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 dan Kapasitas Antioksidan Tanaman Gandarusa (Justicia gendarussa Burm.f.) Terhadap Perlakuan Waktu Perebusan Daun yang Berbeda
Abstrak: Tanaman gandarusa (Justicia gendarussa Burm. f.) merupakan tumbuhan semak yang umumnya tumbuh liar dan dipelihara sebagai tanaman obat serta berpotensi sebagai antioksidan. Potensi ini dikarenakan adanya kandungan berbagai jenis metabolit sekunder pada tanaman tersebut, salah satunya fenolik. Penelitian ini bertujuan menganalisis pengaruh waktu perebusan daun gandarusa terhadap kadar total fenolik dan kapasitas antioksidan metode Ferric Reducing Antioxidant Power (FRAP) dan 1,1-diphenyl-2-picrylhydrazyl (DPPH). Sampel diekstraksi dengan metode gabungan sonikasi dan maserasi. Daun gandarusa dilakukan perlakuan pemanasan yaitu perebusan menggunakan waterbath. Kadar total fenolik diukur menggunakan metode Folin-Ciocalteu dan kapasitas antioksidan menggunakan metode FRAP dan DPPH. Hasil penelitian menunjukkan ekstrak daun gandarusa dari ketiga perlakuan memiliki kadar total fenolik tertinggi pada perlakuan 1 yaitu sampel yang tidak direbus dibandingkan dengan sampel yang direbus sebesar 4.346 (mg GAE/g BK). Begitu pula dengan hasil kapasitas antioksidan FRAP dan DPPH didapat sampel daun yang tidak rebus memiliki kapasitas antioksidan tertinggi dibandingkan dengan sampel yang rebus sebesar 31.033 (µmol TE/g BK) dan 383.851 (µmol TE/g BK)., Gandarusa plant (Justicia gendarussa Burm. f.) is a shrub that generally grows wild and is maintained as a medicinal plant and has potential as an antioxidant. This potential is due to the content of various types of secondary metabolites in these plants, one of which is phenolic. This study aims to analyze the effect of boiling time for willow leaves on total phenolic content and antioxidant capacity using the Ferric Reducing Antioxidant Power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) methods. Samples were extracted by a combined method of sonication and maceration. Gandarusa leaves are subjected to heating treatment, namely boiling using a water bath. Total phenolic content was measured using the Folin-Ciocalteu method and antioxidant capacity using the FRAP and DPPH methods. The results showed that the gandarusa leaf extract from the three treatments had the highest Total phenolic content in treatment 1, namely the unboiled sample compared to the boiled sample, which was 4,346 (mg GAE /g DW). Likewise, with the results of the FRAP and DPPH antioxidant capacity, it was found that unboiled leaf samples had the highest antioxidant capacity compared to boiled samples, namely 31,033 (µmol TE/gDW) and 383,851 (µmol TE/g DW).
Keyword: Antioxidants, phenolics, boiling, 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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