Studies On Antioxidative Activity Of Prunella Vulgaris L. Extracts

Prunella vulgaris.L is a kind of perennial herbs and belongs to mint family. It is one ofthe traditional Chinese medicines. It has documented that Prunella vulgaris can scavenge freeradicals, defer senility, but this research was not deep. In the present study, the antioxidantsubstances of Prunella Vulgaris were extracted by organic solvent method. Theradical-scavenging activity, chelating ability and reducing power of four kinds of extracts ofPrunella Vulgaris were investigated, together with contents of effective substances. Then wediscussed the relationship between antioxidant activities and effective substances. The resultsobtained are as follows:(1) In the present study,5different antioxidant tests were employed in order to evaluatethe antioxidant activities of extracts. They are DPPH radical-scavenging activity, superoxideradical-scavenging activity, Hydroxyl radical-scavenging activity, chelating ability andreducing capacity.The same extract may show different antioxidant ability in differentantioxidant tests because of various mechanisms.(2) All the extracts exhibited some degree of DPPH radical-scavenging activity,superoxide radical-scavenging activity and hydroxyl radical-scavenging activity in aconcentration-dependent manner. When the concentration reached the certain value, theradical-scavenging didn't grow any more. If scavenging ability expressed by IC50value, ethylacetate had the highest scavenging ability, followed by n-butyl alcohol. Water extract andcrude polysaccharide had low scavenging ability.(3)Crude polysaccharide and water extracts showed the same excellent chelating abilityin a concentration-dependent manner. The chelating ability of n-butyl alcohol extract was low,and ethyl acetate extract did not show any chelating effect.(4)All these extracts showed some degree of reducing capacity in aconcentration-dependent manner. Reducing power were in descending order: BHT﹥ethylacetate﹥n-butyl alcohol﹥water﹥crude polysaccharide.(5)The highest content of total flavonoids was found in ethyl acetate extract, and the value was14.45±0.16mg/g. The content of total flavonoids of n-butyl alcohol extract was notas good as ethyl acetate extract, whereas that of water extract and crude polysaccharide weremuch smaller. The highest content of total polysaccharide was found in crude polysaccharide,followed with water extract, whereas that of ethyl acetate extract and n-butyl alcohol extractwere much smaller.(6)There were good correlations between DPPH radical-scavenging activity, hydroxylradical-scavenging activity, superoxide radical-scavenging activity, reducing power and totalflavonoids content. Correlation coefficients were0.56-0.95, basic in strong correlation range.These results illustrated that flavonoids are very important antioxidant substances of PrunellaVulgaris L.. There were correlations between superoxide radical-scavenging activity, hydroxylradical-scavenging activity, chelating ability and polysaccharide content. Correlationcoefficients were0.55-0.71, basic in strong or middle correlation range.These results illustrated that polysaccharide occupies a very important place in antioxidantactivity, but not as important as flavonoids.