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: 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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