Judul: Inhibisi Radikal Dpph Oleh Fraksi Flavonoid Enam Tanaman Obat Dan Fraksi Aktif Terpilih
Abstrak: Masing-masing tanaman pulai (Alstonia scholaris), jabon merah (Anthocephalus macrophyllus), jati belanda (Guazuma ulmifolia), mindi (Melia azedarach), surian (Toona sinensis), dan salam (Syzgizium polyanthum) mengandung flavonoid sebagai antioksidan. Namun demikian, pemeringkatan aktivitas antioksidan fraksi flavonoid enam tanaman tersebut berdasarkan kekuatannya serta fraksi teraktif dari tanaman terpilih belum diketahui. Tujuan penelitian ini membandingkan aktivitas antioksidan fraksi flavonoid dari keenam tanaman tersebut dan memperoleh fraksi teraktif sebagai antioksidan dari ekstrak terpilih. Evaluasi aktivitas antioksidan melalui penangkapan radikal bebas DPPH menghasilkan salam sebagai tanaman terpilih dengan aktivitas antioksidan terkuat (IC50 8.57 μg/mL). Fraksinasi dengan kromatografi kolom menggunakan eluen kloroform, aseton, dan metanol dari fraksi flavonoid salam menghasilkan 11 fraksi aktif gabungan. Gabungan fraksi 8 merupakan fraksi teraktif sebagai antioksidan dengan nilai IC50 sebesar 10.35 μg/mL. Uji KLT bioautografi dengan DPPH dari fraksi teraktif menghasilkan pita kuning khas dengan nilai Rf 0.88. Nilai ini berbeda dengan nilai Rf standar rutin (0.25) dan kuersetin (0.93). Hal tersebut mengindikasikan bahwa senyawa yang berperan sebagai antioksidan bukan golongan flavonoid rutin dan kuersetin.
Keyword: antioksidan, flavonoid, kromatografi, Syzgizium polyanthum

Judul: Aktivitas Antioksidan dan Sitotoksisitas Metabolit Sekunder Daun Salam (Syzygium polyanthum Wight.) dan Daun Jati Belanda (Guazuma ulmifolia Lamk.)
Abstrak: Secondary metabolites from salam (Syzygium polyanthum Wight.) and jati belanda (Guazuma ulmifolia Lamk.) leaves can potentially be optimized for the utilization of these leaves as antioxidants. This research aimed to compare antioxidant activity and cytotoxicity of crude extracts of flavonoid, tanin, and hydroquinone of both type of leaves. Total phenolic and flavonoid compound was measured trough colorimetry, then the antioxidant activity was measured using 1.1-diphenil-2-picrylhydrazyl (DPPH) method and cytotoxicity test use brine shrimp lethality test (BSLT). Total phenolic value of salam leaves (614.70 mg GAE/100 g dried leaves) was higher when compared to jati belanda leaves (566.824 mg GAE/100 g dried leaves). Similarly, total flavonoids of salam leaves (434.234 mg QE/100 g dried leaves) was higher when compared to jati belanda leaves (246.214 mg QE/100 g dried leaves). This value is supported by IC50 values with DPPH method and LC50 values with cytotoxicity test showed the lowest IC50 and LC50 is flavonoid extract of salam leaves (IC50 = 10.833 μg/mL and LC50 = 328.427 μg/mL). Flavonoid of Salam leaves is the secondary metabolites with the best antioxidant activity and bioactivity effect.
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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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