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.
Keyword: 

Judul: Potensi Ekstrak Etanol Kulit Batang dan Daun Berenuk (Crescentia cujete L.) sebagai Antibakteri
Abstrak: Berenuk (Crescentia cujete L.) memiliki berbagai senyawa aktif yang dapat berfungsi sebagai antibakteri. Tujuan penelitian ini adalah mengidentifikasi senyawa aktif yang terdapat pada ekstrak etanol kulit batang dan daun berenuk, menentukan aktivitas antibakteri terhadap bakteri S. aureus dan E. coli, dan konsentrasi hambat minimum (KHM) pada bakteri S. aureus. Senyawa aktif pada kedua ekstrak diidentifikasi dengan uji fitokimia. Uji aktivitas antibakteri dilakukan dengan metode difusi cakram dengan konsentrasi bakteri 106 cfu/mL. Penentuan KHM dilakukan dengan metode kontak. Hasil uji fitokimia menunjukkan bahwa ekstrak etanol kulit batang dan daun berenuk mengandung alkaloid, flavonoid, saponin, tanin, dan steroid. Hasil uji aktivitas antibakteri menunjukkan kedua ekstrak memiliki aktivitas penghambatan yang lebih besar terhadap S. aureus dan menghasilkan zona hambat terbesar pada konsentrasi 100%. Persentase penurunan jumlah koloni bakteri pada kedua ekstrak kurang dari 90% sehingga KHM kedua ekstrak terhadap S. aureus belum dapat ditentukan.
Keyword: antibakteri, berenuk, daun, ekstrak etanol, kulit batang

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.
Keyword: