Studies On The Antioxidation Activities Of Hsian-tsao (Mesona Procumbens Hemsl.)

The herb Mesona procumbens Hemsl., called Hsian-tsao(Ht) in China, as animportant plant in the Orient, has high medicinal value. Ht has various activecomponents, polyphenol compounds, polysaccharides, ascorbic acid, tocopherol and soon. Several studies have indicated that the antioxidant activities of some fruits andvegetables were highly correlated to their total polyphenol contents. Aiming at thepolyphenol compounds, extraction and separation of polyphenol compounds from Htand the main antioxidant behavior were investigated.First，extraction of polyphenol compounds from Hsian-tsao (Mesona procumbensHemsl.) with acetone, ethanol and methanol at three different concentrations (50%,75%and100%), and purification of polyphenol compounds by macroporous resincolumn chromatography, HPLC and preparative HPLC were investigated. Polyphenolcontent (PC) was determined by the Folin-Ciocalteu assay (FC), and the inhibition oflipid peroxidation was determined by the ferric thiocyanate method (FTC). The resultsshowed that, in comparison with other solvents,75%acetone solvent was the mosteffective for extraction of polyphenol compounds, and can achieve both the highestconcentration and the most effective structure of polyphenol compounds. The75%acetone extract (PC:190.9mg GAE/g extract) was purified further by AB-8adsorptioncolumn chromatography. A～H eight fractions were obtained, and the most effectivefraction E had the highest polyphenol content (PC:534.9mg GAE/g E) and the highestinhibition(76%), even larger than gallic acid (47%) at the same concentration.Moreover, the fraction E was separated into four polyphenol compounds (1～4) byHPLC and each compound reached a purity of more than98%. The structure of thecompound was identified by MS and NMR, and the compound4was determined to beastragalin (a flavonol glycoside) which is separated from Ht for the first time.Second，the antioxidant activities of75%acetone extract and the fraction E wereinvestigated to study the main antioxidant behavior of Ht. The antioxidant activities,reducing power, Fe2+-chelating ability and DPPH radical-scavenging ability as well as inhibition of lipid peroxidation were studied. Different positive controls (BHT, GA,EDTA, Vitamin C) were used in the measurement. Results indicated75ACEE and Ewere electron donors, and the fraction E with high polyphenol content had higherantioxidant activity than75ACEE. And it seemed that both75ACEE and fraction Ewere more effective in inhibition of lipid peroxidation and DPPH radical-scavengingability than Fe2+-chelating ability from a comparison of IC50. The main antioxidantbehavior of Ht was that in antioxidant system, Ht was as a strong electron donor or afree radical scavenger.In all, during the separation of polyphenol compounds from75ACEE, the fractionE was obtained firstly, which had high PC, good antioxidant activity and low cost.Especially in antioxidant system, fraction E will be as a strong electron donor or a freeradical scavenger. Therefore it is of no doubt that E has a splendid perspective.Secondly, four active components were obtained, and astragalin is separated from Htfor the first time.