Artik Elisa Angkawijaya

Bio: Artik Elisa Angkawijaya is an academic researcher from National Taiwan University of Science and Technology. The author has contributed to research in topics: Adsorption & Aqueous solution. The author has an hindex of 12, co-authored 68 publications receiving 1252 citations. Previous affiliations of Artik Elisa Angkawijaya include Academia Sinica.

Iron(III), Chromium(III), and Copper(II) Complexes of l-Norvaline and Ferulic Acid

Abstract: The complexation equilibria of l-norvaline (Nva) and ferulic acid (FA) were studied in aqueous solutions at room temperature (298 K) and in fixed ionic strength (0.15 mol·dm−3 NaNO3) by means of potentiometry and spectrophotometry techniques. The ferric (Fe3+), chromium (Cr3+), and cupric (Cu2+) complexing capacities of Nva and FA and their overall stability constants in aqueous solutions were obtained by the HYPERQUAD 2008 program from the potentiometric data. The concentration distributions of the various complex specia in solution were evaluated and discussed. The spectroscopic UV−visible measurements are carried out to give qualitative information about the confirmation of the complexes formed in these solutions.

Carbon microsphere from water hyacinth for supercapacitor electrode

Abstract: In this study, water hyacinth was hydrolyzed to sugars with dilute sulphuric acid (0.25 M) under subcritical water conditions (P = 20 bar, T = 130 °C) for 2 h. The sugar solution was then carbonized under subcritical conditions to produce carbon microsphere. The subcritical water carbonization was conducted at 40 bar and various temperatures (160–200 °C) and times (6–10 h). The highest yield of carbon microspheres was 0.1019 g/g dry water hyacinth at the temperature of 200 °C for 10 h. The carbon microsphere was activated using a combination of chemical (KOH solution) and physical (microwave) treatments to increase the specific surface area and porosity of carbon microsphere. Electrocapacitive study of carbon microspheres showed that the carbon microsphere activated at impregnation ratio of 1:1 and microwave power of 630 W has the highest specific capacitance and excellent electrochemical stability.

Cu(II), Co(II), and Ni(II)–Antioxidative Phenolate–Glycine Peptide Systems: An Insight into Its Equilibrium Solution Study

Abstract: The stability of complex formation between divalent transition metal ions, phenolates and glycine peptides was studied at 298.15 K in aqueous solution with an ionic strength of 0.15 mol·dm–3 NaNO3. HYPERQUAD 2008, a program based on nonlinear least-squares curve fitting, was used to determine the stability constants of the complexes formed from the pH-potentiometric data. The trends in stability constants of the complexes and the contribution of deprotonated or undeptotonated amide peptide in the stability constant were discussed. From the stability constants that obtained, the representative species distribution diagrams of copper complexes were provided by the HYSS 2009 program. In addition, structures of the formed complexes were predicted by using the Gaussian 09 program. The Gibbs free energies of these complexes were also evaluated in the simulation.

Antioxidants of Natural Plant Origins: From Sources to Food Industry Applications.

Abstract: In recent years, great interest has been focused on using natural antioxidants in food products, due to studies indicating possible adverse effects that may be related to the consumption of synthetic antioxidants. A variety of plant materials are known to be natural sources of antioxidants, such as herbs, spices, seeds, fruits and vegetables. The interest in these natural components is not only due to their biological value, but also to their economic impact, as most of them may be extracted from food by-products and under-exploited plant species. This article provides an overview of current knowledge on natural antioxidants: their sources, extraction methods and stabilization processes. In addition, recent studies on their applications in the food industry are also addressed; namely, as preservatives in different food products and in active films for packaging purposes and edible coatings.

A review on the current status of various hydrothermal technologies on biomass feedstock

Abstract: Hydrothermal processing, a thermochemical approach, is an excellent method of converting energy-rich biomass into useful products. This approach offers the advantage of handling biomass with relatively high moisture content by precluding an energy-intensive pretreatment step. Hydrothermal processing is of world-wide interest in view of depleting fossil-fuel reserves and increased environmental greenhouse gas emissions. There is potential to develop this novel technology at demonstration scale. This paper reviews the three hydrothermal technologies, namely hydrothermal liquefaction, gasification and carbonization, to provide insight into the likelihood of commercialization. The study discusses the role of different process parameters that have key impacts on the quality and yield of the desired products. This study also identifies the gaps in the literature including the need to establish a baseline to develop key process models and to perform a techno-economic assessment to get a better sense of the viability of the technology in future.

Evaluation of the Use of Different Solvents for Phytochemical Constituents, Antioxidants, and In Vitro Anti-Inflammatory Activities of Severinia buxifolia

Abstract: Severinia buxifolia (Rutaceae) is a promising source of bioactive compounds since it has been traditionally used for the treatment of various diseases. The present study aimed at evaluating the impact of different solvents on extraction yields, phytochemical constituents and antioxidants, and in vitro anti-inflammatory activities of S. buxifolia. The results showed that the used solvents took an important role in the yield of extraction, the content of chemical components, and the tested biological activities. Methanol was identified as the most effective solvent for the extraction, resulting in the highest extraction yield (33.2%) as well as the highest content of phenolic (13.36 mg GAE/g DW), flavonoid (1.92 mg QE/g DW), alkaloid (1.40 mg AE/g DW), and terpenoids (1.25%, w/w). The extract obtained from methanol exhibited high capacity of antioxidant (IC50 value of 16.99 μg/mL) and in vitro anti-inflammatory activity (i.e., albumin denaturation: IC50 = 28.86 μg/mL; antiproteinase activity: IC50 = 414.29 μg/mL; and membrane stabilization: IC50 = 319 μg/mL). The antioxidant activity of the S. buxifolia extract was found to be 3-fold higher than ascorbic acid, and the anti-inflammatory activity of S. buxifolia extract was comparable to aspirin. Therefore, methanol is recommended as the optimal solvent to obtain high content of phytochemical constituents as well as high antioxidants and in vitro anti-inflammatory constituents from the branches of S. buxifolia for utilization in pharmacognosy.