Judul: Antioxidant Activity of Saffron (Crocus sativus) Extracts by Thiobarbituric Acid Method
Abstrak: Saffron berasal dari putik bunga saffron (Crocus sativus) dikenal sebagai rempah termahal di dunia memiliki manfaat dalam berbagai bidang seperti kesehatan, makanan, dan kecantikan. Saffron memiliki kandungan senyawa yang dapat berperan sebagai antioksidan sehingga mengurangi risiko munculnya berbagai penyakit akibat radikal bebas yang memicu stress oksidatif. Penelitian bertujuan menguji aktivitas antioksidan ekstrak etil asetat, etanol dan air saffron dengan metode asam tiobarbiturat. Ekstraksi pada pelarut etil asetat dan etanol dilakukan menggunakan metode ekstraksi bertingkat dengan perbandingan 1:10 (b/v) sedangkan ekstraksi pada pelarut aquades dilakukan secara terpisah dengan perlakuan penyeduhan. Hasil pengujian menunjukkan ekstrak etil asetat memiliki nilai IC50 sebesar 40.78 μg/mL, ekstrak etanol 242.80 μg/mL, dan ekstrak air 70.81μg/mL. Ekstrak etil asetat saffron termasuk dalam golongan antioksidan sangat kuat berdasarkan nilai IC50., Saffron comes from the pistils of the flower Saffron (Crocus sativus) is known as the most expensive spice in the world and has benefits in various fields such as health, food, and beauty. Saffron contains compounds that can act as antioxidants and reduce the risk of various diseases caused by free radicals. The research aim is to determine the antioxidant activity of ethyl acetate extract, ethanol extract, and water extract of saffron in vitro using the thiobarbituric acid method. The result showed ethyl acetate extract had IC50 value 40.78 μg/mL, ethanol extract 242.80 μg/mL and aqueous extract 70.81 μg/mL. The Ethyl acetate extract of saffron belongs to the class of very strong antioxidants based on the IC50 value.
Keyword: antioksidan, asam tiobarbiturat, saffron, radikal bebas, antioxidant, free radical, saffron, thiobarbituric acid

Judul: Literature Review Effect of Drying and Extraction Methods on Sargassum sp Antioxidant Activity
Abstrak: Antioksidan merupakan senyawa aktif yang berperan dalam mencegah efek negatif radikal bebas. Tujuan penelitian ini adalah mengidentifikasi, menganalisis dan membandingkan sumber pustaka mengenai pengaruh metode pengeringan dan ekstraksi dengan beberapa pelarut terhadap aktivitas antioksidan Sargassum sp. Rataan total fenol metode pengeringan sebesar 1.335±0.615 mg GAE/g berat kering (oven) dan 24.020±4.029 mg GAE/g berat kering (kering angin) dengan rataan tertinggi pada pengeringan kering angin. Rataan total fenol metode ekstraksi sebesar 4.132±2.565 mg GAE/g berat kering (semi-polar) dan 17.135±6.032 mg GAE/g berat kering (polar) dengan rataan tertinggi pada penggunaan pelarut polar. Rataan aktivitas antioksidan metode pengeringan sebesar 63.12±31.09 ppm (kering angin) dan 1840.85±1059.46 ppm (oven) dengan rataan aktivitas antioksidan tertinggi pada pengeringan kering angin. Rataan aktivitas antioksidan metode ekstraksi sebesar 45.55±9.11 ppm (polar) dan 98.14±6.03 ppm (semi-polar) dengan rataan aktivitas antioksidan tertinggi pada penggunaan pelarut polar. Oleh karena itu, metode pengeringan kering angin dan ekstraksi dengan pelarut polar merupakan metode terbaik dalam menghasilkan antioksidan yang kuat., Antioxidants are active compounds that play a role in preventing the negative effects of free radicals. The purpose of this study was to identify, analyze and compare literature sources on the effect of drying and extraction methods with some solvents on the antioxidant activity of Sargassum sp. The average of total phenol drying method was 1.333±0.615 mg GAE/g dry weight (oven) and 24.020±4.029 mg GAE/g dry weight (shade dried) with the highest average in shade dried. The average of total phenol extraction method was 4.132±2.565 mg GAE/g dry weight (semi-polar) and 17.135±6.032 mg GAE/g dry weight (polar) with the highest average in extraction with polar solvent. Antioxidant activity of drying methods was 63.12±31.09 ppm (shade dried) and 1840.85±1059.46 ppm (oven) with the highest average in shade dried. The average of antioxidant activity of extraction methods was 45.55±9.11 ppm (polar) and 98.14±6.03 ppm (semi-polar) with the highest average in extraction with polar solvent. Therefore, drying with shade dried and extraction with polar solvents was the best method of producing strong antioxidants.
Keyword: antioxidant, drying, extraction, Sargassum sp.

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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