Judul: Variasi Aksesi terhadap Total Fenolik, Flavonoid serta Aktivitas Antioksidan Daun Gandarusa Asal Indonesia
Abstrak: Gandarusa (Justicia gendarussa Burm. f.) merupakan tanaman obat yang memiliki kandungan metabolit sekunder sebagai antioksidan. Produksi metabolit sekunder tanaman dipengaruhi oleh banyak faktor salah satunya variasi aksesi. Penelitian ini bertujuan memperoleh aksesi terbaik gandarusa yang menghasilkan metabolit sekunder dan aktivitas antioksidan tertinggi. Ekstrak etil asetat daun gandarusa diukur kadar total fenoliknya dengan metode Folin-Ciocalteu, kadar total flavonoid dengan metode aluminium klorida, serta aktivitas antioksidan dengan metode FRAP (Ferric Reducing Antioxidant Power) dan DPPH (1,1-diphenyl-2-picrylhydrazyl). Aksesi Langkat menghasilkan kadar total fenolik tertinggi sedangkan aksesi Malang menghasilkan kadar total flavonoid tertinggi yang berturut-turut sebesar 12,048 mg GAE g-1 bobot kering dan 17,043 mg QE g-1 bobot kering. Aksesi Bekasi menghasilkan aktivitas antioksidan FRAP tertinggi sedangkan aksesi Langkat menghasilkan aktivitas antioksidan DPPH tertinggi dengan nilai berturut-turut 16,669 dan 0,257 μmol TE g-1 bobot kering. Adapun korelasi antar variabel tidak menunjukkan hasil yang signifikan., Gandarusa (Justicia gendarussa Burm. f.) is a medicinal plant that contains secondary metabolites as antioxidants. The production of secondary metabolites of plants is influenced by many factors, one of which is the variation in accession. This study aimed to obtain the best accession of gandarusa which produces secondary metabolites and the highest antioxidant activity. Ethyl acetate extract of gandarusa leaves measured its total phenolic levels by the Folin-Ciocalteu method, total flavonoid levels with the aluminum chloride method, as well as antioxidant activity with the FRAP and DPPH methods. The Langkat accession produced the highest total phenolic levels while the Malang accession produced the highest total flavonoid levels which were successively 12,048 mg GAE g-1 dry weight and 17,043 mg QE g-1 dry weight. The Bekasi accession produced the highest FRAP antioxidant activity while the Langkat accession produced the highest DPPH antioxidant activity with successive values of 16.669 and 0.257 μmol TE g-1 dry weight. As for the correlation between variables, it does not show any significant results.
Keyword: accession, antioxidant, flavonoid, Justicia gendarussa, phenolic

Judul: Analysis of Total Phenolics, Flavonoids, and Antioxidant Activities in Ethanol Extracts of Three Accessions Gandarusa
Abstrak: Perbedaan aksesi dapat mempengaruhi kandungan fenolik, flavonoid, dan aktivitas antioksidan pada tanaman obat seperti gandarusa. Penelitian ini bertujuan mengukur dan menentukan kadar total fenolik, kadar total flavonoid, dan aktivitas antioksidan tertinggi pada ekstrak etanol daun gandarusa aksesi Langkat, Malang, dan Bekasi. Sampel diekstraksi dengan metode sonikasi dan maserasi. Kadar total fenolik diukur dengan metode Follin-Ciocalteu, flavonoid dengan metode AlCl3, dan aktivitas antioksidan dengan dua metode, yakni FRAP dan DPPH. Hasil menunjukkan bahwa kadar total fenolik, total flavonoid, dan aktivitas antioksidan metode DPPH tertinggi diperoleh pada aksesi Langkat. Aktivitas antioksidan metode FRAP tertinggi diperoleh pada gandarusa aksesi Malang. Kadar total fenolik memiliki korelasi tidak signifikan terhadap aktivitas antioksidan secara statistik. Sementara kadar total flavonoid berkorelasi signifikan dan sangat kuat terhadap aktivitas antioksidan DPPH, namun tidak pada metode FRAP. Aksesi gandarusa terbaik merupakan Langkat., Differences in accession can affect the content of phenolic, flavonoid, and antioxidant activity in medicinal plants such as gandarusa. This reasearch was aimed to measure and determine the total phenolic content, total flavonoid content, and the highest antioxidant activity in ethanol extract of gandarusa leaf accession of Langkat, Malang, and Bekasi. Samples were extracted by sonication and maceration methods. Total phenolic content was measured by the Follin-Ciocalteu method, flavonoids by the AlCl3 method, and antioxidant activity by two methods, namely FRAP and DPPH assay. The results showed that the highest levels of total phenolic, total flavonoid, and antioxidant activity of the DPPH method were obtained in Langkat accession. The highest antioxidant activity of FRAP assay was found in Malang accession. Total phenolic content had a statistically insignificant correlation with antioxidant activity. While the total flavonoid content correlated significantly and very strongly with the antioxidant activity of DPPH assay, but not in FRAP assay. The best gandarusa accession was Langkat.
Keyword: Aksesi, Antioksidan, Fenolik, Flavonoid, Gandarusa

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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