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: Query Expansion based on Bilingual Dictionary Using Conditional Probability
Abstrak: Query expansion is a technique that can be used to bridge vocabulary gaps between queries and documents in the collection. With query expansion, user will be helped to formulate queries well so that user will optimize the search result. In this study, the expansion term was resulted from the translation of bilingual dictionary. Subsequently, several terms of expansion were elected based on the closeness of its relationship with the original query. This research showed that conditional probability can be used to select expansion term in bilingual translation method query expansion. The result of 1000 documents was more than 97% relevan document can be retrieved by this system. The more expansion term used, the larger number relevan document was retrieved.
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