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: Potensi Ekstrak Rhizophora sp. sebagai Inhibitor Tirosinase
Abstrak: Rhizophora sp. is one of plant type that has benefit as medicinal plants, for example, as whitening agent. The purpose of this study is to discover the parts and species of Rhizophora sp. which have best tyrosinase inhibitory activity. Leaves, stems, and roots of R. mucronata and R. stylosa were extracted with methanol and were tested their activities in order to obtain the best tyrosinase inhibitory activity. Based on the results, extracts of leaves, stems, and roots of R. mucronata from Tritih, Cilacap; Gebang, Cirebon; Eretan Kulon, Indramayu; Ujung Negoro Beach, Batang; Sigundu Beach, Batang; and Kapuk Beach, Jakarta were not potencial as tyrosinase inhibitor. Tyrosinase inhibitor activity from roots of R. mucronata from Samboja, East Kalimantan was higher than from its leaves and stems, especially for monophenolase with IC50 15.34 μg/ml. In perponderonce with, tyrosinase inhibitor activity from stems of R. stylosa from Samboja, East Kalimantan was also higher compared with stems of R. mucronata with IC50 38.02 μg/ml.
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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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