Judul: Potensi Antioksidan, Inhibitor Tirosinase, dan Nilai Toksisitas dari Beberapa Spesies Tanaman Mangrove di Indonesia
Abstrak: Indonesia is a country rich in biodiversity. Mangrove is a plant that quite a lot in Indonesia. This research was conducted to determine potency of antioxidant, tyrosine inhibitors, and toxicity from some types of mangrove plants. The result showed that the yield of R. stylosa bark extract was 18.07% and it was the highest yield extract. S. caseolaris fruit extract had the lowest LC50 of toxicity (126.73 μg/mL). S. caseolaris bark extract had antioxidant best value with IC50 of 3.03 μg/mL. This extract also had the best potency of tyrosinase inhibitors with IC50 value of 117.67 mg/mL for monophenols and 364.99 mg/mL for diphenols. Active compounds detected in S. caseolaris extract were tannins, saponin, flavonoid, and phenol hydroquinone. S. caseolaris bark extract was the best extract due to the best ability of antioxidant activity and tyrosinase inhibitory activity.
Keyword: Bogor Agricultural University (IPB), toxicity, mangrove, inhibitors tyrosinase, best extract, antioxidant

Judul: Eksplorasi Potensi Bahan Aktif Berkhasiat Antioksidan Pada Daun dan Buah Mangrove Jenis Sonneratia alba (JE Smith, 1816)
Abstrak: Sonneratia alba has been used traditionally by coastal communities for drugs and foodstuffs. Antioxidants are compounds that was result from plant secondary metabolites and that has been helpful for humans to protect from free radical attack when it consumed. The purpose of this research is to obtain a total phenol values, IC50 concentrations and the relationship of both, from methanol extract of young leaves, old leaves and fruits of Sonneratia alba then to identify the phytochemical content. The experiments antioxidant activity using 1,1-diphenyl-2-pikrilhidrazil (DPPH). Total phenol values in the three extracts showed theres no significantly values. DPPH test showed that IC50 concentrations in the sample extracts are classified into three powerful antioxidants, the young leaf extract showed highest antioxidant activity of 37.43 ppm. Regression between total phenols with IC50 showed no significant. So, there are other compounds that affect the value of IC50. Based on phytochemical test, the chemical components of dried simplicia contained flavonoids, saponins, tannins, and steroids on the three samples.
Keyword: Bogor Agricultural University (IPB), Sonneratia alba, DPPH, leaves, fruits, antioxidants

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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