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: Antioxidant Activity and Metabolite Profile of Brown Marine Algae Sargassum sp. from a Different Location
Abstrak: Sargassum sp. memiliki potensi untuk dikembangkan karena mengandung beragam senyawa bioaktif. Lokasi dan kondisi pertumbuhan yang berbeda dapat berdampak pada komposisi senyawa bioaktif sehingga perlu dilakukan penelitian untuk mendapatkan informasi kelimpahan metabolit yang terkandung. Penelitian ini bertujuan mengevaluasi dan menentukan aktivitas antioksidan, senyawa fitokimia, dan profil metabolit Sargassum sp. yang berasal dari perairan Kepulauan Seribu, Ujung Genteng, dan Buton. Sampel Sargassum sp. diekstrak menggunakan metode maserasi dengan pelarut metanol untuk mendapatkan ekstrak kasar. Ekstrak kasar difraksinasi dengan kromatografi lapis tipis (KLT) lalu dilakukan evaluasi aktivitas antioksidan dan penentuan senyawa fitokimia secara kualitatif. Evaluasi aktivitas antioksidan secara kuantitatif dilakukan menggunakan reagen 1,1-difenil2-pikrilhidrazil (DPPH) dengan instrumen spektrofotometer UV-Vis. Penentuan profil metabolit menggunakan instrumen UPLC-MS. Hasil penelitian menunjukkan aktivitas antioksidan Sargassum sp. dari ketiga lokasi tergolong kuat. Nilai IC50 Sargassum sp. dari Kepulauan Seribu, Ujung Genteng, dan Buton secara berturutturut 65,277 ppm, 67,044 ppm, dan 62,412 ppm. Senyawa fitokimia yang teridentifikasi yaitu steroid, saponin, dan polifenol. Hasil analisis PCA menunjukkan tingkat kemiripan antar sampel tidak signifikan. Ditemukan delapan senyawa penciri, empat senyawa penciri yang teridentifikasi tergolong kedalam senyawa amida, amina ester (surfaktan), lipida betain, dan naphthyridine. Empat senyawa penciri lain tidak teridentifikasi., Sargassum sp. has the potential to be developed because it contains a variety of bioactive compounds. Different locations and growth conditions can have an impact on the composition of bioactive compounds, so it is necessary to carry out research to obtain information on the abundance of metabolites contained. This study aims to evaluate and determine the antioxidant activity, phytochemical compounds, and metabolite profile of Sargassum sp. originating from the waters of the Seribu Islands, Ujung Genteng, and Buton. Samples of Sargassum sp. were extracted using the maceration method with methanol as the solvent to obtain crude extracts. The crude extracts were fractionated using thin-layer chromatography (TLC), followed by evaluating antioxidant activity and determining phytochemical compounds qualitatively. Quantitative evaluation of antioxidant activity was performed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) reagent with a UV-Vis spectrophotometer instrument. The metabolite profile was determined using UPLC-MS instrumentation. The results showed the antioxidant activity of Sargassum sp. quite strong. IC50 value of Sargassum sp. from the Seribu Islands, Ujung Genteng, and Buton respectively 65.277 ppm, 67.044 ppm and 62.412 ppm. The identified phytochemical compounds are steroids, saponins, and polyphenols. PCA analysis results show that the level of similarity between samples is not significant. There are eight marker compounds, four identified marker compounds are classified as amides, amine esters (surfactants), betaine lipids, and naphthyridine. The other four marker compounds were not identified.
Keyword: antioxidants, metabolomics, phytochemicals, Sargassum sp., UPLC-MS

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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