Judul: Optimization of Extraction of Antimicrobial Peptide from Gandarusa Leaves Using the Box-Behnken Design
Abstrak: Antimicrobial Peptide (AMP) memiliki aktivitas spektrum luas dan dapat membunuh bakteri yang resistan terhadap berbagai obat. Daun gandarusa (Justicia gendarussa Burm. F.) memiliki aktivitas antibakteri namun kajian terkait antimicrobial peptide pada tanaman tersebut belum dilakukan. Penelitian ini bertujuan menentukan kondisi optimum ekstraksi serta mengidentifikasi AMP daun gandarusa yang berpotensi memiliki aktivitas antibakteri. Rancangan optimasi ekstraksi dibuat menggunakan Box-Behnken Design. Kadar total protein diukur dengan metode Bradford, identifikasi AMP dilakukan dengan metode SDS-PAGE, dan pengujian aktivitas antibakteri dilakukan dengan metode difusi sumuran. Hasil penelitian menunjukkan kondisi optimum ekstraksi diperoleh dari kombinasi konsentrasi pelarut 14,997%, waktu ekstraksi 2,998 jam, dan rasio antara sampel dengan pelarut yaitu 1:3. Identifikasi dengan SDS-PAGE menunjukkan AMP terduga dari daun gandarusa memiliki berat molekul sebesar 11 kDa, pengujian aktivitas antibakteri ekstrak kasar terhadap Escherichia coli dan Staphylococcus aureus tidak menunjukkan adanya daya hambat., Antimicrobial Peptide (AMP) has broad-spectrum activity and can kill multidrug-resistant bacteria. Gandarusa leaves (Justicia gendarussa Burm. F.) have antibacterial activity, but studies regarding antimicrobial peptides in this plant have not been carried out. This study aimed to determine the optimum conditions of extraction and identify AMPs of gandarusa leaves that have potential antibacterial activity. Extraction optimization design was made using Box-Behnken Design. Total protein levels were measured by the Bradford method, AMP identification was carried out by the SDS-PAGE method, and antibacterial activity testing was carried out by the well diffusion method. The results showed that the optimum extraction conditions were obtained from a combination of 14,997% solvent concentration, 2,998 hours extraction time, and the ratio between sample and solvent of 1:3. Identification with SDS-PAGE showed that AMP from gandarusa leaves has a molecular weight of 11 kDa, testing the antibacterial activity of crude extracts against Escherichia coli and Staphylococcus aureus showed no inhibition.
Keyword: antimicrobial peptide, Box-Behnken design, Gandarusa leaves, optimization

Judul: Optimization of Extraction for Total Phenolics and Highest  Antioxidant Capacity in Gandarusa Using Two-Level Half Factorial Design
Abstrak: Gandarusa (Justicia gendarussa Burm. f.) telah digunakan sebagai obat tradisional dan dilaporkan memiliki senyawa fitokimia dan aktivitas antioksidan yang tinggi. Penelitian ini bertujuan untuk mengukur pengaruh perbedaan kondisi ekstraksi berdasarkan rasio cairan terhadap padatan, suhu, konsentrasi pelarut, waktu, dan pH tanaman gandarusa dengan two level half factorial design terhadap produksi metabolit sekunder dan kapasitas antioksidannya. Sampel diekstraksi sesuai dengan desain two level half factorial. Kandungan fenolik, kapasitas antioksidan DPPH dan FRAP tertinggi didapat oleh run-13 berturut-turut sebesar 28,15 mg GAE/g, 54,19 μmol TE/g, dan 218,73 μmol TE/g. Desain two level factorial digunakan untuk menentukan faktor yang signifikan terhadap ekstraksi kadar fenolik total, serta kapasitas antioksidan DPPH dan FRAP. Faktor suhu berperan signifikan (< 0,05) terhadap kadar fenolik total. Sedangkan pada kapasitas antioksidan DPPH didapatkan bahwa faktor cairan terhadap padatan dan pH berperan signifikan (< 0,05). Pada FRAP didapatkan bahwa faktor cairan terhadap padatan menjadi faktor yang berperan signifikan (< 0,05). Kata kunci: antioksidan, factorial, gandarusa, cairan terhadap padatan, suhu, Gandarusa (Justicia gendarussa Burm. f.) is often used as a traditional medicine and is reported to contain high levels of phytochemical compounds and antioxidant activity. This study aimed to measure the influence of different extraction conditions based on liquid to solid ratio, temperature, solvent concentration, time, and pH of gandarusa plant on the production of secondary metabolites and antioxidant capacity using a two-level half factorial design. Samples were extracted according to the two-level half factorial design. The highest phenolic content, DPPH and FRAP antioxidant capacity were obtained from run 13, with values of 22.75 mg GAE/g, 43.36 μmol TE/g, and 166.72 μmol TE/g, respectively. A two-level factorial design was used to determine the significant factors affecting the extraction of total phenolic content, DPPH antioxidant capacity, and FRAP antioxidant capacity. Temperature was found to have a significant effect (<0.05) on the total phenolic content. Meanwhile, for DPPH antioxidant capacity, the liquid to solid ratio and pH was found to be the significant factor (<0.05). In FRAP, it was found that the liquid to solid factor was a significant factor (<0.05). Keyword: antioxidant, factorial, gandarusa, liquid to solid, temperature
Keyword: antioxidant, factorial, gandarusa, liquid to solid, temperature

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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