In vitro antioxidant and antimicrobial activities of the extract of Pericarpium Citri Reticulatae of a new Citrus cultivar and its main flavonoids

To provide the base for the application of a new cultivar of Citrus reticulata Blanco, whose family is Rutaceae, a flavonoid extract of Pericarpium Citri Reticulatae (FEPCR), the dried rind of the ripe citrus, was obtained with 80% aq. ethanol. Total flavonoid content of FEPCR was determined by a colorimetric method. Total phenol content was estimated as gallic acid equivalents. The major constituents of FEPCR, including Hesperidin, Nobiletin and Tangeretin, were determined by HPLC analysis. The antioxidant activities of FEPCR, Hesperidin, Nobiletin and Tangeretin were evaluated by various antioxidant assays, including DPPH scavenging, hydroxyl radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging and reducing power. All samples showed antioxidant activities to some degree in all the tested methods. In addition to the antioxidant activity, the antimicrobial assay was measured as well. Six strains of microorganisms including Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Salmonella typhi and Enterobacter cloacae were used in the tests. FEPCR and Hesperidin displayed a broad antimicrobial spectrum and exerted antimicrobial effects in antimicrobial tests. But Tangeretin and Nobiletin exhibited low antimicrobial activities.