The Chemical Composition Of The Four Kinds Of Flowers And Their Antioxidant Activity

Yunnan Province is famous for its flowers, and some of flowers can be used as food or medicine. It is very meaningful to carry out a thorough study of the flowers in Yunnan. Four kinds of flowers, Gladiolus gandavensis, Sophora viciifolia, Caragana sinica and Scindapsus aureus were chosen as the research objects in the current study for their high value in the food and medical fields. Firstly, on the basis of phytochemistry theory and method, the chemical constituents of the aerial part of Gladiolus gandavensis were investigated, and 9 new compounds were obtained. In the second part, three flowers(Sophora viciifolia, Caragana sinica and Scindapsus aureus) were studied to evaluate their antioxidant properties and chemical constituents, respectively. And the chemical compounds which might play the important role for the strong antioxidant activity of these flower, were isolated. This study suggests that these three flowers can provide valuable functional ingredients and can be used for the prevention of diseases related to various oxidant by-products of human metabolism. This thesis includes three chapters:In Chapter 1, the research progress of antioxidant activity was reviewed from the following three aspects:(1) Production and harm of free radicals; (2) Antioxidant activity screening methods; (3) Different types and structure-activity relationship of natural antioxidant.In the chapter 2, the study on the chemical constituents of Gladiolus gandavensis was carried out. Thirty-two compounds, including nine new triterpene saponins were isolated and elucidated from ethanol extract of this plant. These new oleanane-type triterpene saponins glycosidated at C-29 were not obtained frequently.In the chapter 3, based on their chemical constituents, the antioxidant activities of Sophora viciifolia, Caragana sinica and Scindapsus aureus were studied systematically.Firstly, the antioxidant capacities of extracts of Sophora viciifolia flower were evaluated by several test methods (ABTS, DPPH, reducing power, FRAP and inhibition of lipid peroxidant models) for the first time. And the ethyl acetate fraction showed the highest antioxidant activity. Correlation analysis revealed that the flavonoids might be mostly responsible for the antioxidant activity of this flower. In addition, sixteen compounds were isolated from this flower. Luteolin (4) exhibiting good DPPH radical scavenging activity was abundant in this flower (5.56 mg/g dry sample), which implied an important role of luteolin for the antioxidant capacity of Sophora viciifolia flowers. Secondly, twenty-three compounds were isolated from Caragana sinica flower for the first time. Moreover, the antioxidant activities of extracts of this flower were evaluated through several chemical systems (FRAP, DPPH, hydroxyl radical,β-carotene bleaching methods and inhibition of lipid peroxidant models). Ethyl acetate fraction was proved to be the most active antioxidant extract of this flower. And the flavonoids in this flower might contribute to the good antioxidant activity of this flower. The HPLC analysis showed that the compounds of quercetin-3'-O-methyl-3-O-α-L-rhamnopyranos-yl (1→6)-β-D-glucopyranoside (4) and rutin (3), turned out to be the major flavonoids with the concentration of 3.94 mg/g sample and 1.20 mg/g sample, respectively.Thirdly, twenty-six compounds were isolated from Scindapsus aureus flower for the first time. According to the results determined by several in vitro antioxidant models, the ethyl acetate fraction was proved to be the most efficient for antioxidant activity. However, correlation analysis showed less correlation between antioxidant activity and flavonoids. Five powerful antioxidants (phenolics), such as (-)-epi-catechin (8),3-(3, 4-dihydroxyphenyl)-2-propenoic acid methyl ester (14),3-(3,4-dihydroxyphenyl)-E-acrylic acid 1-(3,4- dihydroxyphenyl)-2-methoxycarbonylethy ester (19), catechol (20) and gallic acid (21) were found in the ethyl acetate fraction, suggesting an important role of these compounds for the antioxidant capacity of Scindapsus aureus flower.Fourthly, the comparison of antioxidant activities and antioxidant contents of these three flowers let to the antioxidant capacity order of Sophora viciifolia>Caragana sinica> Scindapsus aureus. And the significant correlations between FRAP and inhibition of lipid peroxidant assay shuggested that the combination of these two methods can be used to quantify antioxidant capacities of these three flowers(Sophora viciifolia, Caragana sinica and Scindapsus aureus) accurately.