| The antioxidant substances of M.platypetala, M.chapensis, M.foveolata and M.maudiae of four years were extracted by organic solvent method. Granularity, extraction temperature and extraction time were selected as three factors to design the orthogonal experiment, and the optimum conditions of extraction were obtained.The components were analyzed by chemical colorimetric method, ultraviolet absorption spectrum and GC/MS. The antioxidant activitiy of ethanol extracts and different solvent extracts of Michelia of four species was studied in vitro, and the synergism of ethanol extract of M.chapensis with phytic acid, propyl gallate, ascorbic acid and citric acid was studied at the same time in the experiment. The main conclusions were as follows:(1)The optimum extraction conditions determined by orthogonal experiment were as follows: granularity 20 eyes, extraction temperature 90℃and extraction time 18 hours.(2)The results showed that the ethanol extracts of Mechlia of four speices contained phenolic compounds and flavonoids. 42 compounds in M.platypetala were indentified and the main components were terpeniods and alcohol. 42 compounds in M.chapensis were indentified and the main components were aromatic and terpenoids. 52 compounds in M.foveolata and the main components were aromatic and alcohol. 21 compounds in M.maudiae were indentified and the main components were aromatic and terpenoids.(3)The antioxidant activity of ethanol extracts of Mechlia of four species was evaluated in vitro by various antioxidant systems, including free radical scavenging, reducing power and lipid peroxidation inhibition, and antioxidant activitiy of ethanol extracts of Mechlia of four species was compared with standard antioxidants such as phytic acid (PA) and propyl gallate (PG)in all antioxidant systems. The researchs showed that the extracts have powerful antioxidant activity in all antioxidant systems, and the antioxidant activity increases with increasing the concentration of samples.The oxidation protection factor of the extracts was between 1 and 2 in edible oil systems. The results showed that the extracts have antioxidant activity to soybean oil, sunflower seed oil and lard.The antioxidant activity of extracts was comprehensive evaluated, and the order of antioxidant activity decreasing was M.chapensis, M.platypetala, M.maudiae and M.foveolata.(4) The results showed that the three solvent extracts of Mechlia of four species have antioxidant activity in all antioxidant systems except petroleum ether extracts of M.platypetala, M.chapensis and M.maudiae. All extraxts were comprehensive evaluated, and the result showed that petroleum ether extract of M.foveolata had the best antioxidant activity, but ethanol extracts of M.platypetal, M.chapensis and M.maudiae have the best antioxidant activity. Therefore, ethanol was choosen as the best extraction solvent. (5) propyl gallate,ascorbic acid and citric acid have synergism to the ethanol extracts of M.chapensis in all antioxidant systems. phytic acid had synergism to the ethanol extracts of M.chapensis in all antioxidant systems except superoxide anion free radical system and DPPH·free radical system.
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