Judul: Aktivitas Ekstrak Daun Sirsak Sebagai Inhibitor Enzim Alfa Glukosidase (In Vitro) Dari Sembilan Lokasi Di Jawa Barat.
Abstrak: Ekstrak daun sirsak (Annona muricata L.) dapat dimanfaatkan sebagai agen antidiabetes dengan cara menghambat kerja enzim α-glukosidase secara in vitro melalui senyawa bioaktif yang terkandung di dalam ekstrak. Pada penelitian ini, daun sirsak diambil dari lokasi Desa Leuwigoong (Garut I), Desa Cangkuang (Garut II), Desa Kadungora (Garut III), Desa Sukasirna (Cianjur I), Desa Sukasarana (Cianjur II), Desa Ciherang (Cianjur III), Desa Karangpapak Jenis Ratu (Sukabumi I), Desa Karangpapak Jenis Asam (Sukabumi II), dan Desa Sukasari (Sukabumi II). Proses maserasi dilakukan dengan menggunakan dua jenis pelarut, etanol 70% dan air. Ekstraksi menggunakan metode microwave agar lebih memudahkan pengeluaran senyawa bioaktif. Ekstrak etanol dan air diukur kadar air, jumlah rendemen, uji fitokimia, uji GC-MS, penentuan kadar total fenol, dan uji inhibisi. Hasil uji fitokimia menunjukkan hasil yang positif, kecuali untuk pengujian keberadaan senyawa golongan steroid. Hasil screening senyawa GC-MS menunjukkan adanya senyawa golongan fenol (benzamida, benzokuinon, vinil fenol), senyawa golongan alkaloid (piperin dan piperidin), dan senyawa antioksidan (tokoferol). Hasil penentuan total komponen fenolik menunjukkan sampel lokasi Sukabumi I menjadi sampel dengan total fenolik tertinggi baik ekstrak etanol (49.40±1.05) maupun ekstrak air (36.98±0.17). Persen inhibisi terbesar pada ekstrak etanol konsentrasi 1% berasal dari lokasi Sukabumi I sebesar 96.83±1.42, konsentrasi 1.5 % dari lokasi Sukabumi III sebesar 98.94±0.54, dan konsentrasi 2% berasal dari Sukabumi II sebesar 99.35±0.31, sedangkan ekstrak air pada konsentrasi 1%; 1.5%; dan 2% menunjukkan Cianjur sebagai lokasi dengan persen inhbisi tertinggi sebesar 71.15±2.61; 79.37±2.18; dan 93.46±3.60. Jumlah yang banyak dari setiap ekstrak mampu bekerja dalam menghambat enzim α-glukosidase secara in vitro.
Keyword: α-glukosidase, Annona muricata L, antidiabetes

Judul: Aktivitas antidiabetes ekstrak air dan etanol daun sirsak secara in vitro melalui inhibisi enzim α-glukosidase
Abstrak: Soursop leaf is a part of the soursop plant used in traditional medicine and proven for antidiabetic agent through decrease in blood glucose level. However, the mechanism of decrease in blood glucose level has not been determined. The research was done to determine the activity of aqueous and ethanol extract of soursop leaf at 1, 1.50, 2% as α-glucosidase inhibitor, compared their activities with acarbose 1% as positive control and determine the mechanism of inhibition. Soursop leaf were extracted with ethanol 70% using maceration method and boiling water method. Aqueous and ethanol extract of soursop leaf were used for phytochemical assay and used for α-glucosidase inhibition method. The α- glucosidase activity was determined by measuring the p-nitrophenol release from the reaction of the enzyme and substrate p-nitrophenil- α-D-glucopiranoside (p- NPG) at 400 nm. The phytochemical analysis indicates that aqueous extract and ethanol extract contained alkaloid, flavonoid, saponin, tannin, and steroid. Both of them can inhibit α-glucosidase activity, but the mechanism of inhibition of the extract has not been able to determined. Aqueous extract can inhibit α-glucosidase activity up to 41.91%, and ethanol extract can inhibit α-glucosidase activity up to 89.33%. Acarbose as positive control can inhibit 93.84% of α-glucosidase activity.
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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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