum concentration of H2O2 that does not affect the cell viability (>99 %) was determined as 100 µM using Cell-Titer Glo Luminescent Cell Viability Assay. Formationof thiobarbituric acid reactive species (TBARS) due to lipid peroxidationin HEp-2 cells (0.010±0.000 µM/mL) compared to the control (0.007±0.000 µM/mL) without H2O2was inhibited with 0.5mg/mLCCPA (0.007±0.000µM/mL). Protein oxidation (3.05±0.06nmol/mL) compared to the control (2.14±0.06nmol/mL) without H2O2 as assessed by protein carbonyl formation assay with 2, 4-dinitophenylhydrazine was alsoinhibited by treating the HEp-2 cells with 0.5mg/mL CCPA (2.41±0.06 nmol/mL). Thus, CCPA caninhibit oxidative stress-induced macromolecular damage of lipids and proteins in biological systems.