Judul: Potential of Active Compounds in Leaves, Seeds,  and Peel of Avocado Fruit (Persea americana Mill.) as In Silico Tyrosinase  Enzyme Inhibitors
Abstrak: Melanosit adalah komponen penting pigmentasi kulit melalui kemampuan mereka untuk menghasilkan melanin dibantu enzim tirosinase yang merupakan enzim inti dalam melanogenesis. Senyawa fenolik dan flavonoid yang tinggi padadaun, biji dan kulit buah alpukat memiliki potensi sebagai ligan (inhibitor) tyrosinase related protein-1. Penelitian ini bertujuan menentukan senyawa aktif dari daun, biji, dan kulit buah alpukat yang berperan dalam menghambat aktivitas enzim tirosinase pada manusia sehingga dapat menghambat pembentukan melanin. Penelitian dilakukan dengan metode penambatan molekuler menggunakan software YASARA Structure. Hasil penelitian menunjukan dari 68 senyawa aktif daun, biji, dan kulit buah alpukat terdapat 11 senyawa aktif yang memiliki afinitas pengikatan terhadap tyrosinase related protein-1 yaitu kuersetin, epikatekin, apigenin, 3- Hydroxytyrosol, scopoletin, asam absisat, asam sitrat, asam koumarat, asam kuinik, vanillin, dan asam kafeik. Senyawa aktif asam absisat merupakan ligan dengan potensi penghambatan terbaik dengan energi bebas ikatan (∆G) -2.645 kkal/mol yang berinteraksi dengan 17 residu asam amino. Hasil penelitian dapat digunakan sebagai acuan dalam studi in vitro dan in vivo terhadap enzim human tyrosinase. Kata kunci: Alpukat, Inhibitor, Melanin, Penambatan Molekuler, Tirosinase, Melanocytes are an important component of skin pigmentation through their ability to produce melanin assisted by the enzyme tyrosinase which is a core enzyme in melanogenesis. The high phenolic and flavonoid compounds in the leaves, seeds and skin of avocados have potential as ligands (inhibitors) of tyrosinase related protein-1. This study aims to determine the active compounds from the leaves, seeds, and skin of avocadosthat play a role in inhibiting the activity of the tyrosinase enzyme in humans so that it can inhibit the formation of melanin. The research was conducted by molecular anchoring method using YASARA Structure software. The results showed that of the 68 active compounds of avocado leaves, seeds, and skins, there were 11 active compounds that had binding affinity for tyrosinase related protein-1, namely quarcetin, epicatechin, apigenin, 3- Hydroxytyrosol, scopoletin, abscisic acid, citric acid, coumaric acid. , quinic acid, vanillin, and caffeic acid. The active compound abscisic acid is the ligand with the best inhibitory potential with a bond free energy (∆G) of -2,645 kcal/mol which interacts with 17 amino acid residues. The research results can be used as a reference in in vitro and in vivo studies of the human tyrosinase enzyme. Keywords: Avocado, Inhibitor, Melanin, Molecular Docking, Tyrosinase
Keyword: Avocado, Inhibitor, Melanin, Molecular Docking, Tyrosinase

Judul: Identification of Merbau Wood (Intsia palembanica) Active Compounds and Their Potential as In Silico Tyrosinase Enzyme Inhibitors
Abstrak: Tirosinase merupakan enzim pembatas laju yang terkait dengan sintesis melanin dalam melanosit. Peningkatan produksi melanin (melanogenesis) di melanosit menyebabkan terjadinya hiperpigmentasi atau penggelapan kulit. Senyawa aktif kayu merbau dapat digunakan sebagai inhibitor tirosinase. Penelitian ini bertujuan mengidentifikasi senyawa aktif kayu merbau dengan LC-MS serta menguji potensi senyawa aktif tersebut sebagai inhibitor tirosinase melalui parameter Energi Bebas Ikatan (∆G), Konstanta Disosiasi (Kd), dan jenis interaksi yang terbentuk antara ligan dan reseptor. Metode yang digunakan dalam penelitian ini adalah ekstraksi, LC-MS, dan penambatan molekuler menggunakan perangkat lunak YASARA Structure dengan reseptor 5M8M yang berasal dari homo sapiens. Hasil penelitian menunjukkan bahwa terdapat 25 senyawa aktif ekstrak etanol kayu merbau hasil LC-MS. Sebanyak 1 dari 25 senyawa yang berpotensi sebagai inhibitor tirosinase yaitu senyawa artemidiol. Senyawa artemidiol menunjukkan aktivitas inhibitor tirosinase terbaik dengan nilai ∆G sebesar -7.231 kkal/mol dan Kd 5.007 µM. Senyawa artemidiol memiliki 5 ikatan hidrogen. Simpulan dari penelitian adalah ligan uji artemidiol sangat berpotensi sebagai inhibitor tirosinase daripada ligan alami asam kojat., Tyrosinase is a rate limiting enzyme associated with melanin synthesis in melanocytes. Increased melanin production (melanogenesis) in melanocytes causes hyperpigmentation or darkening of the skin. The active compound of merbau wood can be used as a tyrosinase inhibitor. This study aimed to identify the active compound merbau wood with LC-MS and to test the potential of the active compound as a tyrosinase inhibitor through the parameters of bond free energy (∆G), dissociation constant (Kd), and the type of interaction formed between the ligand and the receptor. The methods used in this study were extraction, LC-MS, and molecular anchoring using YASARA Structure software with 5M8M receptors derived from homo sapiens. The results showed that there were 25 active compounds in the ethanol extract of merbau wood from LC-MS. As many as 1 of 25 compounds that had the potential as tyrosinase inhibitors were artemidiol compounds. Artemidiol compounds showed the best tyrosinase inhibitor activity with G values of -7.231 kcal/mol and Kd of 5.007 µM. Artemidiol compounds had 5 hydrogen bonds. The conclusion of the research was that the artemidiol test ligand had the potential as a tyrosinase inhibitor rather than the natural ligand of kojic acid.
Keyword: Hyperpigmentation, Melanogenesis, Merbau Wood, Molecular Docking, Tyrosinase

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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