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.
Keyword: 

Judul: Inhibitor Tirosinase Ekstrak Metanol Berbagai Bagian Pohon Jabon dan Mangium
Abstrak: Jabon and mangium are currently planted in community forest. The wastes resulted from the utilization of forest products can reach 75%, including leaves barks, and woods. One of the ways to increase value of those wastes can be done by utilizing the extractive compounds contained in wood waste as tyrosinase inhibitor. Parts of tree which were extracted consist of leaves, barks, sapwood, and heartwood. The extraction method used in this research was soxhletation using methanol for 12 hours. The yield of extracts was 0.89-13.02%, with the lowest yield from sapwood of mangium and the highest was resulted by jabon’s leaves. Mangium bark extract had the highest activity as inhibitors of tyrosinase, with the value of IC50 was 129.81 ppm for the monophenolase reaction or three times higher than kojic acid (38.45 ppm) and 240.88 ppm for the diphenolase reaction or two times higher than kojic acid (102.11 ppm). The compounds contained within mangium bark extracts were expected to be inhibitor of tyrosinase, which was classified to flavonoids.
Keyword: tyrosinase inhibitor, monophenolase, mangium, jabon, Diphenolase

Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular