Judul: Total Flavonoid, Total Fenolik dan Aktivitas Antioksidan Ekstrak Metanol Temulawak yang Dibudidayakan dengan Kombinasi Pupuk N,P, dan K
Abstrak: Temulawak (Curcuma xanthorriza roxb.) dilaporkan mengandung senyawa fitokimia dan aktivitas antioksidan tinggi. Tujuan penelitian ini adalah mengukur total flavonoid, total fenolik dan aktivitas antioksidan ekstrak temulawak yang dibudidaya dengan kombinasi pupuk NPK menggunakan metode DPPH dan ABTS. Sampel diekstraksi menggunakan maserasi bertingkat dan dievaporasi dengan vacuum evaporator. Kandungan total flavonoid tertinggi yaitu sampel dengan pupuk NPK sebesar 50±23,81 mg QE/bobot kering dan kandungan total fenolik tertinggi juga terdapat sampel dengan pupuk NPK sebesar 34,67±3,79 mg GAE/bobot kering. Uji antioksidan metode DPPH menunjukkan sampel dengan pupuk NK memiliki aktivitas antioksidan tertinggi sebesar 169,67±8,5 µmol TE/g bobot kering. Hasil berbeda pada metode ABTS pada sampel dengan pupuk NPK sebesar 261,67±29,69 µmol TE/g bobot kering. Pupuk NPK berpotensi sebagai pupuk terbaik untuk meningkatkan kandungan metabolit sekunder dan aktivitas antioksidan temulawak., Temulawak (Curcuma xanthorriza roxb.) is reported to contain phytochemicals and high antioxidant activity. The purpose of this reasearch was to measure the flavonoid content, phenolic content, and the antioxidant activity of methanol extract of temulawak cultivated by using NPK fertizer combination. The samples were extracted with graded maceration and evaporated with vacuum evaporator. The extracts were subjected to total flavonoid, total phenolic, and antioxidant activity assays. The antioxidant activity was measured using the DPPH and ABTS methods. The highest total flavonoid content was sample from NPK fertilizer of 50±23,81 mg QE/dry weight, and the highest phenolic content was from NPK fertilizer of 34,67±3,79 mg GAE/dry weight. The antioxidant test using the DPPH method showed that the extract from NK fertilizer had the highest antioxidant activity of 169,67±8,5 µmol TE/dry weight. Different results were obtained in ABTS method, was found in extract with NPK fertilizer is 261,67±29,69 µmol TE/g dry weight. NPK fertilizer gave the best result for increase secondary metabolites and antioxidant activity of temulawak.
Keyword: antioxidant, NPK, temulawak, flavonoid, phenolics

Judul: Produktivitas Kurkuminoid dan Aktivitas Antioksidan Temulawak (Curcuma xanthorrhiza Roxb.) Dibudidaya dengan Kombinasi Pupuk N, P, dan K
Abstrak: Temulawak (Curcuma xanthorrhiza Roxb.) termasuk tanaman obat yang mengandung senyawa kurkuminoid dan memiliki aktivitas antioksidan. Penelitian ini bertujuan menentukan kombinasi pupuk N, P, K terbaik berdasarkan kadar senyawa kurkuminoid dan aktivitas antioksidan pada rimpang temulawak, serta menentukan korelasi antara keduanya. Kadar kurkuminoid ditentukan dengan High Performance Liquid Chromatography (HPLC), sedangkan aktivitas antioksidan diukur menggunakan metode Ferric Reducing Antioxidant Power (FRAP) dan Cupric ion Reducing Antioxidant Capacity (CUPRAC). Kadar kurkuminoid tertinggi terdapat pada perlakuan K, P, NK, dan NPK dengan nilai masing-masing 8,61; 8,50; 7,99; dan 7,04 mg/g bobot kering. Aktivitas antioksidan tertinggi metode FRAP terdapat pada pemupukan kombinasi NK dan NPK dengan nilai 43,24 dan 41,76 µmol TE/g bobot kering, sedangkan pada metode CUPRAC terdapat pada pemupukan kombinasi NPK sebesar 307,11 µmol TE/g bobot kering. Aktivitas antioksidan berbanding lurus dengan kandungan kurkuminoid berdasarkan uji korelasi. Pupuk NPK merupakan kombinasi pupuk terbaik dalam meningkatkan kandungan kurkuminoid dan aktivitas antioksidan temulawak., Temulawak (Curcuma xanthorrhiza Roxb.) is a medicinal plant that contains curcuminoid compounds and has antioxidant activity. This study aims to determine the best combination of N, P, K fertilizers based on levels of curcuminoid compounds and antioxidant activity in temulawak rhizome, and determine correlation between them. The curcuminoid level was determined by HPLC, while the antioxidant activity was measured using the FRAP and CUPRAC methods. The highest curcuminoid levels were found in the K, P, NK, and NPK treatments with a value of 8,61; 8,50; 7,99; and 7,04 mg / g dry weight, respectively. The highest antioxidant activity of the FRAP method was found in the combination of NK and NPK fertilization with values of 43,24 and 41,76 µmol TE / g dry weight, while in the CUPRAC method was found in NPK combination fertilization with value 307,11 µmol TE / g dry weight. Antioxidant activity was directly proportional to curcuminoid content based on correlation test. NPK fertilizer is the best combination to increase the curcuminoid content and antioxidant activity of Curcuma xanthorrhiza.
Keyword: antioxidant, curcuminoid, java turmeric, NPK fertilizer

Judul: Bifurkasi Hopf pada siklus bisnis IS-LM tanpa dan dengan waktu tunda
Abstrak: One of business cycle models in dynamical economics is the IS-LM business cycle model with time delay, where the time delay lies in stock capital variables. It is a time delay between the existence of stock capital and the time to get ready to invest. In a model without time delay, changing the parameter of investment rate on income could affect the system stability. On the other hand, in a model with time delay, there exists critical time delay changing the system stability. This shows limit cycle, which can be concluded that Hopf bifurcation occurs
Keyword: Bogor Agricultural University (IPB), time delay, Hopf bifurcation, business cycle model