Assessment of hydroxyl radical generation and radical scavenging activity of Chinese medicinal herbs using GC-MS.
Aqueous extracts of ten Chinese herbs were evaluated for their radical scavenging activity by a GC-MS method based on the Fenton reaction system. Hydroxylation of salicylate and phenylalanine is widely used as an index of hydroxyl radical formation in vivo and in vitro. A problem associated with quantifying product from such reactions is the generation of complex reaction products that increase background 'noise' and reduce sensitivity for the target product. The aim of this investigation was to develop a GC-MS methodology to assess in vitro hydroxyl radical production. In this method, hydroxyl radical was trapped by p-hydroxyphenylacetic acid to form 3,4-dihydroxyphenylacetic acid (DOPAC) which was then selectively extracted from the reaction mixture using aluminium oxide and assayed by GC-MS. Selective adsorption and desorption of the catechol nucleus from aluminium oxide was shown to eliminate interference from non-catechol reaction products effectively. This system was applied to examine the hydroxyl radical scavenging activity of different herbal extracts. The results showed that the herb Dimocaepus Longan Lour exhibited the highest radical scavenging activity of all the herbs examined. With the use of a stable isotope-labelled internal standard, this system could be readily applied to in vitro methods which use 4-hydroxybenzoic acid as a substrate for the hydroxyl radical.
Bioanalytical Mass Spectrometry Facility, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.
Xiaosuo
X
Wang
George A
GA
Smythe
D015102:3,4-Dihydroxyphenylacetic Acid / Q000737:chemistry / Q000378:metabolism; D004365:Drugs, Chinese Herbal / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D017665:Hydroxyl Radical / Q000378:metabolism*; D008550:Melatonin / Q000378:metabolism; D028321:Plant Preparations / Q000737:chemistry*
D004365:Drugs, Chinese Herbal; D016166:Free Radical Scavengers; D028321:Plant Preparations; D015102:3,4-Dihydroxyphenylacetic Acid; D017665:Hydroxyl Radical; D008550:Melatonin