Judul: Penambatan Molekul Senyawa Aktif Kulit Lemon terhadap Listeria monocytogenes dan Potensinya sebagai Fruitsanitizer
Abstrak: Permintaan terhadap buah-buahan tidak diikuti dengan tingkat keamanannya. Buah-buahan yang beredar di pasaran berisiko tinggi terkontaminasi bakteri, fungi, dan residu pestisida. Oleh karena itu, dibutuhkan suatu produk yang dapat mengurangi kontaminasi mikroorganisme dan pestisida pada buah secara praktis, efektif, dan efisien tanpa perlu dibilas dengan air. Kulit lemon memiliki kandungan metabolit sekunder yang berpotensi sebagai bahan dasar fruitsanitizer. Penelitian ini bertujuan menentukan metabolit sekunder yang berperan pada ekstrak kulit lemon dalam menginhibisi patogen penyebab listeriosis (Listeria monocytogenes) in silico dan efektivitasnya sebagai bahan dasar fruitsanitizer untuk mengurangi kontaminasi mikroorganisme dan residu pestisida in vitro. Metode yang digunakan adalah penambatan molekul dengan Vina, uji antimikroba, uji tegangan permukaan, dan uji BSLT. Hasil penambatan molekul menunjukkan kuersetin pada kulit lemon memiliki potensi terbaik sebagai inhibitor enzim piruvat karboksilase Listeria monocytogenes dengan energi afinitas sebesar -5.1 kkal/mol dan kemampuan kulit lemon sebagai antimikroba serta melarutkan residu pestisida sama dengan handsanitizer dengan IC50 kategori toksik (131.67 ppm)., The demand for fruits is not followed by their safety. Fruits on the market have a high risk of contamination, such as bacteria, fungi, and pesticide residues. Therefore, we need a product that can reduce the contamination of microorganisms and pesticides on fruit in a practical, effective, and efficient without the need to be rinsed with water. Lemon peel contains secondary metabolites that have the potential as a primary ingredient for fruitsanitizer. This study aims to determine the secondary metabolites that play a role in lemon peel extract in inhibiting the pathogen that causes listeriosis (Listeria monocytogenes) in silico and its effectiveness as a primary ingredient for fruitsanitizer to reduce contamination of microorganisms and pesticide residues in vitro. The method used was molecular docking with Vina, antimicrobial test, surface tension test, and BSLT test. The result of molecular docking showed that quercetin in the lemon peel had the best potential inhibit Listeria monocytogenes pyruvate carboxylase enzyme with affinity energy value -5.1 kcal/mol. The ability of lemon peel as an antimicrobial and dissolve pesticide residues is the same as a hand-sanitizer with IC50 toxic category (131.67 ppm).
Keyword: Fruitsanitizer, Kuersetin, Kulit Lemon, Listeria monocytogenes, Piruvat Karboksilase, Fruitsanitizer, Lemon peel, Listeria monocytogenes, Pyruvate carboxylase, Quercetin

Judul: Potensi Kulit Buah Langsat (Lansium domesticum) sebagai Antibakteri
Abstrak: The fruit peels of langsat (Lansium domesticum) have antibacterial activities. However, the active compounds responsible for the activities have not been studied. Therefore, this research was aimed to determine the metabolite compounds with antibacterial activity in the fruit peel of langsat. Some samples was macerated using ethanol 70% and further fractionated using column chromatography with gradient elution from non-polar to polar solvent. Antibacterial activity was tested to Staphylococcus aureus using dilution method. Antibacterial test results showed that the most active extracts was ethanol 70% extract with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 1.00 mg/mL. Fractionation using hexane:ethyl acetate gave 12 fractions and 9 fractions for ethyl acetate:methanol. The most active fraction was F29 with MIC and MBC of 0.5 mg/mL and 2.00 mg/mL, respectively. Based on identification using Fourier transform infrared spectrophotometers, the predicted active compound was flavonoids.
Keyword: fruit peels langsat, fraction, flavonoid, antibacterial

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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