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: Pengaruh Variasi Pelarut dan Waktu Ekstraksi Rimpang Temulawak terhadap Total Fenolik, Flavonoid, dan Aktivitas Antioksidan
Abstrak: Temulawak (Curcuma xanthorrhiza) mengandung senyawa metabolit sekunder seperti fenolik dan flavonoid yang berpotensi sebagai antioksidan. Senyawa metabolit sekunder yang banyak ditemukan dalam temulawak adalah kurkuminoid yang tergolong dalam senyawa polifenol. Maserasi merupakan metode sederhana untuk mengekstrak senyawa metabolit sekunder dari tumbuhan. Selama prosesnya, jenis pelarut dan waktu maserasi menjadi faktor penting yang dapat memengaruhi hasil ekstraksi. Penelitian ini bertujuan untuk menganalisis pengaruh pelarut (akuades, etanol 50%, metanol 50%, dan aseton 50%) dan waktu ekstraksi (12, 24, 36, dan 48 jam) terhadap kadar total fenolik, total flavonoid, dan aktivitas antioksidan. Hasil pengujian menunjukkan bahwa etanol 50% memberikan hasil terbaik dengan kadar fenolik 36,29 mg GAE/g, flavonoid 66,96 mg QE/g, dan aktivitas antioksidan (metode CUPRAC) 117,13, Temulawak (Curcuma xanthorrhiza) contained secondary metabolite compounds such as phenolics and flavonoids with potential antioxidant activity. The most abundant secondary metabolite compound found in temulawak was curcuminoid. Maceration was a simple method for extracting secondary metabolite compounds from plants. During maceration, the type of solvent and the maceration time were crucial factors that affected the test results. This study aimed to analyze the effect of solvent (aquadest, 50% ethanol, 50% methanol, and 50% acetone) and extraction time (12, 24, 36, and 48 hours) on total phenolics, total flavonoids, and antioxidant activity. The results showed that 50% ethanol yielded the highest phenolic content (36,29 mg GAE/g), flavonoid content (66,96 mg QE/g DW), and antioxidant activity (CUPRAC method) of 117.06
Keyword: antioxidant, phenolic, flavonoid, solvent, time

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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