Judul: Kajian Aktivitas Antibakteri Daun Gatel (Laportea decumana (Roxb.) Wedd.) dan Daun Benalu Cengkeh
Abstrak: Many researches showed that several plants have a good antibacterial activity. The leaves of gatel and clove mistletoe are empirically used to cure several diseases. The aims of this research were: (1) to study the potential of antibacterial activity of gatel and clove mistletoe hexane, ethyl acetate and methanol extracts against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa by the well diffusion method; (2) to calculate the minimum inhibitory concentration (MIC) value of the potential extracts; and (3) to study the effect of various pH to antibacterial activity of the extracts. The results showed ethyl acetate and methanol extracts of the studied plants have low antibacterial activity against B. cereus and E. coli. Based on the MIC values, the ethyl acetate extract of gatel leaves showed over 99% percent inhibition against E. coli at a concentration of 3.5%, 4.0%, 4.5% and 5.0%. The same result was obtained by modifying the pH (4, 5 and 6) at the extracts concentration of 5% and 10%. The methanol extract of gatel leaves showed below 60% inhibition of B. cereus at a concentration of extract 4.0%, 4.5%, 5.0%, 5.5% and 6.0%, and more than 90% inhibition at the pH. The ethyl acetate extract of clove mistletoe showed more than 98% inhibition againts E. coli at a concentration of 3.5%, 4.0%, 4.5% and 5.0% and at pH 4, 5 and 6. Percent of inhibition less than 50% occured in the methanol extract of clove mistletoe at 4.0%, 4.5%, 5.0%, 5.5% and 6.0% concentration against B. cereus. For the methanol extract of clove mistletoe, the effect of pH variation (4, 5, 6 and 7) resulted in 92%-97% inhibition. The result may increase the utilization of research plant not only for health purposes but also as a natural food preservative and open new possibilities for the development of natural functional foods.
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Judul: Antibacterial Testing and Metabolomic Analysis of Ethanol Extract from Basil Leaves from Three Regions
Abstrak: Kemangi merupakan tumbuhan obat yang banyak dijumpai di Indonesia dan dilaporkan memiliki aktivitas antibakteri. Penelitian mengenai antibakteri perlu terus dilakukan seiring meningkatnya kasus resistensi antibiotik. Uji antibakteri dan analisis metabolomik pada ekstrak etanol daun kemangi yang dibudidayakan di tiga daerah asal (Banyuwangi, Cibungbulang, dan Dramaga) belum pernah dilakukan sebelumnya. Penelitian ini bertujuan menguji aktivitas antibakteri, mengidentifikasi senyawa, serta mendeskripsikan aktivitas biologis dari senyawa yang terkandung dalam ekstrak etanol daun kemangi asal Banyuwangi, Cibungbulang, dan Dramaga. Ektraksi daun kemangi dilakukan menggunakan teknik maserasi dengan pelarut etanol 96%. Ekstrak diencerkan menggunakan DMSO 10% menghasilkan konsentrasi 10%, 20%, 40%, dan 60%. Setiap konsentrasi diuji aktivitas antibakteri menggunakan metode difusi cakram. Pengujian antibakteri dilakukan terhadap bakteri Bacillus subtilis ATCC 19659, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 15442. Analisis metabolomik dilakukan menggunakan GC-MS. Ekstrak etanol kemangi konsentrasi 40% dan 60% asal Banyuwangi, Cibungbulang, dan Dramaga dapat menghambat pertumbuhan Bacillus subtilis, tetapi tidak menghambat tiga jenis bakteri lainnya. Hasil analisis metabolomik menunjukkan bahwa ketiga sampel kemangi memiliki 12 senyawa yang sama. Senyawa mayor yang terdeteksi adalah salvigenin (Banyuwangi), salvigenin dan phytol (Cibungbulang), serta salvigenin dan linalool (Dramaga). Ketiga jenis senyawa mayor tersebut dilaporkan memiliki aktivitas antibakteri., Basil is a medicinal plant in Indonesia and reported to have antibacterial activity. Research on antibacterials needs to be continuously conducted due to the increasing cases of antibiotic resistance. Antibacterial testing and metabolomic analysis on ethanol extracts of basil leaves from Banyuwangi, Cibungbulang, and Dramaga have not been previously conducted. Therefore, this study aims to test the antibacterial activity, identify compounds, and describe the biological activities of the compounds. The maceration of basil leaves was performed with 96% ethanol as the solvent. The extracts were diluted using 10% DMSO to obtain concentrations of 10%, 20%, 40%, and 60%. Each concentration was tested for antibacterial activity using the disc diffusion method against Bacillus subtilis ATCC 19659, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 8739, and Pseudomonas aeruginosa ATCC 15442. Metabolomic analysis was carried out using GC-MS. The 40% and 60% ethanol extracts of basil from three regions were able to inhibit te growth of Bacillus subtilis, but did not inhibit the other three bacterial strains. All three samples of basil have 12 identical compounds. The major coupounds detected are salvigenin (Banyuwangi), salvigenin and phytol (Cibungbulang), salvigenin and linalool (Dramaga). All these major compounds have been reported to have antibacterial activity.
Keyword: maceration technique, metabolomics, disc diffusion method

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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