Judul: Optimization of Purslane (Portulaca oleracea) Extraction Solvent for Total Phenolic and Antioxidant Activity Using Simplex Centroid Design
Abstrak: Krokot (Portulaca oleracea) merupakan tanaman gulma yang berpotensi sebagai antioksidan. Potensi ini dikarenakan adanya kandungan berbagai jenis metabolit sekunder pada tanaman tersebut, salah satunya fenolik. Pemilihan pelarut ekstraksi sangat penting dilakukan untuk mendapatkan metabolit yang maksimal. Penelitian ini bertujuan menentukan pelarut atau kombinasi pelarut ekstraksi terbaik untuk mengekstrak tanaman krokot berdasarkan kadar total fenolik (TPC) dan aktivitas antioksidan menggunakan simplex centroid design (SCD). Sampel diekstraksi dengan metode gabungan sonikasi dan maserasi. Rancangan optimasi pelarut dibuat menggunakan Design Expert 13.0 dengan metode SCD. TPC diukur menggunakan metode Folin-Ciocalteu dan aktivitas antioksidan menggunakan metode FRAP. Hasil penelitian menunjukkan pelarut aseton-air memiliki TPC tertinggi sedangkan pelarut aseton-air-metanol menunjukkan nilai FRAP tertinggi. Solusi optimasi pelarut yang didapat yaitu penggunaan air-aseton-etanol dengan rasio berturut-turut adalah 0,342; 0,389; 0,269. Verifikasi solusi optimasi dilakukan secara triplo menghasilkan TPC dengan nilai %RSE sebesar 0,364 dan FRAP dengan nilai %RSE sebesar -19,19. SCD dapat mengoptimalkan pelarut ekstraksi krokot dengan respon kadar total fenolik dan aktivitas antioksidan.
Keyword: antioksidan, fenolik, krokot, optimasi, pelarut

Judul: Optimization Extraction of Total Flavonoid and Antioxidant Capacity of Purslane (Portulaca grandiflora Hook.) using Two-half Factorial Design
Abstrak: Krokot (Portulaca grandiflora Hook.) merupakan tanaman liar yang memiliki potensi sebagai antioksidan. Penelitian bertujuan mengidentifikasi faktor rasio cairan/padatan, suhu, konsentrasi etanol, waktu, dan pH, selama proses ekstraksi krokot yang berkontribusi signifikan terhadap nilai total flavonoid dan kapasitas antioksidan FRAP. Faktor rasio cairan/padatan menunjukan pengaruh paling signifikan (p<0.0001) untuk mengasilkan nilai total flavonoid dan kapasitas antioksidan FRAP. Kadar total flavonoid (TFC) dihitung menggunakan metode AlCl3 dan kapasitas antioksidan menggunakan metode FRAP. Kadar total flavonoid tertinggi terdapat pada perlakuan 14 (22,4262 ± 3,192 mg QE/g BK). Kapasitas antioksidan FRAP tertinggi terdapat pada perlakuan 13 (511,8949 ± 6,030 µmol TE/g BK). Hasil optimasi menunjukan kondisi ekstraksi yang direkomendasikan sebagai solusi kombinasi perlakuan optimum dengan rasio cairan/padatan 100 ml/g, suhu 68°C, konsentrasi etanol 80%, waktu 300 menit dan pH 2 dengan nilai desirability 0,839. Verifikasi solusi optimasi dilakukan secara triplo menghasilkan TFC dengan nilai %RSE 3,349 dan FRAP dengan %RSE sebesar 0,003%. Two-half factorial Design mampu mengoptimalkan proses ekstraksi krokot dengan respon kadar total flavonoid dan kapasitas antioksidan., Purslane (Portulaca grandiflora Hook.) is a wild plant with potential as an antioxidant. This study aimed to identify the factors of liquid/solid ratio, temperature, ethanol concentration, time, and pH during the purslane extraction process, which significantly contributed to total flavonoid value and antioxidant capacity of FRAP. Of all the factors, the liquid/solid ratio showed the most significant effect (p<0.0001) on producing total flavonoid value and antioxidant activity of FRAP. Total flavonoid content (TFC) was calculated using the AlCl3 method, and antioxidant activity using the FRAP method. The highest levels of total flavonoids were found in treatment 14 (22.4262 ± 3.192 mg QE/g DM). The highest antioxidant activity of FRAP was found in Treatment 13 (511.8949 ± 6.030 µmol TE/g DM). The optimization results show the recommended extraction conditions as the optimum treatment combination solution with a liquid/solid ratio of 100 ml/g, temperature of 68°C, 80% ethanol concentration, time of 300 minutes, and pH 2 with a desired value of 0.839. The verification solution was verified in triplicate to produce a TFC with a %RSE value of 3.349% and a FRAP with a %RSE of 0.003%. The two-half factorial design can optimize the purslane extraction process in response to total flavonoid levels and antioxidant activity.
Keyword: antioksidan, ekstraksi, flavonoid, krokot

Judul: Dynamic New Keynesian Model for Unemployment and Inflation Rate.
Abstrak: This paper deals with a scientific analysis of the equilibrium level of hiring, employment and unemployment. The basic model being used is a standard new Keynesian model, which states that utility function depends on consumptions and working hours. Utility maximization refers to a standard labour supply equation, with the marginal cost’s dynamics on new Keynesian model simply reflects movements in real wages and productivity. Furthermore, trade-off between output and inflation stabilization can be considered using the new Keynesian Phillips curve. Dynamic general equilibrium model is a model that can be used to study interactions between market imperfections and nominal rigidities, which is capable of overcoming the main shortcoming of the standard new Keynesian model. In the general equilibrium model there are three groups of the economy agents, namely households, firms and monetary authority. The results of this research science that bargaining processes between firms and workers will yield optimal wage. Increase in labour will cause wages to fall, but the unemployment rate can be reduced. An increase in the firm’s monopoly power will shift the labour demand curve downward, which will reduce the number of workers that firm is willing to hire for any given bargained wage.
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