Judul: Senyawa Fitokimia dan Sitotoksisitas Ekstrak Daun Surian (Toona sinensis) Terhadap Sel Vero dan MCF-7
Abstrak: The compounds of surian leaves possess a wide range of pharmacology activity, such as antioxidant and anticancer. The research aimed to analyze phytochemical compounds and cytotoxicity of surian leaves extracts against vero and MCF-7 cells line. Extraction of surian leaves was performed with some solvents, those were water, ethanol 70%, ethyl acetate, and n-hexane. The results showed that highest extracts yield obtained from ethanol 70% followed by water, ethyl acetate, and n-hexane extracts yield were 34.85%, 33.54%, 6.38%, and 1.31% respectively. Surian leaves extracts presence phytochemical compounds of alkaloid, triterpenoid, flavonoid, tanin, phenol, steroid. Highest total phenolic equivalent of gallic acid (GAE) obtained from etanol 70% extracts (500.30 mg GAE/g extract) followed by water (465.30 mg GAE/g extract), ethyl acetat (192.80 mg GAE/g extract), and n-hexane extracts (109.30 mg GAE/g extract). Total flavonoid equivalen of quersetin (QE) water, etanol 70%, ethyl acetat, and n-hexana extracts were 92.10, 62.96, 23.43, dan 12.70 mg QE/g extracts respectively. Results of cytotoxicity assay showed surian leaves extracts were not toxic on vero cells with IC50 value 463.03 (water extract), 197.88 (ethanol 70% extract), 121.09 (ethyl acetat extract), and 217.43 ppm (n-hexane extract). Surian leaves extracts had no anticancer potency against MCF-7 cells with IC50 value of all extracts more than 100 ppm. Based National Cancer Institute (NCI), this value showed low cytotoxicity of surian leaves extracts against MCF-7 cells.
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Judul: Kandungan Fenolik dan Flavonoid Total serta Aktivitas Antioksidan Ekstrak Daun Surian (Toona sinensis).
Abstrak: Tanaman surian diketahui memiliki kandungan senyawa fenolik dan flavonoid yang berfungsi sebagai antioksidan. Penelitian ini bertujuan untuk menguji aktivitas antioksidan, serta mengukur kandungan total fenolik dan flavonoid esktrak daun surian. Aktivitas antioksidan ditentukan dengan metode DPPH (1,1-diphenil-2-picrylhydrazil) dan daya reduksi. Hasil penelitian menunjukkan ekstrak etanol 70% daun surian memiliki kandungan fenolik dan flavonoid total sebesar 225.05 μg GAE/mg dan 38.41 μg QE/mg ekstrak. Hasil ini lebih tinggi dibandingkan ekstrak air yang sebesar 218.79 μg GAE/mg dan 20.00 μg QE/mg ekstrak. Aktivitas antioksidan ekstrak etanol 70% daun surian dinyatakan dalam bentuk IC50, dengan nilai 16.45 μg/mL pada DPPH dan 44.65 μg/mL pada daya reduksi. Semakin kecil nilai IC50, semakin besar aktivitas antioksidan. Nilai IC50 ekstrak etanol 70% lebih tinggi dibandingkan ekstrak air yang sebesar 142.28 μg/mL pada DPPH dan 60.15 μg/mL pada daya reduksi. Semakin besar kadar fenolik dan flavonoid total, semakin tinggi aktivitas antioksidannya.
Keyword: antioksidan, daun surian, fenolik, flavonoid

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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