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.
Keyword: 

Judul: Xylocarpus granatum Endophytic Actinobacteria: Presence and Activity of Antioxidants
Abstrak: Xylocarpus granatum menghasilkan berbagai senyawa bioaktif dengan aktivitas biologis yang beragam, salah satunya sebagai antioksidan. Aktinobakteri endofit juga dapat menghasilkan senyawa bioaktif. Penelitian ini bertujuan untuk mengetahui keberadaan aktinobakteri endofit X. granatum dan mengetahui aktivitas antioksidannya. Metode penelitian diawali dengan isolasi aktinobakteri endofit dari buah, biji, dan daun menggunakan media selektif Humic acid (HV). Selanjutnya dilakukan karakterisasi isolat yang diperoleh menggunakan empat media berbeda yaitu YSA, ISP2, ISP3, dan ISP4. Aktivitas antioksidan dari supernatant aktinobakteri dan ekstrak etil asetat aktinobakteri dilakukan menggunakan metode DPPH. Hasil penelitian menunjukkan bahwa dari X. granatum diperoleh 15 isolat aktinobakteri endofit dari buah, biji, dan daun. Isolat aktinobakteri endofit X. granatum menunjukkan perbedaan warna pada miselium aeria dan miselium substrat, serta perbedaan penataan rantai spora. Supernatan XGF11, XGF12, dan XGF4 menghasilkan aktivitas antioksidan tertinggi yaitu: 57.30%, 49.77%, dan 41.90% penghambatan. Kapasitas antioksidan ekstrak etil asetat XGF12 adalah 501.60 μg AEAC/mg ekstrak, 465.47 μg AEAC/mg ekstrak untuk ekstrak etil asetat XGF11, dan 455.53 μg AEAC/mg ekstrak untuk ekstrak etil asetat XGF4. Ekstraksi DNA aktinobakteri endofit dilakukan berdasarkan Presto Mini gDNA Bacteria Kit. Berdasarkan hasil analisis gen 16S rRNA, isolat XGF11 dan XGF12 menunjukkan kemiripan masing-masing 99.42% dan 99.16% dengan Streptomyces xylanilyticus SR2-123 dan XGF4 memiliki kemiripan 99.82% dengan Brevibacterium sediminis FXJ8.269., Xylocarpus granatum produces various bioactive compounds with diverse biological activities, one of them as an antioxidant. Endophytic actinobacteria can also produce bioactive compounds. This study aimed to explore the existence of the endophytic actinobacteria of X. granatum and determine its antioxidant activity. The research method begins with the isolation of endophytic actinobacteria from fruits, seeds, and leaves using selective media Humic Acid (HV). Furthermore, characterizing the obtained isolates using four different media, namely YSA, ISP2, ISP3, and ISP4. Measured antioxidant activity for actinobacterial supernatants and actinobacterial ethyl acetate extracts using the DPPH method. The results showed that from X. granatum, 15 isolates of endophytic actinobacteria were obtained from fruit, seeds, and leaves. Endophytic actinobacteria isolates from X. granatum showed different colors of aerial mycelium, substrate mycelium, and spore chain type. XGF11, XGF12, and XGF4 isolates produced high antioxidant activity of the supernatant; 57.30%, 49.77%, and 41.90% inhibition, respectively. The antioxidant capacity of XGF12 ethyl acetate extract was 501.60 μg AEAC/mg extract and 465.47 μg AEAC/mg extract for XGF11 ethyl acetate extract. DNA extraction and 16S rRNA amplification from endophytic actinobacteria X. granatum according to Presto Mini gDNA Bacteria Kit Protocol. Based on 16S rDNA gene analysis, isolates XGF12 and XGF11 showed 99.16% and 99.42% similarities with Streptomyces xylanilyticus, respectively. Meanwhile, XGF4 showed to have 99.82% similarities with Brevibacterium sediminis.
Keyword: Keragaman, DPPH, Endofit, Ekstrak etil asetat, 16S rRNA, Diversity, endophytes, ethyl acetate extract

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: