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: Potensi Ekstrak Rhizophora sp. sebagai Inhibitor Tirosinase
Abstrak: Rhizophora sp. is one of plant type that has benefit as medicinal plants, for example, as whitening agent. The purpose of this study is to discover the parts and species of Rhizophora sp. which have best tyrosinase inhibitory activity. Leaves, stems, and roots of R. mucronata and R. stylosa were extracted with methanol and were tested their activities in order to obtain the best tyrosinase inhibitory activity. Based on the results, extracts of leaves, stems, and roots of R. mucronata from Tritih, Cilacap; Gebang, Cirebon; Eretan Kulon, Indramayu; Ujung Negoro Beach, Batang; Sigundu Beach, Batang; and Kapuk Beach, Jakarta were not potencial as tyrosinase inhibitor. Tyrosinase inhibitor activity from roots of R. mucronata from Samboja, East Kalimantan was higher than from its leaves and stems, especially for monophenolase with IC50 15.34 μg/ml. In perponderonce with, tyrosinase inhibitor activity from stems of R. stylosa from Samboja, East Kalimantan was also higher compared with stems of R. mucronata with IC50 38.02 μg/ml.
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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