Studies On The Flavanoids And Antioxidative Activities Of The Leaves Of Apocynum Venetum L.

Apocynum venetum L. (Apocynaceae), commonly known as Luobuma, is a wild shrub widely distributed in the mid and northwestern China. Traditionally, its leaves have been used for the treatment of hypertension, nephritis, and neurasthenia.In this research, we carried out studies on the flavanoids from leaves of Apocynum venetum L.. By using various kinds of column chromatography (such as silica gel C.C., polyacrylamide C.C. and Sephadex LH-20 C.C), eleven compounds were separated from the H₂O-soluble fraction isolated from the leaves ethanol extract of Apocynum venetum L.. On the basis of physicochemical properties and spectral data, their structures were confirmed. They were elucidated as quercetin (1), isoquercitrin (2), hyperoside (3), quercetin-3-O-(6"-Oacetyl)-β-D-glucopyranoside (4), quercetin-3-O-(6"-O-acetyl)-β-D-galacopyranoside (5), kaemperol(6), kaempferol-3-O-(6"-O-acetyl)-β-D-gl-ucopyranoside(7), kaempferol-7-O-α-L-rhamnopyranoside (8), scopoletin (9). Compound 5 and 8 were isolated from Apocynum for the first time.At the same time, the preparation process of ethanol extracts was investigated by the orthogonal experimental design based on determination of the content of the total flavonoids. The result showed that the optimum extraction conditions were to extract with ten times amount of 50% alcohol by refluxing thrice, 90min each time.Furthermore, the leaves ethanol extract of Apocynum venetum L. and the isolated flavonoids were examined for their free radical scavenging activities using H₂O₂/ Fe²⁺ free radical generation system and peroxynitrite free radical generation system. The ethanol extract and compound 1～7 exhibited significant hydroxyl radical scavenging activities .The ethanol extract and compound 1 and 3 also showed peroxynitrite-scavenging activities. Moreover, the inhibitory effect on lipid-peroxidation in mice liver homogenate induced by H₂O₂/Fe²⁺ free radical generation system of the leaves ethanol extract and compound 1 and 3 were evaluated. The results showed they all had a strong antioxidative activity.In addition, the original plant, the drug material, chemical constituents, pharmacological and clinical studies of Apocynum venetum L. had also reviewed.