Judul: Potensi Antioksidan dan Toksisitas Ekstrak Daun Sansevieria cylindrica
Abstrak: One of the ornamental plants that have antioxidant activity is Sansevieria sp. These plant has many varieties, one of them is Sansevieria cylindrica that alleged to have antioxidant activity. Antioxidant properties of these plants is not known so we need to investigate it. This study aimed to test the antioxidant potency and toxicity of S. cylindrica leaf extract. S.cylindrica leaf was extracted using 80% methanol, ethanol, 80% acetone, and water. Extraction results was evaporated in vacuum to obtain powder rendements (extracted with methanol, ethanol, water) and clod rendement (extracted with acetone). Extract ability as an antioxidant was determined through neutralization of 1.1-diphenyl-2-picrilhidrazil radical (DPPH). The results from the DPPH test was a radical change color from purple to yellow and the absorbance was measured using a UV-Vis spectrophotometer at 514 nm wavelength. Extract that produced the best antioxidant activity was tested for toxicity using the Artemia salina (Brine Shrimp Test, BST). The antioxidant activity of methanol, ethanol, acetone, and water extract respectively is 65.64%, 67.02%, 70.95% and 71.93% at 800 ppm extract concentration. DPPH test of the four solvents did not produced significant differences (p> 0.05). Phytochemical test results showed the presence of flavonoids and tannins that estimated supports antioxidant activity. BST test result of S.cylindrica leaf extracts showed that the LC50 concentration of the extract occurred at 1223.6820 ppm.
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Judul: Uji Aktivitas Antibakteri Fraksi Daun Lidah Mertua (Sansevieria trifasciata)
Abstrak: Sansevieria trifasciata is an indigenous plant of South Africa used in herbal medicine for the treatment of various infectious diseases. The purpose of this study is to evaluate potency of S. trifasciata extracts through in vitro antibacterial test against Grampositive (Staphylococcus aureus) bacteria and Gram-negative (Escherichia coli) bacteria on Mueller-Hinton medium. The plant sample were obtained from research garden at Lodaya Campus, Bogor Agricultural University. The result indicated that methanol crude extract at concentration 10000, 5000, 2500, and 1250 ppm showed no activity against the tested bacteria. Methanol crude extract was fractionated using coloumn chromatography with gradient method. Methanol and chloroform were used as eluent with the best ratio of 9:1. The fractionation yielded 10 fractions. The fractions were tested at concentration 40000, 20000, and 10000 ppm. The antibacterial assay showed there were 2 active fractions for both of the tested bacteria, 5 active fractions against only Gram-positive (S. aureus) and 3 non-active fractions.
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Judul: Estimating Parameter and the Convergence of Parameter Estimator of Poisson Hidden Markov Model
Abstrak: Model hidden Markov terdiri dari sepasang proses stokastik yaitu proses observasi dan proses yang memengaruhi observasi. Proses stokastik yang memengaruhi observasi ini diasumsikan membentuk rantai Markov dan tidak diamati. Model Poisson hidden Markov (MPHM) adalah salah satu model hidden Markov diskret dan proses observasinya jika diketahui proses yang memengaruhinya diasumsikan menyebar Poisson., A hidden Markov model (HMM) consists of a pair of stochastic processes, that is the observation process and process that affected observation. The stochastic process which causes this observation is assumed to form a Markov chain and is not observed. Poisson hidden Markov models (PHMM) is one of the discrete HMM and the observation process given the cause is assumed having a Poisson distribution.
Keyword: Poisson hidden Markov model, Forward-Backward algorithm, Expectation Maximization algorithm