Judul: Aktivitas Antioksidan Fraksi Teraktif Buah dan Daun Asam
Abstrak: Tamarind plant (Tamarindus indica) contain tannins, flavonoids, and saponins which are usually have antioxidant activity. The purpose of this study was to determine antioxidant activity and total phenolic content of the most active fraction of tamarind fruits and leaves. Antioxidant activity was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging method and total phenolic content by Folin-Ciocalteu method. The result showed that the most active fraction of tamarind fruits and leaves had IC50 value of 293.22 mg/L and 57.89 mg/L, respectively. These results were higher compared to ascorbic acid as positive control which was 2.12 mg/L. Total phenolic content of the most active fraction of tamarind fruits and leaves was 100.48 mg gallic acid equivalent/100 g dry fruits and 107.44 mg gallic acid equivalent/100 g dry leaves, respectively. The most active fraction of tamarind leaves had higher antioxidant activity compared to its fruit, however both fractions were lower compared to ascorbic acid.
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Judul: Penentuan Fraksi Aktif Ekstrak Daun Jambu Biji (Psidium Guajava) Sebagai Antioksidan
Abstrak: Ekstrak daun jambu biji mempunyai kandungan metabolit sekunder yang berperan aktif sebagai antioksidan untuk menangkal radikal bebas dalam tubuh. Penelitian ini bertujuan menetapkan fraksi aktif ekstrak daun jambu biji yang berperan mengurangi radikal bebas dari 1,1-difenil-2-pikrilhidrazil (DPPH). Aktivitas antioksidan ditentukan berdasarkan nilai IC50 yang diperoleh dari nilai penangkapan radikal bebas DPPH. Sampel diekstraksi menggunakan pelarut etil asetat, metanol dan etanol 70% (v/v) untuk memperoleh ekstrak kasar. Hasil penelitian menunjukkan simplisia daun jambu biji mengandung flavonoid, tanin, alkaloid, saponin, dan steroid. Standar kontrol positif antioksidan yang digunakan adalah asam askorbat dan kuersetin. Ekstrak kasar yang mempunyai aktivitas antioksidan paling kuat adalah ekstrak etanol 70% (v/v). Fraksionasi ekstrak etanol 70% (v/v) dengan kolom kromatografi menghasilkan 7 fraksi. Fraksi dengan aktivitas antioksidan teraktif adalah fraksi ke 3. Nilai IC50 ekstrak dan fraksi teraktif etanol 70% (v/v) masih lebih rendah dari pada standar yang digunakan, tapi termasuk mempunyai aktivitas sangat kuat karena nilainya kurang dari 50 mg/L.
Keyword: antioksidan, DPPH, fraksionasi, IC50, daun jambu biji

Judul: Zero-inflated negative binomial models in small area estimation.
Abstrak: The problem of over-dispersion in Poisson data is usually solved by introducing prior distributions which lead to negative binomial models. Poisson data sometime is also suffered by excess zero problems, a condition when data contains too many zero or exceeds the distribution's expectation. Zero Inflated Negative Binomial (ZINB) method can be utilized to solve such problems. This paper demonstrates the adaption of ZINB methods in Small Area Estimation with excess zero data. It is shown that the excess zero problem has substantially influenced the Empirical Bayes (EB) estimates, and the adaption of ZINB methods has improved the precision and reliability of the estimates. Key Words: Small Area Estimation, Zero-Inflation, Poisson-Gamma, Negative Binomial Regression, Empirical Bayes
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