Judul: Antioxidant Activity of Sargassum sp. Extracts with Different Drying Methods
Abstrak: Rumput laut Sargassum sp. merupakan salah satu jenis rumput laut yang kaya akan senyawa bioaktif dengan aktivitas antioksidan. Penggunaan metode pengeringan yang tepat sangat penting untuk mempertahankan aktivitas senyawa antioksidan. Penelitian ini bertujuan untuk mengevaluasi aktivitas antioksidan dan bioautografi ekstrak Sargassum sp. dengan metode pengeringan yang berbeda. Pengeringan dilakukan menggunakan oven, sinar matahari langsung dan pengeringan kering angin. Tahapan penelitian meliputi ekstraksi, pengujian aktivitas antioksidan dengan metode DPPH 2,2- diphenyl-1-picrylhydrazyl, dan analisis bioautografi. Hasil penelitian menunjukkan bahwa metode pengeringan memengaruhi kadar antioksidan dalam ekstrak Sargassum sp. Ketiga pengeringan penjemuran langsung, pengeringan angin-angin serta oven menunjukkan adanya aktivitas antioksidan dengan nilai Rf masing-masing 0,19; 0,54 dan 0,77. Senyawa saponin, steroid dan polifenol terdeteksi pada ketiga metode pengeringan. Hasil aktivitas antioksidan yang didapat secara berurutan dengan nilai IC50 diatas 1000 ppm, 467 ppm dan 951 ppm. Penelitian ini menunjukkan bahwa metode pengeringan dengan oven lebih efektif dalam mempertahankan aktivitas antioksidan pada ekstrak Sargassum sp., Sargassum sp. is a type of seaweed rich in bioactive compounds with antioxidant activity. The appropriate drying method is crucial to retain the activity of these compounds. This study aimed to evaluate the antioxidant activity and bioautography of Sargassum sp. extracts with different drying methods. Drying was performed using an oven, direct sunlight, and ambient drying. The methods used included extraction, antioxidant activity testing using the DPPH method, and bioautography analysis. The results showed that the drying method affected the antioxidant content in Sargassum sp. extracts. The three drying methods—direct sunlight, air drying, and oven drying—showed antioxidant activity with Rf values of 0.19, 0.54, and 0.77, respectively. Saponins, steroids, and polyphenols were detected in all three drying methods. The antioxidant activity results, measured by IC50 values, were above 1000 ppm, 467 ppm, and 951 ppm, respectively. This study concludes that oven drying is more effective in maintaining antioxidant activity in Sargassum sp. extracts.
Keyword: Bioautography, brown alga, extraction, IC50, thin layer chromatography

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: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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