Judul: Total Phenolic Content and Antioxidant Capacity of Purslane (Portulaca oleracea L.) as Affected by Different
Abstrak: Krokot (Portulaca oleracea L.) merupakan tanaman yang telah terbukti mengandung berbagai macam senyawa bioaktif. Penelitian ini bertujuan mengukur dan menganalisis pengaruh jenis pelarut ekstraksi terhadap kadar fenolik total serta kapasitas antioksidan pada tanaman krokot. Sampel diekstraksi menggunakan gabungan metode ekstraksi sonikasi-maserasi dengan lima jenis pelarut (etanol p.a, metanol p.a, aseton p.a, etil asetat p.a, air). Hasil penelitian menunjukkan bahwa kadar fenolik total tertinggi dihasilkan oleh ekstrak air (2.78 mg GAE/g BK), sementara kadar terendah dihasilkan oleh ekstrak etil asetat (0.60 mg GAE/g BK). Kapasitas antioksidan pada berbagai metode uji (CUPRAC, FRAP, ABTS, DPPH) memiliki nilai signifikansi berbeda-beda berdasarkan hasil uji One-Way ANOVA (Analysis of Variance) dan uji lanjut Tukey HSD. Hasil korelasi Pearson positif sangat kuat ditunjukkan oleh kadar fenolik total dengan kapasitas antioksidan metode ABTS (r = 0.9145) dan FRAP (r = 0.9452). Penggunaan pelarut yang memiliki tingkat polaritas tinggi (air, metanol, etanol) direkomendasikan untuk mengekstrak senyawa fenolik dari aerial parts tanaman krokot maupun untuk isolasi, karakterisasi, serta pemanfaatan lebih lanjut., Purslane (Portulaca oleracea L.) is a plant that has been proven to contain various bioactive compounds. This study aim to measure and analyze the effect of extraction solvent type on total phenolic content and antioxidant capacity in purslane plants. Samples were extracted using a combined sonication-maseration extraction method with five types of solvents (ethanol p.a, methanol p.a, acetone p.a, ethyl acetate p.a, water). The results showed that the highest total phenolic content was produced by water extract (2.78 mg GAE/g BK), while the lowest level was produced by ethyl acetate extract (0.60 mg GAE/g BK). Antioxidant capacity in various test methods (CUPRAC, FRAP, ABTS, DPPH) has different significance values based on the results of One-Way ANOVA (Analysis of Variance) test and Tukey HSD. Very strong positive Pearson correlation results were shown by total phenolic content with antioxidant capacity of ABTS (r = 0.9145) and FRAP (r = 0.9452). The use of solvents that have a high level of polarity (water, methanol, ethanol) is recommended to extract phenolic compounds from aerial parts of purslane plants as well as for isolation, characterization, and further utilization.
Keyword: antioxidant, phenolic, purslane, solvent

Judul: Total Phenolic, Flavonoid, and Antioxidant Activity of Purslane Flower Extract (Portulaca grandiflora Hook.) Optimized Using Simplex-Centroid Design
Abstrak: Krokot (Portulaca grandiflora Hook.) memiliki kemampuan sebagai antioksidan karena kandungan metabolit sekunder seperti senyawa fenolik dan flavonoid yang dimiliki, salah satunya pada bagian bunganya. Kandungan fenolik dan flavonoid yang terekstrak serta nilai aktivitas antioksidan dapat dipengaruhi oleh penggunaan pelarut ekstraksi. Penelitian ini bertujuan menentukan pelarut terbaik untuk ekstraksi bunga krokot menggunakan microwave-assisted extraction berdasarkan kadar total fenolik (TPC), flavonoid (TFC), serta aktivitas antioksidan (metode DPPH dan FRAP). Pelarut optimal yang direkomendasikan oleh piranti lunak Design Expert menggunakan metode simplex-centroid design (SCD) adalah campuran aseton 41% dan metanol 59%. Hasil penelitian dinyatakan sesuai dengan nilai prediksi berdasarkan uji verifikasi, dengan respon TPC sebesar 3,599 mg GAE/g bobot basah, TFC sebesar 1,796 mg QE/g bobot basah, dan aktivitas antioksidan sebesar 0,669 μmol TE/g bobot basah (DPPH) serta 9,231 μmol TE/g bobot basah (FRAP) dengan nilai desirability sebesar 0,712. Metode SCD terbukti dapat mengoptimalkan pelarut ekstraksi bunga krokot dengan respon TPC, TFC, dan aktivitas antioksidan., Purslane (Portulaca grandiflora Hook.) has the ability as an antioxidant due to the presence of secondary metabolites such as phenolic compounds and flavonoids, one of which is found in its flowers. The extracted phenolic and flavonoid contents, as well as the antioxidant activity, can be affected by the use of extraction solvent. This study aimed to determine the best solvent for extracting the flowers of purslane using microwave-assisted extraction based on the total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities (DPPH and FRAP method). The optimal solvent determined by the Design Expert software using the simplex-centroid design (SCD) method is a mixture of 41 % acetone and 59% methanol. The research results obtained align with the predicted values based on verification tests, yielding TPC of 3,599 mg GAE/g fresh weight, TFC of 1,796 mg QE/g fresh weight, and antioxidant activity of 0,669 μmol TE/g fresh weight (DPPH) and 9,231 μmol TE/g fresh weight (FRAP), with a desirability value of 0,712. SCD method has proven to optimize the extraction solvent for purslane flower in response to TPC, TFC, and antioxidant activity.
Keyword: antioxidant, flavonoid, optimization, phenolic, purslane

Judul: Analysis of Unequal Income Distribution with Cobb-Douglas Production Function
Abstrak: This paper studies the economic growth model by Moav (2002). Moav model shows the existence of unequal income distribution between low-income with high-income community. That kind of unequal income distribution is caused by uneven distribution of income. On this Moav model, there is one area called the threshold. Threshold becomes a benchmark to determining whether a society is categorized into low- or high- income community. The production function used in this paper is the Cobb-Douglas function. The dynamics of this model is described as difference equation of low-income, threshold, and high-income community. Simulation study on the model is carried out using Maple 13 and Mathematica 7.0 software. Overall, from the observed case, high-income community will reach a stable condition earlier, followed by the threshold, and then the low-income community.
Keyword: