Judul: Penapisan Antibakteri dan Inhibitor Topoisomerase I dari Xylocarpus granatum
Abstrak: Plants having biological activites have been studied intensively due to the demand of natural medicines. One of coastal plants having antibacterial and cytotoxic activity is Xylocarpus granatum. This paper presented antibacterial and topoisomerase I inhibitor activities of Xylocarpus granatum extract. The antibacterial activity was assyed using agar diffusion method and topoisomerase I inhibitor activity was carried out using topoisomerase drug screening kit from TopoGen. The results showed the methanol crude extract of Xylocarpus granatum’s root, stem, seed, and fruit inhibited the growth of non-clinical E.coli and S.aureus. They also inhibited topoisomerase I at concentration of 50 :g/ml, except hexane crude extract. The MIC of stem methanol extract against topoisomerase I was 25 :g/ml. Stem methanol extract contained alkaloid, flavonoid, and tanin. In addition, seed extract contained saponin. The alkaloid, flavonoid, and tanin inhibited non-clinical E. coli, furthermore flavonoid compound described antibacterial activity against clinical isolates of S. aureus and E. coli.
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Judul: Ability of Xylocarpus granatum’s endophytic actinobacteria to inhibit the growth of Propionibacterium acnes
Abstrak: Propionibacterium acnes merupakan salah satu bakteri patogen penyebab jerawat pada manusia. Buah Xylocarpus granatum secara tradisional telah digunakan sebagai bedak anti jerawat oleh masyarakat di Luwu, Sulawesi Selatan. Keberadaan aktinobakteri endofit di dalam jaringan X. granatum dapat berpotensi menghasilkan metabolit sekunder sebagai antibakteri yang penting untuk pengobatan jerawat dengan bahan alami. Penelitian ini bertujuan mengkaji aktivitas supernatan dan ekstrak etil asetat aktinobakteri endofit X. granatum sebagai antibakteri P. acnes. Sebanyak 24 isolat aktinobakteri endofit X. granatum dari koleksi Laboratorium Mikrobiologi, Departemen Biologi, FMIPA, IPB diremajakan pada media International Streptomyces Project 4 (ISP4). Karakterisasi morfologi menunjukkan kelima isolat memiliki ciri-ciri genus Streptomyces dengan tipe rantai spora Rectus Flexibilis. Penapisan aktivitas antibakteri dari supernatan aktinobakteri dilakukan terhadap P. acnes. Aktivitas inhibisi pertumbuhan P. acnes diindikasikan dengan terbentuknya zona bening di sekeliling cakram kertas berdiameter 6 mm. Sebanyak 14 dari 24 supernatan isolat mampu menghasilkan zona bening dengan diameter berkisar antara 1,00-7,00 mm. Isolat XGS3, XGS4, XGS6, XGS7, dan XGS8 yang menghasilkan zona bening dengan diameter antara 6,50-7,00 mm selanjutnya diekstraksi dengan pelarut etil asetat, kemudian diuji kembali kemampuan inhibisinya terhadap P. acnes. Ekstrak etil asetat isolat XGS8 konsentrasi 1000 ppm memiliki diameter zona bening terbesar diantara kelima isolat terpilih, yaitu sebesar 7,50 mm. Konsentrasi Hambat Minimum (KHM) isolat XGS3, XGS4, dan XGS8 yaitu pada konsentrasi 500 ppm, sedangkan KHM isolat XGS6 dan XGS7 yaitu pada konsentrasi 750 ppm. Data tersebut menunjukkan bahwa isolat XGS3, XGS4, XGS6, XGS7, dan XGS8 dapat menghambat pertumbuhan P. acnes.
Keyword: acne vulgaris, actinobacteria, antibacterial, endophytes, Xylocarpus granatum

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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