Judul: Total Tannin Content and Antioxidant Activity of Red Betel Leaf Extracts (Piper crocatum) From Bogor, Bandung, Solo and Malang Using FRAP Method
Abstrak: Sirih merah merupakan salah satu tanaman yang telah banyak diteliti sebagai sumber antioksidan. Tujuan penelitian ini untuk menentukan kadar total tanin dan aktivitas antioksidan ekstrak daun sirih merah dari 4 daerah di Indonesia yaitu Bogor, Bandung, solo dan Malang. Ekstraksi dilakukan menggunakan metode maserasi dengan etanol 70% sebagai pelarut. Rendemen ekstrak etanol didapatkan rentang antara 8,27 hingga 14,19 dengan rendemen terbaik didapatkan oleh sirih merah Malang. Pengukuran kadar total tanin menggunakan metode titrasi dan pengukuran aktivitas antioksidan menggunakan metode FRAP. Hasil penelitian menunjukkan ekstrak etanol daun sirih merah memiliki rentang kadar total tanin antara 20,33 hingga 64,91 mg/g tanin dan rentang aktivitas antioksidan antara 2,54 hingga 3,45 mg TE/g. Hasi kadar total tanin dan aktivitas antioksidan tertinggi didapatkan pada daun sirih merah Bandung dengan nilai 64,90 mg/g tanin dan 3,45 mg TE/g ekstrak. Korelasi pearson tidak dapat dilakukan karena sebaran data kadar total tanin tidak normal., Red betel (Piper crocatum) is one of the plants that has been extensively researched as a source of antioxidants. The purpose of this study was to determine the total tannin content and antioxidant activity of red betel leaf extract from 4 regions in Indonesia, namely Bogor, Bandung, Solo, and Malang. Extraction was carried out using the maceration method with 70% ethanol as the solvent. The yield of ethanol extract ranged between 8.27 to 14.19, with the best yield obtained from Malang red betel. The measurement of total tannin content was performed using the titration method, and the measurement of antioxidant activity was conducted using the FRAP method. The results showed that the ethanol extract of red betel leaves had a total tannin content range between 20.33 to 64.91 mg/g tannin and an antioxidant activity range between 2.54 to 3.45 mg TE/g. The highest total tannin content and antioxidant activity were obtained from red betel leaves from Bandung, with values of 64.90 mg/g tannin and 3.45 mg TE/g extract, respectively. Pearson correlation could not be performed because the distribution of total tannin content data was not normal.
Keyword: Antioxidant, FRAP, Red Betel, Tannin

Judul: Kadar Total Fenolik, Flavonoid, dan Aktivitas Inhibisi Tirosinase dari Fraksi Ekstrak Sirih Merah (Piper crocatum Ruiz  & Pav) Asal Semarang
Abstrak: Sirih merah (Piper crocatum Ruiz & Pav) merupakan tanaman obat potensial yang dapat menyembuhkan berbagai jenis penyakit seperti diabetes mellitus, asam urat, hipertensi, dan kanker. Selain itu, daun sirih merah diketahui dapat mencegah dan menyembuhkan jerawat, dan mencerahkan kulit wajah kusam. Senyawa aktif pada sirih merah seperti fenolik dan flavonoid dapat berperan dalam menangani hiperpigmentasi dengan menghambat enzim tirosinase. Penelitian ini bertujuan menganalisis kadar total fenolik, flavonoid, dan aktivitas inhibisi tirosinase dari hasil fraksinasi ekstrak etanol sirih merah asal Semarang. Ekstraksi dilakukan dengan maserasi menggunakan etanol 70%, dan selanjutnya difraksinasi dengan 3 pelarut, yaitu n-heksana, etil asetat, dan air. Kadar total fenolik dan flavonoid tertinggi terdapat pada fraksi etil asetat yaitu sebesar 80.294 mg GAE/g dan 61.537 mg QE/g. Nilai penghambatan terhadap tirosinase terbesar juga terdapat pada fraksi etil asetat (65.86%). Aktivitas penghambatan tirosinase menunjukkan bahwa fraksi etil asetat memiliki nilai IC50 3470.53 ppm. Fraksi etil asetat daun sirih merah asal Semarang memiliki kemampuan sebagai inhibitor tirosinase lebih baik dibandingkan dengan fraksi n-heksana, fraksi air, dan ekstrak etanol 70%., Red betel (Piper crocatum Ruiz & Pav) is a potential medicinal plant that can cure various types of diseases such as diabetes mellitus, gout, hypertension, and cancer. Furthermore, red betel leaves are known to prevent and cure acne, and able to brighten facial skin. Active compounds in red betel such as phenolics and flavonoids are able to treat hyperpigmentation by inhibiting the tyrosinase. This research aimed to analyze total phenolics contents, flavonoids contents, and tyrosinase inhibitory activity from the fractionated ethanol extract of red betel from Semarang. The extraction was performed using maceration with 70% ethanol, and then fractionated with 3 solvents, n-hexane, ethyl acetate, and water. The highest total phenolics and flavonoids contents were found in the ethyl acetate fraction with values of 80.294 mg GAE/g and 61.537 mg QE/g. The highest inhibition value of tyrosinase was also found in the ethyl acetate fraction (65.86%). Tyrosinase inhibition activity showed that the ethyl acetate fraction has IC50 value of 3470.53 ppm. Therefore, the ethyl acetate fraction of red betel leaves from Semarang is proven to be a better tyrosinase inhibitor compared to the n-hexane fraction, water fraction, and 70% ethanol extract.
Keyword: phenolic, flavonoid, tyrosinase enzyme, red betel

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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