Judul: Fraksinasi komponen aktif antibakteri ekstrak kulit batang tanaman berenuk (Crescentia cujete L)
Abstrak: The objectives of this research are to determine the most antibacterial active fraction of berenuk stem bark extracts, to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), and to identify phytochemical constituents of the fraction. Preliminary screening of crude methanol extract and all fractionated extracts (n-hexane, ethyl acetate, and aqueous fraction) against Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative) were tested by disc-diffusion assay. The results showed that only methanol extract and its n-hexane and ethyl acetate fractions that could inhibit growth of all tested bacteria, and the most active fraction among all fractionated extract was n-hexane fraction. Fractionation of n-hexane extract using silica gel column chromatography (gradient elution) produced 10 fractions. All of the fractions showed antibacterial activities, and the most active was fraction II with percentage towards S. aureus was 35.86% and E. coli was 63.01%. The MIC towards S. aureus and E. coli were 0.2 and 0.1 mg/mL, and the MBC for both of bacteria were 10 and 5 mg/mL, respectively. Phytochemical screening showed that steroid and alkaloid were the active constituents of the fraction II. This result concludes that steroids and alkaloids from berenuk stem bark are potential as antibacterial agents.
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Judul: Aktivitas Antibakteri Fraksi Etanol Kulit Batang Tumbuhan Berenuk (Crescentia cujete L.).
Abstrak: Berenuk termasuk salah satu tumbuhan yang dapat dijadikan obat herbal. Kulit batang berenuk mempunyai kemampuan sebagai antibakteri. Penelitian ini bertujuan menentukan aktivitas antibakteri kulit batang berenuk pada fraksi n-heksana, diklorometana, etil asetat dan air menggunakan metode difusi agar dan metode kromatografi lapis tipis (KLT) bioautografi. Uji aktivitas antibakteri difusi agar menunjukkan bahwa fraksi air mampu menghambat pertumbuhan bakteri Escherichia coli sedangkan fraksi diklorometana dan fraksi etil asetat mampu menghambat pertumbuhan bakteri Staphylococcus aureus. Fraksi diklorometana memiliki aktivitas antibakteri pada KLT Bioautografi pada Rf 0.88, 0.84, dan 0.78 yang mampu menghambat pertumbuhan bakteri S. aureus.
Keyword: antibakteri, berenuk, bioautografi

Judul: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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