Judul: Aktivitas Antioksidan, Kadar Fenolik, dan Flavonoid Tumbuhan Suruhan (Peperomia pellucida L. Kunth)
Abstrak: Suruhan (Peperomia pellucida L.Kunth) is the bush had widespread in Indonesia and has efficacy as arthritis pain relief, anticancer, and antibacterial. The aim of this study was testing the activity of suruhan’s herb extracts as natural antioxidants and measured the total phenolic and flavonoid content in suruhan. The sample used in the form of 70% ethanol extract and aqueous extract of the suruhan. The extract obtained by maceration method and tested antioxidants with DPPH method and then tested the content of total phenolic and flavonoid extracts and analyzed the correlation of these compounds to antioxidant activity. The yield of 70% ethanol extract was 20.43 ± 3.33% whereas the yield of aqueous extract was 10.03 ± 2.85%. Both of extract has produced the antioxidant activity of free radical DPPH capture. IC50 values of aqueous extract of 256.67 ± 21.65 ppm, followed by ethanol extract of 297.79 ± 17.75 ppm. Total phenolic content of aqueous extract was 755.79 ± 65.87 mgTAE/g and ethanol extract was 622.46 ± 179.43 mg TAE/g. Total flavonoid content of ethanol extract was 4.058 ± 0.352 mg QE/g and aqueous extract was 0.67 ± 0.352 mg QE/g extract for aqueous. The phenol content have linier correlation with their antioxidant activity but the flavonoid content didn’t have correlation with antioxidant activity.
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Judul: Aktivitas Antioksidan, Kadar Fenolik, dan Flavonoid Total Tumbuhan Suruhan (Peperomia pellucida L.Kunth)
Abstrak: Suruhan (Peperomia pellucida L. Kunth) merupakan tumbuhan semak yang tersebar luas di seluruh wilayah Indonesia dan memiliki khasiat untuk meredakan nyeri rematik, sebagai antikanker, dan antibakteri. Penelitian ini bertujuan untuk menguji aktivitas ekstrak herba suruhan sebagai antioksidan alami dan mengukur kadar fenolik dan flavonoid total dalam suruhan. Sampel yang digunakan berupa ekstrak etanol 70% dan ekstrak air dari herba suruhan. Ekstrak didapat dengan metode maserasi dan dilakukan uji antioksidan dengan metode DPPH kemudian dilakukan uji kandungan fenolik dan flavonoid total ekstrak serta dianalisis korelasi kedua senyawa ini terhadap aktivitas antioksidannya. Rendemen yang dihasilkan oleh ekstrak etanol 70% sebesar 20.43 ± 3.33% sedangkan rendemen ekstrak air sebesar 10.03 ± 2.85%. Kedua ekstrak menunjukkan aktivitas antioksidan dalam penangkapan radikal bebas DPPH. Nilai IC50 ekstrak air sebesar 256.67 ± 21.65 ppm yang diikuti oleh ekstrak etanol sebesar 297.79 ± 17.75 ppm. Kandungan fenolik ekstrak air sebesar 755.79 ± 65.87 mg TAE/g dan ekstrak etanol sebesar 622.46 ± 179.43 mg TAE/g. Kandungan flavonoid total ekstrak etanol sebesar 4.058 ± 0.352 mg QE/g dan ekstrak air sebesar 0.67 ± 0.352 mg QE/g. Kandungan total fenol berkorelasi linier dengan aktivitas antioksidan tetapi aktivitas antioksidan tidak memiliki korelasi dengan flavonoid.
Keyword: Suruhan, Antioxidant, Flavonoid, Phenolic

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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