Detection and activity evaluation of radical scavenging compounds by using DPPH free radical and on-line HPLC-DPPH methods

Abstract

The antiradical activity of crude extracts (80% methanol, 20% water) of S. officinalis, S. glutinosa, S. sclarea and S. aethiopis was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging method. For validation of this method several well known antioxidants (ascorbic acid-6-palmitate, gallic, chlorogenic, ferulic, caffeic, uric, gentisic and vanillic acids, catechin, quercetin, epicatechin, phloridzin, rutin and naringin) were investigated additionally. In these experiments ascorbic acid-6-palmitate had highest antiradical activity. Within the group of phenolic acids gentisic acid had the highest antiradical activity comparing with the other tested phenolic acids. Uric acid, vanillic acid, phloridzin and naringin have a much lower antiradical activity. Different reaction kinetics behaviour was observed. The validated DPPH radical scavenging method was applied to the evaluation of the antiradical activity of plant extracts. The Salvia extracts showed very high antiradical activity towards the DPPH·. An on-line HPLC-DPPH method was developed using a methanolic solution of DPPH· for a rapid detection of radical scavenging components after HPLC separation. The HPLC-DPPH on-line method was also applied to a screening of several radical scavenging components in plant extracts as well as for quantitative analysis. The HPLC analysis revealed the presence of several radical scavenging components in the all Salvia extracts. This HPLC-DPPH on-line method can also be used for quantitative determination of radical scavenging compounds.