Judul: Potency of Alamanda in Bogor Area as Tyrosinase Inhibitor
Abstrak: Alamanda is one of ornament plant widely available in Indonesia. Stem of Allamanda cathartica has been known as a tyrosinase inhibitor. The purpose of this research were to discover the species of alamanda in some areas in Bogor which have the best tyrosinase inhibitory activity and to fractionate and identify the active component in alamanda’s extract for its activity as tyrosinase inhibitor. Alamanda samples were taken from Cipanas, Cibirus, Cisarua, and Cikabayan. The samples consisted of two species: A. schottii and A. cathartica. A. schottii was collected from Cipanas, Cisarua, and Cikabayan 1 while A. cathartica was collected from Cikabayan 2 and Cibirus. All samples were extracted with two different solvents, water and methanol. The water extract of A. schottii leaves from Cipanas showed the best activity as tyrosinase inhibitor (IC50 monophenolase: 80.75 μg/mL and diphenolase: 112.04 μg/mL). The active component was identified using phytochemical test, spectrophotometer UV-Visible, and Fourier transform infrared (FTIR) techniques. The results showed that the active compound as tyrosinase inhibitor could be in the flavonoids group, specifically flavonol.
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Judul: Aktivitas Gabungan Ekstrak Bakau (Rhizophora apiculata), Alamanda (Allamanda schottii), dan Binahong (Anredera cordifolia) terhadap Enzim Tirosinase
Abstrak: The aim of this study was to determine the most active composition of mangrove, alamanda, and binahong extract as tyrosinase inhibitor and antioxidant. Stem of mangrove was extracted with methanol-water and fractionated to obtain flavonoid extract, leaves of alamanda were extracted with water, and leaves of binahong were extracted with ethanol. Each extracts were combined based on the extract weight using simplex centroid design, then tested its tyrosinase inhibitor and antioxidant activities (DPPH). Single extract of mangrove stem (IC50 monophenolase: 202 μg/mL; IC50 diphenolase: 419 μg/mL) had the best activity as tyrosinase inhibitor. The combined extract of mangrove:alamanda:binahong (2/3:1/6:1/6) had good inhibition activity on monophenolase stage (IC50 147 μg/mL). The extract and combination also showed good antioxidant activity (IC50 23 μg/mL and 50 μg/mL, respectively). Thin layer chromatography fingerprint pattern of single extract of mangrove eluted with diethyl ether:ethyl acetate (1:1) showed 4 spots, and the combined extract of mangrove:alamanda:binahong (2/3:1/6:1/6) showed the same spot with an Rf of 0.11.
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Judul: Persamaan Geodesik Black Hole dengan Metrik Kerr 4+1 Dimensi dalam Koordinat Waktu Kosmik
Abstrak: Persamaan geodesik black hole dengan metrik Kerr 4+1 dimensi dalam koordinat waktu kosmik merupakan interpretasi lain dari persamaan geodesik black hole dengan metrik Kerr 4+1 dimensi, dimana acuan waktu yang digunakan diubah dari koordinat waktu wajar (proper time) ke dalam koordinat waktu kosmik (cosmic time). Waktu kosmik merupakan koordinat waktu yang dimana pengamat bergerak mengikuti ekspansi dari alam semesta. Penelitian ini merekonstruksi persamaan geodesik black hole dengan metrik Kerr 4+1 dimensi yang telah ditemukan pada penelitian sebelumnya menjadi persamaan geodesik yang memiliki fungsi terhadap dimensi waktu (t). Hasil akhir dari transformasi persamaan dapat digunakan sebagai bahan studi pustaka untuk penelitian lebih lanjut mengenai persamaan geodesik black hole dalam koordinat waktu kosmik.
Keyword: Dimensi ekstra, Metrik Kerr, Persamaan geodesik, Waktu kosmik