Judul: Total Flavonoids, Antioxidant Capacity, and Compound Identification of Red Ginger (Zingiber officinale var. rubrum) Extract from Sukabumi
Abstrak: Jahe Merah (Zingiber officinale var. rubrum) dikenal sebagai tanaman tradisional yang dimanfaatkan sebagai obat. Salah satu potensi dari jahe merah sebagai antioksidan karena adanya kandungan metabolit sekunder berupa senyawa flavonoid. Metode ekstraksi dan pelarut yang digunakan perlu diperhatikan untuk memperoleh hasil senyawa antioksidan dari ekstrak jahe merah asal Sukabumi. Penelitian ini bertujuan menentukan total flavonoid, kapasitas antioksidan, dan identifikasi senyawa dari ekstrak etanol serta ekstrak air jahe merah asal Sukabumi. Ekstraksi dilakukan dengan metode maserasi. Ekstrak dari kedua pelarut masing-masing diukur kadar total flavonoid serta kapasitas antioksidan dengan metode FRAP. Hasil penelitian menunjukkan ekstrak etanol memiliki nilai total flavonoid dan kapasitas antioksidan lebih tinggi sebesar 5,99 mg QE/g dan 473,93 µmol TE/g dibanding ekstrak air 3,73 mg QE/g dan 206,75 µmol TE/g. Uji lanjutan ekstrak etanol kemudian dianalisis menggunakan LC-MS/MS yang menghasilkan 22 senyawa aktif seperti golongan fenolik dan terpenoid. Kedua golongan tersebut memberikan kapasitas antioksidan yang tinggi di jahe merah asal Sukabumi., Red ginger (Zingiber officinale var. rubrum) is known as a traditional plant that is used as medicine. One of the potentials of red ginger as an antioxidant is that it contains secondary metabolites in the form of flavonoid compounds. The extraction method and solvent used need to be considered to obtain antioxidant compounds from red ginger extract from Sukabumi. This research aimed to determine total flavonoids, antioxidant capacity, and identify compounds from the ethanol extract and water extract of red ginger from Sukabumi. Extraction is carried out using the maceration method. Extracts from both solvents were each measured for total flavonoid content and antioxidant capacity using the FRAP method. The results showed that the ethanol extract had a higher total flavonoid and antioxidant capacity value of 5.99 mg QE/g and 473.93 µmol TE/g compared to the water extract of 3.73 mg QE/g and 206.75 µmol TE/g. Further tests of the ethanol extract were then analyzed using LC-MS/MS, which produced 22 active compounds such as phenolics and terpenoids. These two groups provide high antioxidant capacity in red ginger from Sukabumi.
Keyword: antioxidant, flavonoids, red ginger, solvent, LC-MS/MS

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: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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