Judul: Metabolomic Application in Identification α-Glucosidase Inhibitor from Vegetables and Spices
Abstrak: Diabetes mellitus is a degenerative disease with a high prevalence worldwide. Plant-based foods such as vegetables and spices were often reported to be able to reduce the risk of and even cure diabetes mellitus, especially type 2 (T2DM). Indonesia has many natural resources such as vegetables and spices that can be sources of antidiabetic foods. However, the antidiabetic activity of many vegetables and spices have not been evaluated. Besides, studies to observe the bioactive compounds responsible for the antidiabetic activity of vegetables and spices are still limited. One of the antidiabetic activities commonly studied from plant species is the α-glucosidase inhibition. Therefore, the objective of this study was to evaluate the potency of α-glucosidase inhibition of 11 vegetables and 4 spices commonly consumed in Indonesia and to identify their bioactive compound using a metabolomic approach. This study consisted of 3 stages: 1) Screening α-glucosidase inhibition activity of Indonesian vegetables and spices, (2) characterization of antioxidant compound from selected plant (obtained from the first stage) using UHPLC-HRMS and identification of its α-glucosidase inhibitor using NMR- and HPLC combined with UHPLC-HRMS metabolomics, and (3) verification of α-glucosidase inhibition activity of putative compounds (obtained from the second stage) through in silico analysis. The results of the first study showed that the highest antioxidant and α-glucosidase inhibition activity was found in leaves extract of Syzygium polyanthum followed by Pluchea indica with the values of the IC50 antioxidant activity being 2.46 and 4.34 μg/ml, respectively. The values of their IC50 of α-glucosidase inhibition were 11.76 and 12.17 μg/ml, respectively. Interestingly, the total phenolic content of these two samples was also higher than others with 25.37 and 37.99 μg GAE/mg extract, respectively. The 1H-NMR fingerprinting analysis showed that each sample had different spectral profile, especially at the aromatic region (chemical shift (δ) > 5.7). Further metabolite profiling on the 1H-NMR of S. polyanthum revealed the presence of gallic acid, syringic acid, and myricetin, whereas 5-O-caffeoylquinic acid, 4,5-di-O-caffeoylquinic acid methyl ester, and esculetin were found in the 1H-NMR of P. indica. Previous studies reported that all identified compounds had antidiabetic activity especially through α-glucosidase inhibition. Thus, those compounds might be associated with the α-glucosidase inhibition activity of S. polyanthum and P. Indica, which was investigated further in the next step. Based on the results of the first study, S. polyanthum leaves were chosen for the second stage. Dried leaves of S. polyanthum were fractionated using solvents with different polarity sequentially i.e. hexane, combination of hexane-acetone, acetone, combination of acetone-water and water to obtain 14 fractions. Analysis of antioxidant activity through the ability to reduce radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) indicated that at a tested concentration of 500 μg/ml, Fraction 9/F9 (obtained from acetone:water = 4:1) gave the highest antioxidant activity followed by Fraction 1/F1 (obtained from hexane 100%), Fraction 10/F10 (obtained from acetone:water = 3:2) and Fraction 3 (obtained from hexane:acetone = 4:1) with the values of 95.21, 94.82, 93.37 and 93.19%, respectively. The characterization of the UHPLC-HRMS chromatogram of F9 identified the presence of gallic acid, trans-aconitic acid, and myricetin, while only gallic acid and trans-aconitic acid were identified in
Keyword: α-glucosidase, antioxidant, docking, HPLC-UHPLC-HRMS, metabolomics, NMR, Syzygium polyanthum

Judul: In Silico and In Vitro Analysis of α-Glucosidase Inhibition by Ethanol Extract of Red Ginger (Zingiber officinale var.  Rubrum) from Sukabumi
Abstrak: Indonesia menempati peringkat kelima penderita diabetes melitus terbanyak di dunia sehingga perlu adanya pengobatan antidiabetes yang efektif salah satunya dengan mekanisme penghambatan enzim α-glukosidase. Obat antidiabetes sintetik dalam jangka waktu panjang dapat memberikan efek samping. Oleh karena itu, penggunaan obat herbal perlu dilakukan karena dinilai lebih aman. Jahe merah telah banyak dimanfaatkan dalam bidang medis dan diharapkan berpotensi menghambat aktivitas enzim α-glukosidase. Penelitian ini bertujuan mengukur aktivitas inhibisi enzim α-glukosidase oleh ekstrak etanol jahe merah asal Sukabumi dan menentukan ligan terbaik melalui studi in silico. Penelitian ini dilakukan dengan maserasi dalam etanol 70% dan dilakukan pembacaan absorbansi inhibisi enzim, sedangkan studi in silico dilakukan dengan molecular docking. Hasil penelitian menunjukkan nilai IC50 penghambatan enzim α-glukosidase sebesar 50.139,719 ± 0,481 μg/mL dan didapatkan dua ligan terbaik yaitu 6- shogaol dan 6-gingerol yang memiliki nilai ΔG dan Ki mendekati akarbosa (ligan pembanding terbaik), lolos uji toksisitas, serta berinteraksi dengan banyak situs pengikatan dan situs katalitik yang terletak di dalam poket situs aktif, Indonesia is in the fifth position with the most diabetes mellitus sufferers globally, so effective antidiabetic treatment is needed, such as the mechanism of inhibiting the α-glucosidase enzyme. Synthetic antidiabetic drugs, in the long term, can have side effects. Therefore, the use of herbal medicines is necessary because they are considered safer. Red ginger has been widely used in the medical field, and it has expected to have the potential to inhibit the activity of α-glucosidase. This study aimed to measure the inhibitory activity of α-glucosidase enzyme by the ethanol extract of red ginger from Sukabumi and determine the best ligand through in silico study. This research was carried out by maceration in 70% ethanol and reading the absorbance of enzyme inhibition, while in silico studies were carried out by molecular docking. The results showed that the IC50 value for inhibition of α-glucosidase enzyme was 50.139,719 ± 0.481 μg/mL. Two best ligands were obtained, namely 6-shogaol and 6-gingerol, which had ΔG and Ki values close to acarbose (the best comparison ligand), passed toxicity testing and interacted with many binding sites and catalytic sites that were located in active site pocket
Keyword: α-Glucosidase, 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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