Judul: Total Phenolic and Flavonoid Content and Antioxidant Capacity of Gendarussa Leaves (Justicia gendarussa Burm. f.) at Different Harvesting Ages
Abstrak: Pemilihan usia panen memengaruhi kadar senyawa fenolik, flavonoid, serta kapasitas antioksidan tanaman gandarusa (Justicia gendarussa Burm. f.). Penelitian ini bertujuan mengukur dan membandingkan fenolik total, flavonoid total, dan kapasitas antioksidan bagian daun tanaman gandarusa dengan berbagai usia panen. Daun gandarusa dengan usia 3, 4, 5, dan 6 bulan diekstrak menggunakan metode sonikasi dan maserasi. Kandungan fenolik total dan flavonoid total masing-masing diukur dengan metode Folin-Ciocalteu dan metode AlCl3. Aktivitas antioksidan diukur dengan metode 2,2-Diphenyl-1-picrylhydrazyl (DPPH) dan Ferric Reducing Antioxidant Power (FRAP). Hasil penelitian menunjukkan bahwa kadar fenolik total, flavonoid total, serta kapasitas antioksidan dengan metode DPPH dan FRAP tertinggi diperoleh masing-masing pada usia empat bulan (2,252 mg GAE/g DW), enam bulan (4,413 mg QE/g DW), tiga bulan (10,688 µmol TE/g DW), dan enam bulan (16,239 µmol TE/g DW). Penelitian ini menyimpulkan bahwa daun berusia enam bulan memiliki potensi terbaik karena memiliki kandungan senyawa flavonoid dan kapasitas antioksidan metode FRAP tertinggi., The selection of harvesting age affects the levels of phenolic compounds, flavonoids, and the antioxidant capacity of the gendarussa plant (Justicia gendarussa Burm. f.). This study aimed to measure and compare the total phenolic, total flavonoid, and antioxidant capacity of the leaves of the gandarusa plant at various harvesting ages. Gendarussa leaves at the ages of 3, 4, 5, and 6 months were extracted using sonication and maceration methods. Total phenolic content and flavonoids were measured using the Folin-Ciocalteu and AlCl3 methods, respectively. Antioxidant activity was measured using the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP) methods. The results showed that the highest levels of total phenolic, total flavonoids, and antioxidant capacity using the DPPH and FRAP methods were obtained at four months (2,252 mg GAE/g DW), six months (4,413 mg QE/g DW), three months (10,688 µmol TE/g DW), and six months (16,239 µmol TE/g DW), respectively. This study concludes that six-month-old leaves had the best potential because they had the highest content of flavonoid compounds and antioxidant capacity by the FRAP method.
Keyword: Antioksidan, Fenolik, Flavonoid, Gandarusa

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: 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.
Keyword: