Judul: Identification of Antidiabetic Compounds in Karamunting Leaves (Melastoma malabathricum L.) with Metabolomic and Molecular Docking Approaches and Their Potential as Functional Drinks
Abstrak: Diabetes is a metabolic disease characterized by a high blood glucose level on fasting, which is above 126 mg/dL. Type-2 diabetes mellitus (T2D) was dominant (90%) among three types of diabetes (type-1 diabetes mellitus, type-2 diabetes mellitus, and gestational diabetes mellitus). Hyperglycemic conditions characterize the T2D traits as the result of abnormalities in insulin secretion and activity. These conditions may trigger the accumulation of free radicals. Therefore, consuming food with antihyperglycemic and antioxidant therapies might be a recommendation for DT2 patients’ treatments. Handling of DT2 sufferers can be done by consuming foods that contain antihyperglycemic and antioxidants, including karamunting (M. malabathricum) leaves which the people of West Kalimantan have often used as herbal tea given to diabetics, which is brewed with hot water. One of the taste described by the community from the brewed water of karamunting leaves (ASDK) is astringency. Previous studies have proven the antidiabetic activity of karamunting leaves by in vivo testing of ethanol and methanol extracts. Chemical compounds that act as antidiabetic, their application in diabetic animal models, and the sensory profile of the karamunting leaves, especially when consumed in brewing water, have not been reported. This study has the general objectives of identifying bioactive antidiabetic compounds with the metabolomic method, knowing the mechanism of antidiabetic in vivo using diabetic animal models, and evaluating the effect of various forms of brewing karamunting leaves (Melastoma malabathricum) on sensory profiles by analyzing multivariate (sensometric) data and their antidiabetic activity. The study was divided into three steps as follows: 1) Obtaining an LC-MS/ MS-based fingerprint profile from water extract of karamunting leaves, identifying antidiabetic bioactive compounds (antihyperglycemic and antioxidant) from brewed water of karamantung leaves with a metabolomic approach based on LC-MS/MS and molecular docking methods, and determining the best brewing conditions for karamunting leaves, and; 2) Studying the mechanism of ASDK antidiabetic activity with diabetic animal models; and: 3) Identifying and mapping the ASDK based on their sensory attributes using the sensometric method. Our study was initiated by analyzing the fingerprint profile based on LC-MS/MS, antioxidant activity (DPPH), and toxicity (brine shrimp lethality test / BSLT) of the water extract of karamunting leaves at various extraction conditions with water temperature (room temperature and hot temperature at room temperature). 90 ± 2 ºC) and different times (15, 30, 45 minutes). Six compounds namely, 4-O-caffeoylquinic acid, quercimeritin, digiprolactone, 3-O-trans-couma-roylquinic acid, norbergenin, and arteamisinine I were identified in the aqueous extract of karamunting leaves. Karamunting leaf water extract with hot water (90 ± 2 ºC) at a low dry leave:water ratio (5:100 w/v) for 15 minutes has high antioxidant activity and low toxicity. Therefore, brewing with hot water and a brewing time of under 15 minutes, i.e., 5 minutes, was used for further experiments. Furthermore, the LC-MS/MS profiles of the ASDK obtained from twelve different brewing conditions (with or without ultrasonication; dry leave:water ratio of 20:100, 7:100, and 3:100 (w/v); brewing times of 5 and 15 minutes) were used as variables in the identification stage of antidiabetic compounds. (antihyperglycemic and antioxi-dant) with a metabolomic approach. The antihyperglycemic activity was carried out in vivo
Keyword: antioxidant, antihyperglycemic, brewed water of karamunting leaf, hot brew, sensometrics

Judul: Phytochemical Profile, Antioxidant, and Antidiabetic Activity of Bidara Laut Wood Water Extract
Abstrak: Pengobatan diabetes melitus dengan obat sintetis memiliki efek samping, sehingga dikembangkan obat alami dari kayu bidara laut (KBL). Penelitian ini bertujuan menentukan rendemen dan kandungan fitokimia serta menganalisis aktivitas antioksidan dan antidiabetes ekstrak air KBL. Ekstrak air KBL diperoleh dari ekstraksi KBL berdiameter kecil/ KBLK (7-10 cm) dan berdiameter besar/KBLB (14-20 cm) skala pilot dengan metode maserasi menggunakan pelarut air. Ekstrak dianalisis fitokimianya dengan Liquid Chromatography–Mass Spectrometry (LC-MS) kemudian diuji secara in vitro aktivitas antioksidan dengan metode DPPH dan antidiabetes dengan metode penghambatan α-glukosidase. Rendemen ekstrak KBLK dan KBLB berturut-turut sebesar 0,88% dan 1,55%. Senyawa fitokimia yang terdeteksi di dalam ekstrak KBLK sebanyak 24 senyawa dan KBLB sebanyak 34 senyawa. Aktivitas antioksidan ekstrak air KBLB tergolong sedang (nilai IC50 147,477 µg/mL), sedangkan ekstrak KBLK tergolong lemah (nilai IC50 220,318 µg/mL). Ekstrak air KBL tidak berpotensi memiliki aktivitas antidiabetes karena pada konsentrasi ekstrak 900 ppm, persentase penghambatan enzim α-glukosidase ekstrak KBLB hanya 13,587% dan KBLK hanya 12,812%., Treating diabetes mellitus with synthetic drugs has side effects, so a natural medicine was developed from bidara laut wood (KBL). This study aims to determine the yield and phytochemical content and analyze the antioxidant and antidiabetic activity of KBL water extract. KBL water extract was obtained from pilot scale extraction of KBL small diameter/ KBLK (7-10 cm) and large diameter/KBLB (14-20 cm) by maceration method using water solvent. The extract was analyzed for their phytochemistry by Liquid Chromatography-Mass Spectrometry (LC-MS) and then tested in vitro for antioxidant activity by the DPPH method and antidiabetic activity by the α-glucosidase inhibition method. KBLK and KBLB extracts yielded 0,88% and 1,55%, respectively. The phytochemical compounds detected in the KBLK extract were 24 compounds and KBLB 34 compounds. The antioxidant activity of KBLB water extract is classified as moderate (IC50 value 147,477 µg/mL), while KBLK extract is classified as weak (IC50 value 220,318 µg/mL). KBL water extract does not have the potential to have antidiabetic activity because at an extract concentration of 900 ppm, the percentage of inhibition of the α-glucosidase enzyme of KBLB extract is only 13,587% and KBLK is only 12,812%.
Keyword: α-glucosidase, DPPH, LC-MS, Strychnos ligustrina

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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