Judul: Optimization of Methanol Consentration and Time for Total Phenolics, Total Flavonoids, and Antioxidant  Capacity of Temulawak using Microwave Assisted Extraction Method
Abstrak: Temulawak (Curcuma xanthorrhiza Roxb.) merupakan tanaman obat asli Indonesia yang berpotensi sebagai antioksidan karena mengandung fenolik dan flavonoid. Penelitian ini bertujuan menentukan konsentrasi metanol dan waktu ekstraksi optimum serta memperoleh model sistem dari kadar fenolik total, flavonoid total, dan kapasitas antioksidan simplisia temulawak menggunakan response surface methodology. Sampel diekstraksi dengan metode microwave assisted extraction. Pengolahan data menggunakan aplikasi Design Expert 13.0 dan SPSS IBM. Hasil penelitian menunjukkan bahwa model linear merupakan hasil paling optimum untuk memprediksi semua variabel respon. Hasil verifikasi model menunjukkan kombinasi konsentrasi metanol dan waktu ekstraksi terpilih adalah 100,00% dan 2,722 menit. Verifikasi optimum dari 2 faktor tersebut menghasilkan nilai aktual respon TPC sebesar 14,555 mg GAE/g DW; TFC sebesar 39,257 mg QE/g DW; DPPH sebesar 1,352 µmol TE/g DW; dan FRAP sebesar 61,269 µmol TE/g DW. Respon aktual dari kombinasi konsentrasi pelarut metanol dan waktu ekstraksi optimum terpilih memenuhi nilai verifikasi dengan nilai desirability 84%., Temulawak (Curcuma xanthorrhiza Roxb.) is a medicinal plant native to Indonesia has potential as an antioxidant because it contains phenolics and flavonoids. This study aimed to determine the methanol concentration and extraction time for the extraction of temulawak and to obtain a system model of total phenolic, total flavonoids, and antioxidant capacity, utilizing response surface methodology. Data processing using the Design Expert 13.0 and IBM SPSS. Sample were extracted using the microwave assisted extraction method. The research showed that the linear model is the most optimal result for predicting all response variables. The model verification results show that the selected combination of methanol concentration and extraction time is 100,00% and 2,722 minutes. Verification of these 2 factors resulted in an actual TPC response value of 14,555 mg GAE/g DW; TFC of 39,257 mg QE/g DW; DPPH and FRAP was 1,352 and 61,269 µmol TE/g DW. The actual response of the selected combination optimum, meets the verification value with a desirability of 84%.
Keyword: antioxidant, flavonoid, optimization, phenolic, temulawak

Judul: Optimasi pH dan Konsentrasi Etanol Terhadap Polifenol  dan Antioksidan Temulawak dengan Microwave Assisted Extraction
Abstrak: Rimpang temulawak (Curcuma xanthorrhiza) merupakan tanaman yang berpotensi sebagai antioksidan. Potensi ini disebabkan adanya kandungan senyawa aktif seperti fenolik dan flavonoid. Faktor pada proses ekstraksi penting diperhatikan untuk mendapatkan senyawa aktif yang maksimal. Penelitian ini bertujuan mengoptimasi kandungan fenolik, flavonoid, dan kapasitas antioksidan rimpang temulawak melalui variasi pH (2, 4, 6, 8) dan konsentrasi pelarut etanol (30%, 50%, 70%, 96%). Sampel diekstraksi dengan metode Microwave. Rancangan optimasi dibuat menggunakan Design Expert 13 dengan metode Response Surface Methodology (RSM). TPC diukur menggunakan metode Folin-Ciocalteu, TFC menggunakan metode Aluminium Klorida, dan kapasitas antioksidan menggunakan metode FRAP dan DPPH. Konsentrasi etanol 50% sampai 96% dengan pH 2 sampai 4 menghasilkan metabolit dan antioksidan yang tinggi. Solusi optimasi yang didapat terdapat pada kombinasi etanol 77% dan 96% dengan pH 3,2 dan 4. Verifikasi dilakukan dengan kombinasi konsentrasi 96% dan pH 3,96 menghasilkan TFC dan antioksidan FRAP dengan nilai %RSE sebesar -0,291 dan 0,324. Nilai %RSE dibawah 10% memberikan hasil model yang ideal dan dapat diaplikasikan., Java turmeric rhizome (Curcuma xanthorrhiza) was a plant that has potential as an antioxidant. This potential is due to the content of active compounds such as phenolics and flavonoids. Factors in the extraction process are important to consider to ensure the maximum production of active compounds. This research aimed to optimize the phenolic content, flavonoids, and antioxidant capacity of Java turmeric rhizome by varying pH (2, 4, 6, 8) and ethanol solvent concentration (30%, 50%, 70%, 96%). Samples were extracted using the Microwave method. The optimization design was created using Design Expert 13 with the Response Surface Methodology (RSM) method. TPC was measured using the Folin-Ciocalteu method, TFC using the Aluminum Chloride method, and antioxidant capacity using the FRAP and DPPH methods. Ethanol concentrations of 50% to 96% (in range) with a pH of 2 to 4 produce high levels of metabolites and antioxidants. The optimization solution obtained was a combination of 77% and 96% ethanol with pH 3,2 and 4. Verification was carried out with a combination of 96% concentration and pH 3,96 to produce TFC and antioxidants FRAP with a %RSE value of -0.291 and 0,324. %RSE values below 10% provided ideal and applicable model results.
Keyword: antioksidan, MAE, optimasi, RSM, temulawak

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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