Judul: Kinetika Inhibisi Ekstrak Sidaguri (Sida rhombifolia L) terhadap Xantina Oksidase secara Elektrokimia
Abstrak: Uric acid is final product of purine metabolism. Abnormal conditions of uric acid metabolism will cause precipitation of sodium urate crystals in joints, a condition termed gout. Xanthine oxidase (XO) is an enzyme that plays an important role in purine metabolism and functions to catalyze hypoxanthine oxidation into xanthine and, xanthine into uric acid. The well known xanthine oxidase inhibitors (XOIs) is allopurinol, which is one option out of the many synthetic drugs used in modern medicine for the treatment of gout. Nevertheless, the use of allopurinol can cause side effects such as allergies, fever, and gastrointestinal disorders. The side effects of synthetic drug use such as allopurinol have prompted people to turn to traditional medicine that utilizes herbs (medicinal herbs). Sida rhombifolia is one of the traditional medicinal plant with potential as anti-gout. The previous research showed that flavonoids crude extract from this plant could in vitro inhibit the activity of xanthine oxidase up to 71% and the kinetic study by spectrophotometric resulted that the type of flavonoids crude extract inhibition was a competitive inhibition. The purpose of research was to investigate the type of inhibition kinetics of S. Rhombifolia’s ethanol extract by electrochemical method and to compare the study of linearity and sensitivity between electrochemical and spectrophotometric methods. The determination of inhibition kinetics type which is formed can subsequently explain the inhibitory mechanism formed and describe the affinity formed between XO enzyme as a target with drug candidate compounds, whether it is temporary (competitive inhibition and uncompetitive inhibition) or permanent (non-competitive inhibition). The results showed that the yield of S. Rhombifolia’s ethanol extract was 9.82% with the inhibition activity of 13.64% to 82.69% (5.00-200 ppm) and the value of IC50 was 91.15±5.74 ppm. Allopurinol as a control showed the inhibition activity of 15.26-70.95% (0.10-4.00 ppm) and the value of IC50 was 2.45±2.21 ppm. Inibition kinetic of the ethanol extract caused a change of KM (0.187 mM or increase 68.73%) and unchange of Vmax. Based on the data, the type of inhibition kinetic was a competitive inhibition, that had the value of inhibitor affinity (α) of 3.18. The inhibitor affinity value (α) of the enzyme can be determined by calculating the ratio between the value of KM with inhibitors and KM values without inhibitor. Linearity of xanthine oxidase activity assay by electrochemical and spectrophotometric methods showed the range of 0.01-1.00 mM and 0.05-0.70 mM respectively. The sensitivity of electrochemical method was reported higher (0.95 μA mM-1) than the spectrophotometric method (0.007 min-1).
Keyword: electrochemistry, inhibition kinetics, Sida rhombifolia L, xanthine oxidase

Judul: Kinetika Inhibisi Ekstrak Tempuyung (Sonchus arvensis) terhadap Xantina Oksidase secara Elektrokimia.
Abstrak: Tempuyung (Sonchus arvensis) adalah tanaman obat tradisional yang telah diketahui potensinya sebagai antiasam urat melalui penghambatan kinerja xantina oksidase (XO). Penelitian ini bertujuan menentukan kondisi optimum aktivitas XO, menentukan daya inhibisi dan IC50 berbagai inhibitor, serta menentukan tipe kinetika inhibisi ekstrak terhadap XO secara elektrokimia. Aktivitas enzim XO diukur pada kondisi optimumnya, yaitu suhu 25 ± 3 °C, pH 7.5, dan konsentrasi xantina 1.40 mM. Hasil yang diperoleh menunjukkan bahwa ekstrak memiliki daya inhibisi 41.99% sampai 91.66% pada konsentrasi 50–500 μg/mL dengan nilai IC50 115.84 μg/mL. Sementara itu, allopurinol sebagai kontrol positif dan Urafit® sebagai pembanding memiliki daya inhibisi yang lebih tinggi, masing-masing dengan nilai IC50 3.17 μg/mL dan 69.75 μg/mL. Inhibisi ekstrak menunjukkan tipe kinetika inhibisi kompetitif karena mengakibatkan nilai KM meningkat dan nilai Vmaks tetap. Selain itu, ekstrak memiliki afinitas yang cukup kuat terhadap XO (α: 3.34), dengan senyawa aktif dugaan yang berasal dari golongan flavonoid berdasarkan analisis kandungan fitokimia dan profil kromatografi lapis tipis.
Keyword: kinetika inhibisi, metode elektrokimia, Sonchus arvensis, xantina oksidase

Judul: PEmetaan Kawasan Peka Bencana Tsunami di wilayah Pesisir propinsi Nusa Tenggara Timur
Abstrak: Kondisi geologi Indonesia yang merupakan pertemuan lempeng-lempeng tektonik menjadi kawasan Indonesia memiliki tingkat kerawanan yang tinggi terhadap bencana alam seperti gempa bumi, tsunami dan rawan letusan gunung api. Gempa bumi yang terjadi di dasar laut mengakibatkan pergolakan massa air yang dapat menghasilkan gelombang besar atau disebut tsunami.
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