Judul: Kajian Metabolomik dan Density Functional Theory Terhadap Kapasitas Antioksidan Justicia gendarussa Pada Dosis Pupuk Nitrogen Berbeda
Abstrak: Justicia gendarussa, also known as gendarussa, is a plant that has the potential to be an antioxidant. J. gendarussa can grow wild as a bush, especially in forested settings and along river dams. These wild growth conditions will cause inconsistent secondary metabolite production and change biological activity, so it is necessary to cultivate J. gendarussa plants to maintain consistent secondary metabolite content. Plant cultivation treatments that can be carried out include different doses of nitrogen fertilizer. These metabolite changes can be observed using a metabolomics approach. Additionally, metabolomics can be used to identify active compounds. Then, to ensure the ability of the active compound, a computational density functional theory (DFT) chemistry study can be carried out. Therefore, this research aims to determine the optimal nitrogen fertilizer dose on J. gendarussa antioxidant capacity and metabolites using a metabolomics approach. Then, identify its antioxidant compounds in the J. gendarussa fraction with nitrogen fertilizer dose of the highest harvest weight using metabolomics and DFT. The research method begins with cultivating J. gendarussa plants at different doses of nitrogen fertilizer (0, 90, 180, 270 kg/ha), sample preparation, extraction, determination of extract antioxidant capacity, identification of extract metabolites, fractionation, determination of fraction antioxidant capacity, identification of fraction metabolites, DFT studies, and data analysis. The highest harvest weight with a mass of 11 g/plant was produced by plants given 270 kg/ha of nitrogen fertilizer. Antioxidant capacity was shown to be insignificantly different between treatments measured. Based on the metabolomics approach, variations in nitrogen fertilizer made metabolites at doses of 90 kg/ha and 180 kg/ha had higher relative concentrations of metabolites compared to doses of 270 kg/ha. So, 90 kg/ha are the optimal nitrogen fertilizer dose. The ethyl acetate and n-butanol fractions from the nitrogen fertilizer dose with the highest harvest weight had the highest antioxidant capacity. Principal component analysis (PCA) and heatmap succeeded in differentiating metabolites based on polarity. Orthogonal partial least square-discriminant analysis (OPLS-DA) succeeded in identifying six active compounds and 14 unknown compounds that had the potential to be isolated in the ethyl acetate fraction. DFT studies proves that 6-{[(Benzyloxy)carbonyl]amino}-6-deoxy-1,2-O-isopropylidene-alpha-D-glucofuranose and gendarusin A has a smaller gap energy than trolox standard, indicating its antioxidant activity is higher than trolox. Additional tests in vitro or in vivo research on the isolation results need to be carried out to prove the research results further.
Keyword: Cultivation, Gendarussa, Heatmap, PCA, OPLS-DA

Judul: Productivity of phenolic, flavonoid, and antioxidant of Justicia gendarussa at different shades and dose of nitrogen fertilizer
Abstrak: Penelitian ini bertujuan menentukan kombinasi naungan dan dosis pupuk nitrogen yang dapat menghasilkan produktivitas fenolik, flavonoid, dan antioksidan terbaik pada bagian aerial parts dari gandarusa (Justicia gendarussa). Rancangan split-plot digunakan pada penelitian ini dengan naungan (0, 25, dan 50%) sebagai petak utama dan dosis pupuk nitrogen (0, 90, 180, dan 270 kg/ha) sebagai anak petak. Hasil penelitian menunjukkan bahwa produktivitas fenolik, flavonoid, antioksidan, dan bobot kering tertinggi didapat pada perlakuan tanpa naungan dengan dosis pupuk nitrogen 270 kg/ha. Panen bobot kering tanaman mencapai 10,9 gram/tanaman. Produktivitas fenolik adalah 210 mg GAE/tanaman, sedangkan produktivitas flavonoid 112 mg QE/tanaman. Produktivitas antioksidan dengan metode DPPH, ABTS, FRAP, dan CUPRAC berturut-turut adalah 63,5; 334; 171; 525 µmol TE/tanaman. Analisis Pearson menunjukkan bahwa produktivitas fenolik dan flavonoid sangat berkolerasi kuat dengan produktivitas antioksidan. Tanpa naungan dengan dosis pupuk nitrogen 270 kg/ha merupakan kombinasi perlakuan budi daya paling tertinggi berdasarkan parameter penelitian, yaitu naungan dan dosis pupuk nitrogen berbeda., This study aims to determine the combination of shade and the dose of nitrogen fertilizer that can produce the best productivity of phenolic, flavonoid, and antioxidant of aerial parts of gandarusa (Justicia gendarussa). A split-plot design was used in this study with shade (0, 25, and 50%) as the main plot and nitrogen fertilizer doses (0, 90, 180, and 270 kg/ha) as subplots. The results showed the highest productivity of phenolics, flavonoids, antioxidants, and dry weight in the treatment without shading with a dose of 270 kg/ha of nitrogen fertilizer. The dry weight harvest of the plants was 10.9 g/plant. The phenolic productivity was 210 mg GAE/plant, while the productivity of flavonoids was 112 mg QE/plant. Antioxidant productivity using DPPH, ABTS, FRAP, and CUPRAC methods were 63.5; 334; 171; 525 µmol TE/plant, respectively. Pearson correlation shows that the productivity of phenolics and flavonoids is highly correlated with antioxidant productivity. Without shading and a dose of nitrogen fertilizer of 270 kg/ha was the best combination of cultivation treatments based on the research parameters based on shading and dose of nitrogen fertilizer.
Keyword: antioxidant, cultivation, flavonoids, Justicia gendarussa, phenolics

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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