| Medicago sativa L. is perennial leguminous plant, and conventional folk medicinal herb, It can be used to clear spleen and stomach, clear away the heat-evil and expel superficial evils, benefit to internal organs. But Medicago sativa L. is more widely applied to pasture, or is producted into many kinds of fodder. With the development and application of plant resources, the researches of alfalfa mainly concentrated in the leaf protein, saponin and polysaccharide, the other chemical constituents was less reported. Especially, study on the tannin and the antioxidative activities of effective chemical components in Medicago sativa L. has never been reported.In chapter one, Medicago sativa L.'s studying, tannin, volatile oil, fibrin, metallic elements, antioxidative activities were reviewed.In Chapter two, the tannin in Medicago sativa L.'s extraction and ultraviolet spectrophotometer conditions were studied. In the 756 nm, there was a good linear relationship in the range of 2.04-12.24μg/mL, the standard equation was Y=35.38x+0.0069, the correlation coefficient was 0.9993, the average recovery was 95.32% -103.3%. Tannin extraction conditions were the concentration of hydrochloric acid was 2.5%, the concentration of ethanol was 70%, temperature was 50℃, regurgitant time was 5h, the ratio of extraction was 2.15 mg / g.In Chapter three, extracting process of Leaf protein in Medicago sativa L. was optimized. Through the single factor and orthogonal experiment, the main factor which can mostly influence the extracting process of Leaf protein was solid-liquid ratio, the conditions were solid-liquid ratio was 1:20, the concentration of NaCl was 1%, flocculating time was 5 min, and pH was 2.5. content of calcium in the Medicago sativa L.which removed Leaf protein was 1.85%. Then water-soluble dietary fiber was extracted from Medicago sativa L. which was brown powder. Through the single factor and orthogonal experiment water-soluble dietary fiber was extracted from the Medicago sativa L. which was extracted the protein and Medicago sativa L. which was not extracted the protein. the conditions were solid-liquid ratio was 1:75, and immerge time was 10 hours, extracted at 70℃and pH was 2.5, the extraction ratio of water-soluble dietary fiber was 4.43% and 4.51%. extraction rate of water-soluble dietary fiber in Medicago sativa L. which was not extracted the protein was slightly higher than that of the Medicago sativa L. which was extracted the protein.In Chapter four, after wet-digested sample, the contents of ten metallic elements were established by flame atomic absorption spectrometry. Medicago sativa L. contains a wealth of calcium, magnesium, iron and cobalt. And Ca was 1.8×10~4 mg / kg; Mg was 1.28×10~3 mg / kg; Fe was1.82×10~2mg/kg; Co was 1.45×10~2 mg / kg. After extraction the leaf protein, water-soluble dietary fiber, the content of calcium changes a little.In Chapter five, the chemical components of volatile oil and fatty acid from Medicago sativa L. were analyzed by GC-MS. the volatile oil was extracted by steamdistillation. 53 compounds were identified and the amount of components account for 95.6% of all the volatile oil. The main components include: aldehyde accounts for 26.06% of all the volatile oil, ketong accounts for 14.57% of all the volatile oil, alcohol compounds 14.02%, aromatic hydrocarbon compounds 12.14%, heterocyclics compounds 9.25% and so on. petroleum ether as solvent, fatty acid extracted from Medicago sativa L. seeds, 11 compounds were identified and the amount of components account for 86.71% of all the fatty acid. Unsaturated fatty acid compounds of 62.31%.In Chapter six, The antioxidant abilities of different extractions of Medicago sativa L. were evaluated by scavenging active free radical and reducing power, The results indicated that EAF showed the strongest antioxidant activity among extractions; EF's scavenging activity was stronger than WF's. At the same time , the antioxidant activities of Medicago sativa L'ethanol extraction, grape leaves'ethanol extraction and pomegranate leaves'ethanol extraction were compared.In chapter seven some pieces of advice and idea were proposed for future's work.
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