Judul: Total Phenolic Content and Antioxidant Activity of Gandarusa Leaf (Justicia gendarussa Burm.f.) Extract with Difference of Concentraction of Solvent and Duration of Extraction
Abstrak: Konsentrasi pelarut yang digunakan dalam ekstraksi dan durasi ekstraksi akan memengaruhi kadar total fenolik dan aktivitas antioksidan daun gandarusa. Penelitian ini bertujuan untuk mengukur dan membandingkan pengaruh antara konsentrasi pelarut dan durasi ekstraksi daun gandarusa terhadap kadar total fenolik dan aktivitas antioksidan. Daun gandarusa diekstraksi dengan menggunakan pelarut metanol pada konsentrasi dan durasi yang berbeda. Kadar total fenolik diukur dengan menggunakan Uji Folin-Ciocalteu dan aktivitas antioksidan diukur dengan menggunakan uji DPPH dan CUPRAC. Kadar total fenolik tertinggi terdapat pada perlakuan konsentrasi metanol sebesar 30% dengan durasi 180 menit (0,1024 mg GAE/g bobot kering). Aktivitas antioksidan tertinggi pada uji DPPH (0,1853 μmol TE/g bobot kering) dan CUPRAC (5,2444 μmol TE/g bobot kering) terdapat pada perlakuan konsentrasi metanol 30% dengan durasi 180 menit., Concentration of solvent and duration of extraction will affect the total phenolic content and antioxidant activity of gandarusa leaf. This research was aimed to measure and compare the effect of concentration of solvent and duration of extraction on Total Phenolic Content (TPC) and antioxidant activity. Gandarusa leaf was extracted using the methanol solvent with different concentration and duration. Total phenolic content was measured with FolinCiocalteu and antioxidant activity was measured with DPPH and CUPRAC. The highest TPC is gandarusa leaf’s extract with 30% of methanol for 180 minutes (0,1024 mg GAE/mg dry weight). The highest antioxidant activity with DPPH (0,1853 µmol TE/gr dry weight) and CUPRAC (5,2444 µmol TE/gr dry weight) is gandarusa leaf’s extract with 30% of methanol for 180 minutes
Keyword: Antioxidant Activity, Concentration of Solvent, Duration of Extraction, Gandarusa Leaf, Phenolic

Judul: Kandungan Fenolik dan Aktivitas Antioksidan Ekstrak Daun Gandarusa Hasil Optimasi Pelarut dengan Metode Sonikasi
Abstrak: Gandarusa (Justicia gendarussa Burm. f.) merupakan tanaman obat yang memiliki senyawa antioksidan untuk menangkal radikal bebas karena adanya kandungan metabolit sekunder seperti senyawa fenolik. Kandungan fenolik yang terekstrak serta nilai aktivitas antioksidan dapat dipengaruhi oleh pemakaian pelarut ekstraksi. Penelitian ini bertujuan menentukan pelarut terbaik antara air, etanol, dan asam asetat serta kombinasi ketiganya untuk ekstraksi daun tanaman gandarusa menggunakan metode sonikasi terhadap kadar total fenolik serta aktivitas antioksidan (metode DPPH dan FRAP) secara in vitro. Hasil penelitian menunjukkan bahwa nilai verifikasi yang diperoleh terhadap kadar total fenolik dan aktivitas antioksidan tidak berbeda jauh dengan nilai prediksinya dari software Design-Expert metode simplex lattice design (SLD), yaitu sebesar 3,257 mg GAE/g bobot kering pada kadar total fenolik, 0,182 µmol TE/g bobot kering pada aktivitas antioksidan metode DPPH, dan 8,117 µmol TE/g bobot kering pada aktivitas antioksidan metode FRAP dengan nilai desirability sebesar 0,621. Hal ini dilihat dari nilai signifikansi (p-value) pada kadar total fenolik dan aktivitas antioksidan yang menunjukkan lebih besar dari 0,05., Gendarussa (Justicia gendarussa Burm. f.) is a medicinal plant that has antioxidant compounds to counteract free radicals due to the content of secondary metabolites such as phenolic compounds. The extracted phenolic content and antioxidant activity value can be affected by the use of extraction solvent. This study aimed to determine the best solvent between water, ethanol, and acetic acid and their combination for extracting the leaves of the gendarussa plant using the sonication method on total phenolic content and antioxidant activity (DPPH and FRAP methods) in vitro. The results showed that the verification value obtained for total phenolic content and antioxidant activity did not differ much from the predicted values from Design-Expert software simplex lattice design (SLD) method, which was 3.257 mg GAE/g dry weight on total phenolic content, 0.182 µmol TE/g dry weight on antioxidant activity of DPPH method, and 8.117 µmol TE/g dry weight on antioxidant activity of FRAP method with a desirability value of 0.621. This can be seen from the significance value (p-value) on total phenolic content and antioxidant activity which showed greater than 0.05.
Keyword: antioxidant activity, DPPH, FRAP, 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.
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