Judul: Penapisan Ekstrak Daun Famili Zingiberaceae Sebagai Inhibitor Tirosinase Dan Antioksidan
Abstrak: Penapisan atas daun Zingiberaceae telah dilakukan sebagai inhibitor tirosinase dan antioksidan. Kadar total antosianin, klorofil, karotenoid, tanin, dan flavonoid ditentukan menggunakan metode spektroskopi. Metode penapisan antioksidan menggunakan 1,1-difenil-2-pikril hidrazil (DPPH) dan penapisan inhibitor tirosinase menggunakan substrat L-tirosina (monofenolase) dan L-DOPA (difenolase). Ekstrak metanol daun temulawak (Curcuma xanthorrhiza) lebih aktif sebagai antioksidan daripada ekstrak lainnya dengan nilai IC50 281.85 mg/L dan hubungannya dengan kadar tanin ialah 22.76%. Ekstrak etil asetat dari daun bangle hantu (Zingiber purpureum) memiliki aktivitas inhibisi monofenolase 82.86% dan hubungannya dengan kadar karotenoid ialah 52.02%. Ekstrak etil asetat daun temu putih (Curcuma zedoaria) memiliki aktivitas inhibisi difenolase 90.20% dan hubungannya dengan kadar flavonoid ialah 39%. Jadi, dari 10 daun spesies Zingiberaceae, temulawak lebih berpotensi sebagai antioksidan, sementara bangle hantu dan temu putih lebih berpotensi sebagai inhibitor tirosinase.
Keyword: antioksidan, inhibitor tirosinase, penapisan, Zingiberaceae

Judul: Daun Pelindung Bunga Temu Lawak (Curcuma xanthorriza Roxb.) sebagai Inhibitor Tirosinase dan Antioksidan
Abstrak: The utilization a bract flower of temu lawak (C. xanthorrhiza) as tyrosinase inhibitor and antioxidant was verified by identifying its active compound. Sample of a bract flower of temu lawak was extracted with n-hexane, ethyl acetate, and methanol as well as distillation of its essential oil. Tyrosinase inhibition (monophenolase and diphenolase) and antioxidant (diphenylpicryl hydrazyl (DPPH) method) assays were performed on various extracts and essential oil of the sample. The ethyl acetate extract was the active extract with IC50 1.97 mg/mL on monophenolase, 1.57 mg/mL on diphenolase and 12.68 μg/mL on antioxidant. The ethyl acetate extract that was fractionated with column chromatography (CC) produced 12 fractions. F12 was the most active fraction from fractionation by CC that might contain flavonol-related compound based on infrared spectrophotometer analysis and phytochemical assay. A fraction with the highest yield (F1) continued fractionation by preparative thin layer chromatography (TLC) produced 2 fractions. F1.2 was the more active fraction resulted F1 fractionation using preparative TLC which might contain auron-type compound based on infrared spectrophotometer analysis and phytochemical assay
Keyword: antioxidant, Curcuma xanthorrhiza, tyrosinase inhibitor, fractionation

Judul: Dynamics Model for Rural and Urban Economic Growth
Abstrak: Lewis theory of structural change has focused on mechanisms that allow countries to transform their domestic economic structure to a more modern economy. The proposed model deals with the mechanism of interaction between rural and urban Economic. This model is concerned with the process of labor transfer from rural to urban areas. This study aims to model the dynamics of economic growth in rural and urban areas, including determining the equilibrium solution and to carry out simulation of the model. The simulation results show that the transfer of labor from rural to urban areas will increase the rate of change of capital so that structural changes can be realized. In addition, increased propensity to save in rural areas will also accelerate structural change
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