 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Antioxidant Capacity Assays by Sequential Injection Analysis using a Peristaltic Pump and Low-Cost Amperometric Detection with Pencil Lead Electrodes) ผู้เขียน: Pachara Meanha, Jakkrapun Kongkedsuk, Apisake Hongwitayakorn, Rasamee Chaisuksant สื่อสิ่งพิมพ์:pdf AbstractMiniaturization of electrode and flow cell assemblies was accomplished using low-cost pencil graphite leads and micropipette tips for sequential injection analysis (SIA) with amperometric detection (AD). The Masterflex peristaltic pump of the SIA-AD system was semi-automatically controlled by the in-house electronic circuit controller and pump drive computer software written in the Processing language. The developed SIA-AD was applied to rapid screening tests of antioxidant capacity by 2,2?- azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay and reducing capacity measurement. By ABTS assay, the cathodic current signal of the ABTS cation radicals left after the reaction with the antioxidants in the sample was monitored at the applied potential -0.10 V vs. Ag/AgCl whereas by the reducing power measurement, anodic current from oxidation of antioxidants in the sample at +0.50 V vs. Ag/AgCl was detected. The peak current from each sample assay was calibrated with a gallic acid (GA) antioxidant standard conducted using the same procedure and expressed as the total antioxidant capacity of the sample in equivalent units (GAE). The total antioxidant capacities of some herb infusions were determined by ABTS assay and reducing power measurement using the proposed SIA-AD with sample throughputs of 22 and 36 samples/hr, respectively. Classical spectrophotometric ABTS assay was also carried out for comparison. The total antioxidant capacities in GAE found in the herb samples by all assays were in consensus for the series with black tea >> cinnamon > ginger > safflower ? chrysanthemum. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Antioxidant Capacity and Phenolic Content of Mimusops elengi Fruit Extract) ผู้เขียน:Chaiyan Boonyuen, Sunanta Wangkarn, Oranart Suntornwat, Rasamee Chaisuksant สื่อสิ่งพิมพ์:pdf AbstractThe antioxidant capacities of the phenolic compounds extracted from immature green, mature green and orange ripe fruits of Mimusops elengi were investigated. The compounds were first removed as crude extracts from the fruits using methanol-acetone and then further separated into three different fractions designated as free phenolic acids (F1), soluble phenolic esters (F2) and insoluble phenolic acid esters (F3). The antioxidant capacity of each fraction was determined by radical scavenging (DPPH and ABTS) assays. The antioxidant capacity values of these fractions, expressed as gallic acid equivalents (GAE) by ABTS assay for immature and mature fruits were in the range of 13.5 ? 0.1 - 441.7 ? 4.8 mg/ g extract with relative capacities being F2 > F3 > F1. The GAE values for ripe fruits were in the range of 192.3 ? 1.0 – 212.5 ? 4.6 mg/g extract with relative values of F2 ? F3 > F1. The antioxidant capacity of the crude extract from immature fruit (GAE = 318.5 ? 12.3 mg/g extract) was higher than that of either the mature (GAE = 234.1 ? 9.2 mg/g extract) or the ripe fruit (GAE = 111.9 ? 4.9 mg/g extract) at p = 0.05. High performance liquid chromatographic analysis confirmed that all phenolic fractions contained gallic acid as a constituent. The total phenolic contents determined by the Folin-Denis assay were consistent with the antioxidant capacity. From the results, Mimusops elengi fruits appeared to be a good source of natural antioxidant. |