Judul: Identifikasi dan Potensi Antioksidan Flavonoid Kulit Kayu Mahoni (Swietenia macrophylla King)
Abstrak: Mahogany bark as wood processing industrial waste has not widely used compared to other parts of mahogany. This research was conducted to identify the flavonoids from mahogany bark and its role as an antioxidant. Antioxidant activity of mahogany bark’s extract was measured by using two methods namely diphenil-1.1-2-picrylhydrazyl (DPPH) method and tiobarbituric acid (TBA) method. Identification of flavonoids (quersetin) was performed by using HPLC and TLC. Antioxidant activity of flavonoids (quersetin) was measured by using DPPH method.Inhibition activity of mahogany bark’s extract on DPPH method for the extraction of methanol, n-hexane, diethyl ether, ethyl acetate, vitamin E (positive control) and water at concentrations of 50 ppm are respectively for 81.33%, 12.74%, 23:40%, 65.54 %, 30.42%, and 68.04%. The inhibition activity of mahogany bark’s extract on TBA methods for methanol fraction 200, 100, 50 ppm was 59.81%, 59.02%, 58.96%. Extraction of water 200, 100, 50 ppm was 54.65%, 49.01%, 43.09%. Vitamin E 200, 100, 50 ppm was 40.91%, 36.48%, 27.15%. Kuersetin content in the sample is 16 mg/100g sample. Inhibition activity of antioxidants on kuersetin as 50, 100, and 200 ppm for 87.2%, 89.1%, 92.8%.
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Judul: Aktivitas Antioksidan dan Penghambatan α-Glukosidase Ekstrak dan Nanopartikel Ekstrak Kulit Kayu Mahoni (Swietenia macrophylla King)
Abstrak: Mahogany (Swietenia macrophylla King) bark is waste disposal industry manufacture of bark. Mahogany bark have catechin, epicatechin, and swietemacrophyllanin contents which useful as an antioxidants and antidiabetic of rats induced alloxan. This study aimed to determine the antioxidant activity and inhibition of α-glucosidase in the extract and nanoparticle extract of mahogany bark. Extraction method use aquades as solution, antioxidant activity assays was caried using 2,2-diphenyl-1-picrilhidrazyl (DPPH) and reducing power. Inhbition of α-glucosidase was measured with a spectrophotometric method. Mahogany moisture content was 4.87%. Extract yield of 9.46% and yield of nanoparticle 51.11% were obtained. The DPPH resulted that of the rutin compound, extract, and nanoparticles obtained by IC50 DPPH method sequentially 17.33 ± 1.17 ppm, 9.62 ± 0.72 ppm, and more than 2500 ppm. Respectively, power reduction of the rutin compound has a 67.03% at 25 ppm, the extract 67.41% at 20 ppm, and nanoparticle 31.47% at 20 ppm. IC50 values inhibition of α-glucosidase extract was 17.25 ppm, nanoparticles were more than 200 ppm, and acarbose was 0.37 ppm. The test results showed that the extract capable of acting as antioxidant and antidiabetic based on IC50 values. As for nanoparticles mahogany bark extract did not able to act as antioxidants and antidiabetics based on the method tested.
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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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