Judul: Penambatan Molekuler Senyawa Kurkuminoid, Xanthorizol, β-Elemenon, Zedoaron terhadap Aktivitas Inhibisi Enzim Dipeptidil Peptidase IV.
Abstrak: Kasus diabetes mellitus (DM) terus meningkat setiap tahunnya, terutama diabetes mellitus tipe II yang disebabkan oleh adanya resistensi insulin oleh sel tubuh. Salah satu pengobatan penyakit DM tipe II yang sedang berkembang saat ini adalah inhibitor enzim dipeptidil peptidase IV (DPP IV). Tumbuhan Curcuma yang banyak dimanfaatkan sebagai obat herbal, mengandung senyawa kurkuminoid yang memiliki aktivitas antidiabetes sehingga berpotensi sebagai inhibitor DPP IV. Penelitian ini bertujuan memprediksi potensi inhibisi kurkuminoid dan beberapa senyawa aktif tumbuhan Curcuma lainnya terhadap aktivitas enzim DPP IV secara in silico melalui simulasi penambatan molekuler. Gosogliptin digunakan sebagai ligan kontrol dan sitagliptin sebagai pembanding. Ligan-ligan uji dengan potensi inhibisi tertinggi hingga terendah antara lain bismemetoksikurkumin, demetoksikurkumin, kurkumin, zedoaron, β-elemenon, dan xanthorizol. Senyawa bisdemetoksikurkumin merupakan ligan uji terbaik sebagai inhibitor DPP IV dengan binding site similarity sebesar 70% dan energi afinitas -6.5 kkal/mol. Kurkuminoid, xanthorizol, β-elemenon, dan zedoaron dapat menjadi alternatif pengobatan bagi pasien DM tipe II.
Keyword: Curcuma, diabetes, DPP IV, penambatan molekuler

Judul: In Silico Analysis of Activity Caffeic Acid Derivate in Echinacea (Echinacea purpurea (L). Moench.) against Dipeptidyl Peptidase-IV
Abstrak: Kasus diabetes mellitus (DM) telah menjadi masalah kesehatan global, terutama DM tipe II. Salah satu pengobatan DM tipe II yang menarik diteliti ialah inhibitor dipeptidil peptidase-IV (DPP-IV) karena perannya meningkatkan sekresi insulin dan proliferasi sel β-pankreas. Tanaman ekinase (Echinacea purpurea (L). Moench.) telah banyak dimanfaatkan sebagai obat herbal, mengandung asam kafeat dan derivatnya yang memiliki aktivitas antidiabetes. Penelitian ini bertujuan menganalisis interaksi molekuler serta hubungan struktur terhadap potensi inhibisi derivat asam kafeat ekinase terhadap aktivitas DPP-IV melalui kajian in silico menggunakan YASARA Structure. Gosogliptin (Pf2) digunakan sebagai ligan native dan sitagliptin sebagai pembanding. Ligan-ligan uji dengan potensi inhibisi tertinggi hingga terendah antara lain echinacoside, asam sikorat, cynarine, acteoside, asam klorogenat, asam kaftarat, asam isoklorogenat, dan asam kafeat. Echinacoside yang merupakan senyawa penciri ekinase menjadi ligan uji terbaik sebagai inhibitor DPP-IV dengan energi bebas ikatan -9.731 kkal/mol, namun kurang baik sebagai obat oral. Asam sikorat merupakan ligan terbaik yang dapat menjadi alternatif obat oral dalam pengobatan DM tipe II., Diabetes mellitus case has become a global health problem, especially the type II. One of the most interesting treatments for type II DM is dipeptidyl peptidase-IV (DPP-IV) inhibitors which promote insulin secretion and proliferation pancreatic β cells. Ekinase (Echinacea purpurea (L). Moench.), which have been utilized as a herbal medication, contain caffeic acid and derivatives compound that has antidiabetic activity. This research is aimed to analyze molecular interactions and structural relationship to the inhibition potency of caffeic acid and derivatives against DPP-IV activity using docking simulation with YASARA Structure. Gosogliptin (Pf2) was used as native ligand and sitagliptin as comparator. Test ligands with the highest to lowest inhibition potency are echinacoside, chicoric acid, cynarine, acteoside, chlorogenic acid, caftaric acid, isochlorogenic acid, and caffeic acid. Echinacoside is the characteristic compound from echinacea, becomes the most potent DPP-IV inhibitor which shows -9.731 kcal/mol on affinity energy, but not recommended as oral drug. Chicoric acid is the best ligand that can be an alternative treatment as oral drug for type II of DM.
Keyword: Diabetes, Docking, DPP-IV, Echinacea

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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