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: Aktivitas antibakteri fraksi aktif daun lidah mertua (Sansevieria trifasciata Prain)
Abstrak: Sansevieria trifasciata Prain is an indigenous plant of South Africa and indicated has an antibacterial activity. The purpose of this study is to evaluate the potential of this speciesas antibacterial to inhibit the activity of Staphylococcus aureus and Escherichia coli using disc diffusion method. Some leaves were extracted using maceration method. The result indicated that crude extract at concentration 1250, 2500, 5000, and 10000 ppm showed no activity against the test bacterial. Steroids, flavonoids, and alkaloids were found in the crude extract. The crude extract was fractionated using column chromatography. Ethyl acetate and chloroform were used as eluent with the best ratio (6:1). The fractionation yield 10 fractions. The fraction were test at concentration 10000, 20000, and 40000 ppm. The antibacterial assay showed there was only 1 fraction active against Gram-positive (S. aureus).
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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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