Judul: In Silico Study of Mahogany Bark Active Compounds as  Inhibitor of RNA-dependent RNA polymerase and Endoribonuclease SARS-CoV-2 EPI_ISL_46737
Abstrak: RNA-dependent RNA polymerase dan endoribonuclease merupakan protein yang berperan dalam replikasi dan transkripsi SARS-CoV-2 penyebab Covid-19. Kulit kayu mahoni mengandung senyawa golongan polifenol yang memiliki aktivitas antivirus, antioksidan, dan antimikroba. Hingga saat ini belum ada riset senyawa aktif kulit kayu mahoni sebagai inhibitor protein RNA-dependent RNA polymerase dan endoribonuclease. Penelitian ini bertujuan untuk mempelajari interaksi senyawa aktif kulit kayu mahoni terhadap protein RNA-dependent RNA polymerase dan endoribonuclease SARS-CoV-2. Penelitian dilakukan secara in silico dengan teknik penambatan molekuler menggunakan program YASARA. Hasil penelitian dianalisis menggunakan parameter energi bebas Gibbs, konstanta disosiasi, dan interaksi residu. Swietemakrofilanin berpotensi dalam menghambat RNA-dependent RNA polymerase dengan ΔG -4,053 kkal/mol, Kd 1.069 µM, tiga ikatan hidrogen, enam interaksi hidrofobik. Katekin berpotensi dalam menghambat endoribonuclease dengan ΔG -1,700 kkal/mol, Kd 56.739 µM, satu interaksi hidrofobik. Berdasarkan hasil penambatan, kulit kayu mahoni memiliki potensi sebagai inhibitor RNA dependent RNA polymerase dan endoribonuclease SARS CoV-2., RNA-dependent RNA polymerase and endoribonuclease are proteins that play a role in the replication and transcription of SARS-CoV-2 that causes Covid 19. Mahogany bark contains polyphenolic compounds that have antiviral, antioxidant, and antimicrobial activity. Until now, there has been no research on the active compound of mahogany bark as an inhibitor of RNA-dependent RNA polymerase and endoribonuclease. This study aimed to study the interaction of active compounds from mahogany bark on RNA-dependent RNA polymerase and endoribonuclease SARS-CoV-2. The research was conducted in silico with molecular docking using YASARA program. The results were analyzed using Gibbs free energy, dissociation constants, and residual interactions parameters. Swietemacrophylllanin has the potential to inhibit RNA-dependent RNA polymerase with ΔG -4,053 kcal/mol, Kd 1,069 µM, three hydrogen bonds, six hydrophobic interactions. Catechin has the potential to inhibit endoribonuclease with ΔG -1,700 kcal/mol, Kd 56,739 µM, one hydrophobic interaction. Based on the results, mahogany bark has the potential as an inhibitor of RNA-dependent RNA polymerase and endoribonuclease SARS-CoV-2.
Keyword: Covid-19, Endoribonuklease, Katekin, RdRp, Swietemakrofilanin

Judul: In Silico Potency of Active Compound in Mahony Bark as RBD Spike and Nucleocapsid SARS-CoV-2 Inhibitor from Indonesian Patient
Abstrak: RBD spike dan nukleokapsid merupakan bagian protein struktural SARS-CoV-2 yang masing-masing berperan utama mengikat reseptor spesifik dalam sel inang (ACE2) serta mengikat genom RNA virus dan mengemasnya ke dalam struktur ribonukleoprotein. Senyawa aktif kulit kayu mahoni termasuk golongan flavanol yang memiliki aktivitas antioksidan dan antimikroba. Penelitian ini bertujuan menganalisis interaksi molekuler senyawa aktif kulit kayu mahoni terhadap RBD spike dan nukleokapsid dari SARS-CoV-2 EPI_ISL_467376 asal pasien Indonesia. Metode yang digunakan dalam penelitian ini adalah penambatan molekuler menggunakan perangkat lunak YASARA Structure. Hasil penelitian menunjukkan bahwa katekin berpotensi terbaik sebagai inhibitor interaksi RBD spike dengan ACE2 (energi ikatan -3,911 kkal/mol dan Kd 0,135×104 μM). Katekin juga berpotensi terbaik sebagai inhibitor interaksi nukleokapsid dengan genom RNA virus dalam pembentukan kompleks ribonukleopreotein (energi ikatan -2,027 kkal/mol dan Kd 3,267×104 μM)., RBD spike and nucleocapsid are parts of SARS-CoV-2 structural proteins that each play a major role in binding to a specific receptor in the host cell (ACE2) and binding to the viral RNA genome and packaging it into a ribonucleoprotein structure. The active compounds of mahogany bark belongs to the flavanol group which have antioxidant and antimicrobial activity. This study aims to analyze the molecular interactions of active compounds from mahogany bark on the RBD spike and nucleocapsid of SARS-CoV-2 EPI_ISL_467376 from an Indonesia patient. The method used in this research is molecular docking using YASARA Structure software. The results show that catechin has the best potential as inhibitor of the interaction of the RBD spike with ACE2 (binding energy of -3.911 kcal/mol and Kd 0.135×104 μM). Catechin also has the best potential as inhibitor of nucleocapsid interaction with viral RNA genomes in the formation of ribonucleoprotein complexes (binding energy of -2.027 kcal/mol and Kd 3.267×104 μM).
Keyword: kulit kayu mahoni, katekin, nukleokapsid, RBD spike, SARS-CoV-2

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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