Judul: Aktivitas antioksidan ekstrak lidah mertua (Sansievieria trifasciata) terhadap 1,1-Difenil-2-Pikrilhidhazil
Abstrak: Lidah mertua merupakan tanaman asli Afrika yang dikenal sebagai tanaman hias yang berfungsi untuk menyerap polutan. Tujuan penelitian ini adalah mengevaluasi potensi antioksidan yang dimiliki lidah mertua dalam menghambat 1,1- difenil-2-pikrilhidrazil (DPPH). Penelitian ini diawali dengan ekstraksi lidah mertua secara maserasi menggunakan pelarut etanol 70%. Rendemen ekstrak kasar 19.43%. Uji fitokimia alkaloid, saponin, steroid, dan flavonoid terhadap ekstrak kasar menunjukkan hasil yang positif. Uji DPPH terhadap ekstrak kasar (IC50 = 2900.52 ppm) dan fraksi air (IC50 = 2072.36 ppm) dari ekstrak kasar menunjukkan aktivitas antioksidan yang lemah dibandingkan kontrol positif vitamin C (IC50 = 6.27 ppm). Uji yang sama terhadap fraksi etil asetat dari ekstrak kasar menunjukkan aktivitas antioksidan yang sedikit lebih baik (IC50 = 696.46 ppm). Penelitian ini menunjukkan bahwa ekstrak daun lidah mertua memiliki aktivitas antioksidan yang rendah.
Keyword: Antioksidan, In vitro, Sanseviera zebrine, Bogor Agricultural University, Institut Pertanian Bogor, IPB

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: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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