Judul: Trypsin Inhibitory Activity by Wungu Leaf Extract (Graptophyllum pictum (L.) Griff.) In Vitro
Abstrak: Tanaman wungu (Graptophyllum pictum (L.) Griff.) termasuk salah satu tanaman obat tradisional Indonesia. Daun dari tanaman wungu memiliki metabolit sekunder yang berpotensi sebagai anti obesitas dengan menginhibisi enzim tripsin sehingga efek yang dihasilkan akan lebih optimal. Penelitian ini bertujuan menentukan aktivitas penghambatan enzim tripsin oleh ekstrak daun wungu sebagai anti obesitas. Penelitian ini dilakukan dengan uji kadar air dengan metode gravimetri menghasilkan kadar air sebesar 9.38±0.22% dan kadar abu sebesar 12.54 ± 2.48%. Ekstraksi dilakukan dengan metode maserasi menggunakan pelarut air, etanol, dan etil asetat dengan nilai rendemen berturut-turut sebesar 0.96 ± 0.37%, 0.65 ± 0.26%, dan 0.03 ± 0.02%. Uji aktivitas protein enzim tripsin menggunakan ekstrak dengan konsentrasi 0, 500, 1000, dan 2000 ppm menunjukkan nilai IC50 sebesar 2846.36 untuk ektrak air, 2822.25 untuk ekstrak etanol, dan 1915.25 untuk ekstrak etil asetat. Simpulan penelitian ini yaitu ekstrak daun wungu memiliki potensi untuk dikembangkan sebagai salah satu bahan aktif anti obesitas., The wungu plant (Graptophyllum pictum (L.) Griff.) is one of Indonesia's traditional medicinal plants. The leaves of the Wungu plant have secondary metabolites that have the potential to act as anti-obesity by inhibiting the trypsin, so that the resulting effect will be more optimal. This study aims to determine the inhibitory activity of the trypsin by Wungu leaf extract as an anti-obesity agent. This research was carried out by testing the water content using the gravimetric method to produce a moisture content of 9.38 ± 0.22% and an ash content of 12.54 ± 2.48%. Extraction was carried out by maceration method using water, ethanol and ethyl acetate solvents with yield values of 2.87%, 1.94% and 0.10% respectively. Trypsin protein enzyme activity test using extracts with concentrations of 0, 500, 1000, and 2000 ppm showed IC50 values of 2846.36 for the water extract, 2822.25 for the ethanol extract, and 1915.25 for the ethyl acetate extract. The conclusion of this study is that Wungu leaf extract has the potential to be developed as an anti-obesity active ingredient.
Keyword: anti-obesity, trypsin, wungu leaves

Judul: Aktivitas Inhibisi Enzim α-Glukosidase dan Antioksidan dari Ekstrak Etanol Daun Wungu (Graptophyllum pictum (L.) Griff) dan Partisinya
Abstrak: Wungu leaves (Graptophyllum pictum (L.) Griff) is a plant that is widely used in treating a variety of ailments, including diabetes and known to contain phenolic compounds that have antioxidant activity. The purpose of this study was to determine the inhibition of the enzyme α-glucosidase and antioxidant activities of ethanol extracts and fractions of diethyl ether, ethyl acetate, and butanol from wungu leaves (Graptophyllum pictum (L.) Griff) by in vitro studies. Extraction of wungu leaves was done by maceration and the fractination was done through liquid-liquid extraction. Results showed that ethanol extracts and its fraction have no inhibitory activity toward α-glucosidase, but it was potentially as antioxidant through inhibition of radical DPPH. Ethyl acetate fraction (500 ppm) can capture the DPPH radical 74.105% with IC50 values of 68.11 ppm which is the highest antioxidant activity and is followed by the fraction of butanol, ethanol, and diethyl ether.
Keyword: DPPH, wungu leaves, α-glucosidase, antioxidant, antidiabetic

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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