title: Optimization of microwave-assisted extraction of polyphenols from herbal teas and evaluation of their in vitro hypochlorous acid scavenging activity.
abstract: Hypochlorous acid (HOCl) is an important reactive oxygen species (ROS) and non-radical and is taking part in physiological processes concerned with the defense of the organism, but there has been limited information regarding its scavenging by polyphenols. This study was designed to examine the HOCl scavenging activity of several polyphenols and microwave-assisted extracts of herbal teas. HOCl scavenging activity has usually been determined spectrophotometrically by a KI/taurine assay at 350 nm. Because some polyphenols (i.e., apigenin and chrysin) have a strong ultraviolet (UV) absorption in this range, their HOCl scavenging activity was alternatively determined without interference using resorcinol (1,3-dihydroxybenzene) as a fluorogenic probe. In the present assay, HOCl induces the chlorination of resorcinol into its non-fluorescent products. Polyphenols as HOCl scavengers inhibit the chlorination of the probe by this species. Thus, the 25% inhibitive concentration (IC25) value of polyphenols was determined using the relative increase in fluorescence intensity of the resorcinol probe. The HOCl scavenging activities of the test compounds decreased in the order: epigallocatechin gallate > quercetin > gallic acid > rutin > catechin > kaempferol. The present study revealed that epigallocatechin gallate (IC25 = 0.1 μM) was the most effective scavenging agent. In addition to polyphenols, four herbal teas were evaluated for their HOCl activity using the resorcinol method. The proposed spectrofluorometric method was practical, rapid, and less open to interferences by absorbing substances in the range of 200-420 nm. The results hint to the possibility of polyphenols having beneficial effects in diseases, such as atherosclerosis, in which HOCl plays a pathogenic role.
authors.affiliation: Department of Chemistry, Faculty of Engineering, Istanbul University , Avcilar, 34320 Istanbul, Turkey.
authors.forename: Burcu
authors.initials: B
authors.lastname: Bekdeşer
authors.forename: Nazan
authors.initials: N
authors.lastname: Durusoy
authors.forename: Mustafa
authors.initials: M
authors.lastname: Özyürek
authors.forename: Kubilay
authors.initials: K
authors.lastname: Güçlü
authors.forename: Reşat
authors.initials: R
authors.lastname: Apak
mesh_terms: D031162:Achillea / Q000737:chemistry* / Q000528:radiation effects; D001628:Beverages / Q000032:analysis*; D028241:Camellia sinensis / Q000737:chemistry* / Q000528:radiation effects; D016166:Free Radical Scavengers / Q000032:analysis / Q000302:isolation & purification*; D006997:Hypochlorous Acid / Q000032:analysis*; D008872:Microwaves; D010936:Plant Extracts / Q000032:analysis / Q000302:isolation & purification*; D059808:Polyphenols / Q000032:analysis / Q000302:isolation & purification*; D017382:Reactive Oxygen Species / Q000032:analysis; D027543:Salvia officinalis / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D016166:Free Radical Scavengers; D010936:Plant Extracts; D059808:Polyphenols; D017382:Reactive Oxygen Species; D006997:Hypochlorous Acid
keywords: flavonoids; herbal teas; hypochlorous acid scavenging activity; microwave-assisted extraction; polyphenols; resorcinol probe; spectrofluorometry