Compositional analysis, biological activity, and food protecting ability of ethanolic extract of Quercus infectoria gall

摘要

This study was aimed to investigate chemical composition, biological activity, and food protecting ability of Quercus infectoria gall (QIG).The total content of phenolics, flavonoids, and hydrolyzable tannins was evaluated. Ion and fatty acid compositions of QIG were identified by ion chromatography and gas chromatography flow ionization detector (GC-FID), respectively. Ellagic acid (28,156.85 mg/kg) and catechin (716.21 mg/kg) were predominant. The antioxidant activity of QIG was determined as 2.29, 1.65, 1.52, and 1.98 mmol Trolox equivalent antioxidant capacity (TEAC)/g sample for DPPH, ABTS, FRAP, and CUPRAC analyses, respectively. QIG extract exhibited dose-dependent inhibition on α-glucosidase enzyme with an IC_(50) value of 0.002 mg/ml. QIG displayed antimicrobial activity against selected reference and isolated mixed strains, most notably on Escherichia coli. The addition of QIG extract as a natural preservative to pasteurized cow’s milk resulted in lower total bacterial count (TBC), total yeast-mold count (TYMC), and higher pH compared to control milk.