Judul: Flavonoid of Zanthoxylum achanthopodium Fruit as an Antioxidant and α-Glucosidase Inhibitors
Abstrak: Diabetes Mellitus could be caused by the presence of free radicals which damaged the pancreas cell membrane. Previous research showed that extract of andaliman (Zanthoxylum acantophodium DC.) fruit possessed activity as antioxidant. However, there has been no scientific report concerning its activities as antidiabetic. The main objective of this research was to evaluate the in vitro mechanism of Z. acantophodium fruit extract as antioxidant and α-glucosidase inhibitor. Andaliman macerated by four solvents, namely n-hexane, ethyl acetate, methanol and water, as solvent for extraction. Antioxidant activity was measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azinobis -3- ethylbenzathiazolin -6-sulfonic acid (ABTS) method, and inhibition of enzyme α-glucosidase using substrate p-nitrofeyl-α-D-glucopyranoside. Results of this research showed that methanol extract had the highest activities, both as antioxidant and α-glucosidase inhibitor. This extract was separated by column chromatography yielded six fractions (A-F). The most active fraction as α-glucosidase inhibitor was fraction C and for antioxidant was fraction E. These two fractions were further separated using preparative thin layer chromatography. The best antioxidants with DPPH method was fraction E2 (IC50 137.46 ppm), for ABTS method was crude methanol extract (IC50 30.04 ppm), while for α-glucosidase inhibitors was the fraction C (IC50 16 ppm). Based on the results of data analysis by Infrared and UV-Vis, showed that the main active compound contained in fraction C2 and E2 were the of aurones and flavanones of flavanoid group.
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Judul: α-Glucosidase Inhibition Activity and DPPH Free Radical Scavenging from Stratified Aqueous Extract of Red Ginger (Zingiber officinale Roxb. var Rubrum)
Abstrak: Jahe merah (Zingiber officinale Roxb. var. Rubrum) mengandung senyawa fenolik yang berpotensi menurunkan kadar glukosa darah (antihiperglikemik) pada pasien diabetes melitus. Penelitian ini bertujuan menentukan aktivitas inhibisi α-glukosidase, aktivitas antioksidan dalam meredam radikal bebas DPPH, dan kadar total fenolik ekstrak air jahe merah bertingkat (ekstrak ke-1, ekstrak residu ke-1, dan ekstrak residu ke-2). Metode penelitian yaitu ekstraksi jahe merah secara infundasi serta analisis dengan teknik uji spektronanometer yang meliputi analisis antidiabetes melalui aktivitas inhibisi α-glukosidase, aktivitas antioksidan metode DPPH, dan kadar total fenolik metode Folin-Ciocalteu. Aktivitas inhibisi α-glukosidase dan kadar total fenolik memiliki perbedaan nilai yang signifikan (p<0.05) dengan nilai tertinggi 97.729% (ekstrak ke-1) dan 27.624 mg GAE/g ekstrak (ekstrak residu ke-2). Aktivitas antioksidan dalam meredam radikal bebas DPPH memiliki perbedaan nilai yang tidak signifikan dengan nilai tertinggi 4.682 mg AAE/g ekstrak (ekstrak residu ke-1). Hasil analisis menunjukkan nilai aktivitas inhibisi α-glukosidase dan kadar fenolik total berbeda signifikan (p<0,05) dengan nilai tertinggi 97.729% (ekstrak ke-1) dan 27.624 mg GAE/g ekstrak (ekstrak residu ke-2). Hasil aktivitas antioksidan memiliki nilai yang tidak berbeda nyata (p>0,05) dengan nilai tertinggi 4.682 mg AAE/g ekstrak (ekstrak residu ke-1)., Red ginger (Zingiber officinale Roxb. var. Rubrum) contains phenolic compounds that have potential to reduce blood glucose levels (antihyperglycemic) in patients with diabetes mellitus. This study aimed to determine the inhibitory activity toward α-glucosidase, antioxidant activity in reducing DPPH free radicals, and total phenolic content from stratified aqueous extract of red ginger (1st extract, 1st residue extract, and 2nd residue extract). The red ginger was extracted by infundation and analyzed by spectronanometer test techniques which included analysis of antidiabetic through inhibitory activity of α-glucosidase, antioxidant activity using the DPPH method, and total phenolic content using the Folin-Ciocalteu method. The results of the analysis showed that the inhibitory activity of α-glucosidase and total phenolic content were significantly different (p<0.05) with the highest values 97.729% (1st extract) and 27.624 mg GAE/g extract (2nd residue extract). The result of antioxidant activity was not significantly different (p>0.05) with the highest value 4.682 mg AAE/g extract (1st residue extract).
Keyword: α-Glucosidase, Antioxidant, Diabetes Mellitus, Red Ginger

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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