Judul: Total Fenolik, Flavonoid, dan Kapasitas Antioksidan Ekstrak Air Dari Tiga Aksesi Tanaman Gandarusa (Justicia gendarussa Burm.F).
Abstrak: Kadar fenolik dan flavonoid total serta kapasitas antioksidan pada tanaman obat seperti gandarusa (Justicia gendarussa Burm.F) dipengaruhi oleh banyak faktor, salah satunya perbedaan aksesi. Penelitian ini bertujuan menentukan nilai kadar fenolik dan flavonoid total serta kapasitas antioksidan dari tiga aksesi gandarusa yaitu aksesi Langkat, Malang dan Bekasi menggunakan air sebagai pelarut pengekstraksi. Penentuan kadar fenolik dilakukan dengan metode Follin- Ciocalteu, kadar flavonoid total ditentukan dengan metode AlCl3, dan kapasitas antioksidan dilakukan dengan metode FRAP (Ferric Reducing Antioxidant Power) dan DPPH (2,2’-difenil-1-pikrilhidrazil). Kadar fenolik total tertinggi sebesar 12,31 mg GAE g-1 bobot kering dan flavonoid total tertinggi sebesar 9,75 mg QE g-1 bobot kering serta kapasitas antioksidan (DPPH) tertinggi sebesar 8,04 μmol/g TEAC bobot kering ditemukan pada gandarusa aksesi Langkat. Sementara kapasitas antioksidan tertinggi dengan metode FRAP ditemukan pada gandarusa aksesi Bekasi sebesar 19,95 μmol TE g-1 bobot kering. Kadar fenolik dan flavonoid total memiliki korelasi signifikan dan sangat kuat terhadap kapasitas antioksidan secara statistika pada metode DPPH. Sementara kadar fenolik dan flavonoid total memiliki korelasi yang tidak signifikan terhadap kapasitas antioksidan pada metode FRAP. Simpulan hasil penelitian ini ditemukan bahwa aksesi gandarusa terbaik yaitu aksesi Langkat karena memiliki kadar nilai fenolik dan flavonoid total tertinggi serta nilai kapasitas antioksidan tertinggi menggunakan metode DPPH. Kata kunci: Aksesi, antioksidan, fenolik, flavonoid, gandarusa., Total phenolic and flavonoid levels as well as antioxidant capacity in medical plants such as gandarusa (Justicia gendarussa Burm. F) are influenced by many factors, one of which is accession differences. This study’s purpose is to determine the total phenolic and flavonoid levels and antioxidant capacity of three gandarusa accessions, namely the Langkat, Malang, and Bekasi using water as an extracting solvent. The phenolic content was determined by the Follin-Ciocalteu method, the total flavonoid content was determined by the AlCl3 method, and the antioxidant capacity was determined by the FRAP (Ferric Reducing Antioxidant Power) and DPPH (2,2’-diphenyl-1-pikrilhidrazyl) methods. Total phenolic content of 12.31 mg GAE g-1 dry weight and total flavonoids of 9.75 mg QE g-1 dry weight and the highest antioxidant capacity (DPPH) of 8.04 μmol TEAC g-1 dry weight were found in gandarusa accession Langkat. While the highest antioxidant capacity using the FRAP method was found in the gandarusa of the Bekasi highest antioxidant capacity using the FRAP method was found in the gandarusa of the Bekasi accession of 19.95 μmol TEAC g-1 dry weight. The levels of total phenolic and total flavonoids have a statistically significant and very strong correlation to antioxidant capacity in the DPPH method. Meanwhile, total phenolic and flavonoids level had no significant correlation to antioxidant capacity in the FRAP method. In conclusion, the result of this study found that the best gandarusa accession was the Langkat accession because it had the highest levels of total phenolic and flavonoid values and the highest antioxidant capacity values using the DPPH method. Keywords: Accession, antioxidant, flavonoid, gendarussa, phenolic.
Keyword: Accession, Antioxidant, Flavonoid, 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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