Judul: Pengaruh Waktu Pemasakan dan Konsentrasi Terhadap Aktivitas Antioksidan dan Kadar Fenolik Total Brokoli (Brassica oleracea L. var. italica)
Abstrak: There are many plants that can be used as alternative medicine. One of them is broccoli which is known as vegetable that contain antioxidant, such as phenolic compounds. Antioxidant is capable to inhibit free radicals in human tuJy. This research was aimed to measure the effect of cooking time and concentration of broccoli on antioxidants activity tested by DPPH (1,I-diphenyl-2-pycrilhydrazil) method and total phenolic content. Butylated hydroxytoluene (BHT) was used as positive control with various concentrations, 2, 4, 6, and 8 ppm. Some samples were cooked by conventional boiling treatment for 10, 20, and 30 minutes, and then were extracted with methanol. The extracts were separated by flash chromatography with toluene:ethyl acetate (11:9) as mobile phase. The number of fractions were determined with bioautography thin layer chromatography that were sprayed with DPPH 0.004% to get the active fraction. The methanol extracts and the active fractions were diluted to various concentrations, 10, 30, 50, and 70 ppm and then were determined for their antioxidant activity and the total phenolic content. The results showed that cooking time of broccoli from 10 to 30 minutes were significantly decreased antioxidant activity of extracts while increasing concentration of extract and active fraction from 10 to 70 ppm increase antioxidant activity of both of them. The ICso value of methanol extracts and active fraction were 226.94 and 221.78 ~g/mL, respectively. The ICso value of BHT was 6.46 ~g/mL. The total phenolic content active fraction for raw vegetable, 10, 20, and 30 minutes cooking time were 764.91, 495.96, 441.19, dan 304.66 mg/lOOg, respectively. Total phenolic content of broccoli were significantly decreased during the cooking.
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Judul: Isolasi Senyawa Lutein dari Ekstrak Bunga Brokoli sebagai Antioksidan
Abstrak: Antioxidant activity is important to protect our body from free radicals. Green vegetables such as broccoli has high content of lutein which can act as an antioxidant. The objective of this study was to isolate and characterize lutein extract of broccoli flowers, and then further evaluated its antioxidant activity by using α,α-diphenyl-β-picrylhydrazyl (DPPH). The extraction used n-hexane as solvent and KOH/ethanol for saponification process. Extracted lutein was characterized with preparative thin layer chromatography (TLC). Four fractions were obtained from preparative TLC and fraction 3 had the same Rf compared with lutein standard. This fraction was further analyzed with Fourier transform infrared (FTIR) spectrophotometer and had similar functional groups with lutein standard. Based on this result, it can be concluded that broccoli flower extract has lutein compound and potential as an antioxidant with 99.321 μg/mL IC50 value.
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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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