Study On The Active Antioxidative Constituents Of The Lespedeza Virgata

The genus Lespedeza (Leguminosae) has about 60 species distributingfrom east Asia to northeast of Australia and in north America. The wholeplants were used in the treatment of acute and chronic nephritis, azothemia,diuresis. It is reported that previously isolated constituents from this plantshowed a strong antioxidative activity. Non-toxic antioxidants are desired foruse as food additives and medical substances.This thesis dealed with the extraction and systematic isolation ofLespedeza virgata(Thunb.)DC., as well as the structure elucidation of thecompounds isolated from this plant. Especially, to study the chemicalconstituents of Lespedeza virgata(Thunb.)DC., both modern and traditionalisolation and purification technics were utilized on silica gel columnchromatography, polyamide column chromatography, Sephadex LH-20 andthin layer chromatography etc.. The structures were elucidated by usingultraviolet, electrospray ionization-mass spectrometry and assigned in detailby nuclear magnetic resonance spectral analysis. Six compounds weredetermined as 5-hydroxy-6-methyl-2'-methoxy-[(6″,6″-dimethylpyrano(2″,3″: 7,8)] [6′″,6′″-dimethylpyrano(2′″,3′″:4',5')]-(2S)flavonone(â… ), Kaempferol-3-O-α-L-rhamnoside(â…¡), Kaempferol-3-O-β-D-glucoside(â…¢), Quercetin-3-O-α-L-rhamnoside(â…£), Kaempferol-3, 7-O-α-L-dirhamnoside(â…¤) and Quercetin-7-O-β-D-glucoside(â…¥), respectively. Compoundâ… was found as a novelcompound. Both Compoundâ… ,â…¢andâ…£were firstly found in the genus ofLespedeza.In the structure elucidating of these compounds, IR, MS as well as 1Dand 2D NMR techniques such as ¹H-NMR, ¹³C-NMR, DEPT, HSQC, HMBC,¹H-¹H COSY, DEPT 135 and NOESY experiment were used.Moreover, super performance liquid chromatography-mass spectrometrymethod was developed for the analysis and identification.In our studies of natural antioxidants, the methanolic extract of the wholeplants of Lespedeza virgata (Thunb.) DC. showed a strong antioxidativeactivity. Compoundâ… showed the highest antioxidative activity with 95.79%O₂^- scavenging activity. The other sequence of antioxidative activity was:CompoundⅣ＞CompoundⅥ＞CompoundⅢ＞CompoundⅡ＞Compoundâ…¤.Mn(â…¡) complex with quercetin has been prepared and analysised by UVspectra techniques,. It is shown that quercetin Mn(II) complex has reactionactivity with superoxede ion, as indicated by inhibition of pyrogallolautoxidation. It provides the potential SOD-like activity of Mn(â…¡) complexwith flavonoids.