Judul: Potensi Antioksidan, Inhibitor Tirosinase, dan Nilai Toksisitas dari Beberapa Spesies Tanaman Mangrove di Indonesia
Abstrak: Indonesia is a country rich in biodiversity. Mangrove is a plant that quite a lot in Indonesia. This research was conducted to determine potency of antioxidant, tyrosine inhibitors, and toxicity from some types of mangrove plants. The result showed that the yield of R. stylosa bark extract was 18.07% and it was the highest yield extract. S. caseolaris fruit extract had the lowest LC50 of toxicity (126.73 μg/mL). S. caseolaris bark extract had antioxidant best value with IC50 of 3.03 μg/mL. This extract also had the best potency of tyrosinase inhibitors with IC50 value of 117.67 mg/mL for monophenols and 364.99 mg/mL for diphenols. Active compounds detected in S. caseolaris extract were tannins, saponin, flavonoid, and phenol hydroquinone. S. caseolaris bark extract was the best extract due to the best ability of antioxidant activity and tyrosinase inhibitory activity.
Keyword: Bogor Agricultural University (IPB), toxicity, mangrove, inhibitors tyrosinase, best extract, antioxidant

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