Judul: Identification of Tannins from Sawmill as a Potenstial Vegetable Tanning Agent
Abstrak: Tanin merupakan senyawa polifenol hasil metabolit sekunder dari kulit kayu tanaman dan berfungsi sebagai bahan penyamak nabati. Penelitian ini bertujuan mengidentifikasi kandungan tanin dan jenis tanin, mengetahui kadar tanin total dan kadar flavonoid pada limbah kulit kayu, serta memilih kulit kayu potensial sebagai bahan penyamak. Senyawa tanin diuji secara kualitatif dan kuantitatif. Identifikasi kualitatif menggunakan uji FeCl3, larutan gelatin, kalium ferisianida + ammonia, asam asetat + Pb asetat, dan uji pereaksi Stiasny. Identifikasi kuantitatif menggunakan metode permanganometri dan pengeringan. Uji kualitatif menunjukkan delapan dari dua belas jenis kulit kayu teridentifikasi positif mengandung tanin. Delapan jenis kulit kayu tersebut adalah, kayu mangium, mahoni, sengon, afrika, mindi, kweni, kecapi, dan puspa. Empat jenis kulit kayu lainnya yang negatif adalah kayu lame, kisampang, nangka dan karet. Hasil uji kuantitatif tanin total secara berurut untuk kayu mangiun, mahoni, sengon, afrika, mindi, kweni, kecapi, dan puspa adalah 56,03%; 27,58%; 21,70%; 7,15%; 14,11%; 17,72%; 16,76%; dan 16,52% dan nilai flavonoidnya berturut-turut adalah 21,90%; 13,81%; 8,92%; 6,11%; 5,55%; 5,94%; 11,76%; dan 4,46%. Hasil uji statistik two way anova menghasilkan nilai sig. 0,00 <0,05, menunjukkan terdapat perbedaan hasil kualitas kayu berdasarkan jenis kayu, jenis uji flavonoid/tanin, dan terdapat interaksi antara jenis kayu dengan uji flovonoid/tanin dalam menentukan kayu., Tanins are polyphenol compounds produced by secondary metabolism from plant bark and function as vegetable taning materials. This study aimed to identify the tanin content and type of tanin, to determine the total tanin content and flavonoid levels in the bark waste, and to select potential bark as a taning material. Tanins were tested qualitatively and quantitatively. Qualitative identification used the FeCl3 test, gelatin solution, potassium + ammonia, acetic acid + Pb acetate, and the Stiasny reagent test. Quantitative identification used permanganometric and drying methods. The qualitative test showed that eight of the twelve types of bark were identified as positive for tanin. The eight types of bark were mangium, mahogany, sengon, africa, mindi, kweni, kecapi, and puspa. The other four barks were negative for tanin tests, i.e. lame, kisampang, jackfruit and karet. Total tanin quantitative test results in sequence for mangium, mahogany, sengon, africa, mindi, kweni, kecapi, and puspa wood barks were 56.03%, 27.58%, 21.70%, 7.15%, 14.11%, 17.72%, 16.76%, and 16.52%, respectively. The flavonoid values of the barks were 21.90%, 13.81%, 8.92%, 6.11%, 5.55%, 5.94%, 11.76%, and 4.46%, respectively. The two way ANOVA statistical test resulted in a sig. 0.00 < 0.05, indicating that there were differences in the results of wood quality based on wood type, type of flavonoid / tanin test, and there was an interaction between wood species and the flovonoid / tanin test in determining wood.
Keyword: Flavonoid, Kualitatif, Kuantitatif, Kulit Kayu, Tanin

Judul: Identifikasi dan Potensi Antioksidan Flavonoid Kulit Kayu Mahoni (Swietenia macrophylla King)
Abstrak: Mahogany bark as wood processing industrial waste has not widely used compared to other parts of mahogany. This research was conducted to identify the flavonoids from mahogany bark and its role as an antioxidant. Antioxidant activity of mahogany bark’s extract was measured by using two methods namely diphenil-1.1-2-picrylhydrazyl (DPPH) method and tiobarbituric acid (TBA) method. Identification of flavonoids (quersetin) was performed by using HPLC and TLC. Antioxidant activity of flavonoids (quersetin) was measured by using DPPH method.Inhibition activity of mahogany bark’s extract on DPPH method for the extraction of methanol, n-hexane, diethyl ether, ethyl acetate, vitamin E (positive control) and water at concentrations of 50 ppm are respectively for 81.33%, 12.74%, 23:40%, 65.54 %, 30.42%, and 68.04%. The inhibition activity of mahogany bark’s extract on TBA methods for methanol fraction 200, 100, 50 ppm was 59.81%, 59.02%, 58.96%. Extraction of water 200, 100, 50 ppm was 54.65%, 49.01%, 43.09%. Vitamin E 200, 100, 50 ppm was 40.91%, 36.48%, 27.15%. Kuersetin content in the sample is 16 mg/100g sample. Inhibition activity of antioxidants on kuersetin as 50, 100, and 200 ppm for 87.2%, 89.1%, 92.8%.
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Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model