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: 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: 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.
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