Judul: Antioxidant Activity and Total Flavonoids Content of Water and Ethanol Extract of Surian Leaves (Toona sinensis) on Various Tree Ages
Abstrak: Ekstrak daun tanaman surian diketahui memiliki kandungan senyawa flavonoid yang berfungsi sebagai antioksidan. Penelitian ini bertujuan menguji aktivitas antioksidan dan menghitung kadar total flavonod dari ekstrak air dan etanol daun surian pada berbagai umur pohon surian. Penelitian ini menggunakan pelarut air, etanol 30%, 70% dan 96% pada umur tanaman 16, 27 dan 34 tahun. Kadar total flavonoid diukur menggunakan metode Alumunium Klorida (AlCl3) dan aktivitas antioksidan menggunakan metode FRAP. Hasil penelitian menunjukan ekstrak etanol 96% daun surian menghasilkan kadar total flavonoid dan aktivitas antioksidan FRAP tertinggi pada umur tanaman 34 tahun dan ekstrak air daun surian menghasilkan kadar total flavonoid dan aktivitas antioksidan FRAP terendah pada umur tanaman 16 tahun. Kadar total flavonoid tertinggi sebesar 84.4559 mg QE/g DW dan kadar total flavonoid terendah sebesar 5.1069 mg QE/g DW. Aktivitas antioksidan FRAP tertinggi sebesar 330.061 μmol TE/g DW dan aktivitas antioksidan FRAP terendah sebesar 837.939 μmol TE/g DW. Simpulan dari penelitian adalah semakin tinggi kadar total flavonoid pada ekstrak daun surian maka semakin berpotensi sebagai sumber antioksidan alami., Surian leaves extract is known to contain flavonoid compounds that function as antioxidants. This study aimed to examine the antioxidant activity and calculate the levels of flavonoid from the aqueous and ethanol extracts of surian leaves from various ages of surian trees. This study used water, 30%, 70%, and 96% ethanol as a solvent for the surian plants ages 16, 27, and 34 years. Total flavonoid levels are measured using the Aluminum Chloride (AlCl3) method and antioxidant activity using the FRAP method. The results showed that the 96% ethanol extract of surian leaves produced the highest levels of total flavonoids and FRAP antioxidant activity at the age of 34 years and the aqueous extract of surian leaves produced the lowest levels of total flavonoids and antioxidant activity of FRAP at the age of 16 years. The highest total flavonoid content is 84.4559 mg QE/g DW and the lowest total flavonoid content is 5.1069 mg QE/g DW. The highest FRAP antioxidant activity is 330.061 μmol TE/g DW and the lowest FRAP antioxidant activity is 837.939 μmol TE/g DW. The conclusion from the research is that the higher the total flavonoid content in surian leaves extract, the more potential it is as a source of natural antioxidants.
Keyword: antioxidant, FRAP, surian leaves, flavonoids

Judul: Total Phenolic and Antioxidant Activity of Surian (Toona Sinensis) Leaves on Various Tree Age and Solvent Concentration
Abstrak: Ekstrak daun surian (Toona sinensis) memiliki kandungan senyawa fenolik yang dapat berpotensi sebagai antioksidan alami. Pengoptimalan umur panen tanaman serta konsentrasi pelarut (etanol) diperlukan untuk mendapatkan aktivitas antioksidan daun surian terbaik. Penelitian ini bertujuan menguji pengaruh dari variasi umur pohon dan konsentrasi pelarut etanol terhadap kadar total fenolik dan aktivitas antioksidan yang terkandung dalam sampel daun surian asal Sumedang menggunakan uji analisis in vitro. Kadar total fenolik diukur dengan menggunakan metode Folin-Ciocalteu, sedangkan aktivitas antioksidan diukur menggunakan metode 2,2-difenil-1-pikrilhidrazil (DPPH). Ekstrak daun surian umur 34 tahun menggunakan pelarut etanol 96% memiliki kadar total fenolik tertinggi yaitu sebesar 392.28 mg GAE/g bobot kering dan menghasilkan kapasitas antioksidan tertinggi yaitu sebesar 1130.26 μm TE/g bobot kering dengan nilai IC50 terkecil dibandingkan dengan sampel lainnya yaitu sebesar 4.19 μg/mL sehingga dapat dikatakan bahwa ekstrak daun surian 34 tahun menggunakan pelarut etanol 96% memiliki aktivitas antioksidan terbaik. Umur pohon dan konsentrasi pelarut etanol terbukti dapat mempengaruhi hasil kadar total fenolik dan aktivitas antioksidan daun surian., The extract of surian leaves (Toona sinensis) contains phenolic compounds that have the potential as natural antioxidants. Optimization of the plant harvesting age and solvent concentration (ethanol) is necessary to obtain the best antioxidant activity of surian leaves. This study aimed to examine the effect of variations in tree age and ethanol solvent concentration on the total phenolic content and antioxidant activity of surian leaves from Sumedang using in vitro analysis. The total phenolic content was measured using the Folin-Ciocalteu method, while the antioxidant activity was measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The extract of 34-year-old surian leaves using 96% ethanol solvent had the highest total phenolic content of 392.28 mg GAE/g dry weight and also produced the highest antioxidant capacity of 1130.26 μm TE/g dry weight with the smallest IC50 value compared to other extracts, which was 4.19 μg/mL, indicating that the 34-year-old surian leaf extract using 96% ethanol solvent had the best antioxidant activity. Tree age and ethanol solvent concentration were proven to affect the total phenolic content and antioxidant activity of surian leaves.
Keyword: Antioksidan, kadar fenolik, metode DPPH, Toona Sinensis

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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