Judul: Activities of suren (Toona sinensis Merr.) bark extracts as antioxidant and antidiabetic with in vitro analysis.
Abstrak: Suren (Toona sinensis Merr.) is a herbal plant that its leaves has been reported have a antioxidant and antidiabetic activity. The bark of suren thought to have antioxidant and antidiabetic activity as it leaves. This study was conducted to investigate antioxidants and antidiabetic activity of ethanol 70% and water extracts of suren bark using in vitro method. The antioxidant activity was observed using the parameters of biochemical tests, through measurement of the inhibitory activity to DPPH as free radical with concentration of samples 50, 30, 10, and 5 ppm. The potential antidiabetic activity was measured through inhibition of -glucosidase enzymes work at a sample concentration of 12.5, 6.3, 3.1, and 1.6 ppm. The moisture content of suren bark samples in the test is 9.04%. Suren bark extracted with a solvent ethanol 70% and water has a yield of 4.8% and 2.6%. Phytochemical test of ethanol 70% extract showed the present of alkaloids, saponins, tannins, flavonoids, and hydroquinone. While the water extract indicate a content of saponin compounds, flavonoids, and hydroquinone. The results of the analysis of antioxidant activity indicated by IC50 value which is 11.86 ppm for ethanol 70% extracts and 17.78 ppm for water extract. While the IC50 value of vitamin C used as a comparison is 3.31 ppm. Inhibition of - glucosidase enzyme are also shown in the IC50 value which is 0.66 ppm for ethanol 70% extract and 3.32 ppm for water extracts, whereas acarbose as a comparison have IC50 value of 0.08 ppm. These results showed that suren bark have an antioxidant and antidiabetic activity. Key words: antioxidant, antidiabetic, suren (Toona sinensis Merr.) DPPH, a- glucosidase
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Judul: Inhibition Activity of a-Glucosidase and Total Alkaloid Content of Crude Ethanol Extract from Surian Leaves (Toona sinensis) Leaves at Various Tree Ages
Abstrak: Daun surian (Toona sinensis) mengandung banyak senyawa fitokimia dengan aktivitas seperti antioksidan, antidiabetes, antihiperlipidemia, dan antikanker. Diabetes melitus merupakan gangguan metabolik kronis yang ditandai oleh tingginya kadar gula darah akibat masalah dalam produksi atau fungsi insulin. Prevalensi diabetes melitus pada tahun 2013 di seluruh dunia mencapai 8,4%. Alkaloid merupakan jenis senyawa organik yang mengandung nitrogen, seperti kafein. Kafein, yang ditemukan dalam berbagai jenis daun, memiliki sifat stimulan yang dikenal luas. Penelitian ini menguji aktivitas penghambatan a-Glukosidase dan kadar total alkaloid pada ekstrak etanol daun surian pada umur 11, 27, dan 34 tahun menggunakan pelarut etanol 30%, 70%, dan 96%. Hasilnya menunjukkan pengaruh pelarut dan umur pohon terhadap aktivitas penghambatan enzim aglukosidase dan kadar alkaloid. Aktivitas terbesar terjadi pada ekstrak etanol 96% dari daun surian umur 34 tahun, dengan nilai IC50 sebesar 7,3 µg/mL. Kadar alkaloid tertinggi juga ditemukan pada ekstrak etanol 96% dari daun surian umur pohon 34 tahun, sebesar 3,82%., Surian leaves (Toona sinensis) contained numerous phytochemical compounds with activities such as antioxidant, antidiabetic, antihyperlipidemic, and anticancer. Diabetes mellitus was a chronic metabolic disorder characterized by high blood sugar levels due to issues with insulin production or function. The global prevalence of diabetes mellitus in 2013 reached 8,4%. Alkaloids were a type of organic compound containing nitrogen, such as caffeine. Caffeine, found in various types of leaves, was widely known for its stimulant properties. This study examined the a-glucosidase inhibitory activity and total alkaloid content in ethanolic extracts of surian leaves aged 11, 27, and 34 years using 30%, 70%, and 96% ethanol solvents. The results indicated the influence of solvent and tree age on a-glucosidase enzyme inhibition activity and alkaloid content. The greatest activity occurred in the 96% ethanol extract from 34-year-old surian leaves, with an IC50 value of 7,3 µg/mL. The highest alkaloid content was also found in the 96% ethanol extract from 34-year-old surian leaves, amounting to 3,82%.
Keyword: antidiabetic, Toona sinensis, a-Glucosidase, alkaloid, caffeine

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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