Judul: Aktivitas Antioksidan dan Inhibisi Enzim α Glukosidase serta Toksisitas Ekstrak Air-Etanol dan Heksan Anggrek Merpati (Dendrobium cruminatum SW)
Abstrak: Dendrobium cruminatum are anggrek that grow in almost all regions of Indonesia. Dendrobium cruminatum leaves contain flavonoid compounds that are useful as an antioxidant and antidiabetic. This study aims to determine the ability of the anggrek merpati extract as an antioxidant and it’s potential to inhibition activity of α-glucosidase enzyme and also as a compound that toxic to the larvae of shrimp Artemia salina Leach with different solvents. The antioxidant activity was measured by using DPPH method and antidiabetic measured by the formation of p-nitrifenol-α-D-glukopiranosida (p-NPG) were measured with a spectrophotometer at a wavelength of 410 nm. The results of antioxidant activity and cytotoxicity testing showed that the best solvent used for the extraction of anggrek merpati leaf is water solvent with IC50 value of 153.565 μg / mL and the level of cytotoxicity was 889.641 mg / mL. whereas the activity of the inhibition of α-glucosidase enzyme is owned by the highest percentage of etanol by 64% at a concentration of 1000 μg / mL or IC50 value of 435 μg / mL.
Keyword: Bogor Agricultural University (IPB), antidiabetic and cytotoxicity., antioxidant, Dendrobium cruminatum

Judul: Aktivitas Antihiperglikemik dan Antioksidan Buah Bakau Merah (Rhizophora stylosa Griff.)
Abstrak: Red mangrove (R. stylosa) is one of rhizoporaceae which has been widely used as antidiabetic drugs. One of the way how to prevent and treat diabetic is by inhibiting activity of the enzyme α-glucosidase. The purpose of this research was to determine the antihyperglycemic activity of crude extract of the red mangrove (R. stylosa) fruit. The research was performed in several steps there were characterization of mangrove fruit, extraction (maceration), proximate test (AOAC 2005), toxicity test (BSLT), antihyperglycemic test (α-glucosidase inhibition), antioxidant test (DPPH), and phytochemical test (Harborne 1987). The result showed that the methanol extract had the highest yield compared to other extracts equal to 3.45%. The methanol extract possessed the most toxic with LC50 values of 116.96 ppm. Ethyl acetate extract had the highest value of α-glucosidase inhibition (IC50) in the amount of 285.56 ppm, followed by methanol extract of 474.97 ppm, and n-hexane extract of >15000 ppm. The antioxidant test result of ethyl acetate extract showed IC50 value 79.71 ppm. Phytochemical test of ethyl acetate extract showed positive results on phenol hydroquinone, flavonoid, steroid and triterpenoid
Keyword: Bogor Agricultural University (IPB), α-glucosidase, toxicity, red mangrove, phytochemical, Antioxidant

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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