Study On The Hypolipidemic Activity Of The Principal Component Of Malus Rockii

This thesis summarizes the research work in four chapters during my master’s period.Chapter one: the in vitro hypolipidemic activity screening among 364 kinds of plants in western Yunnan;Chapter two: the study on Malus rockii’s chemical composition;Chapter three: the study on the hypolipidemic activity of the principal component of Malus rockii;Chapter four: the review on the chemical composition and pharmacological activities of Malus.Objective: To search for the new natural hypolipidemic compounds from plants and explore the pharmacological mechanism,bringing it into practice that develops the abundant medicinal plant resources in western Yunnan.Methods: The lipid accumulation in Hep G2 cells was induced by different proportions of oleic acid and sodium palmitate for establishing the high-fat model to test the lipid-lowering activity of medicinal plants collected from West Yunnan and compounds isolated and identified from Malus rockii in vitro.The cells was stained with oil red,and the OD value of oil red was determined by enzyme-labeled instrument,the lipid-lowering activity was evaluated by the lipid-lowering rate.Extracts from the twigs and leaves of Malus rockii were isolated and purified by column chromatography and thin-layer chromatography,and their structures were identified through modern spectroscopy techniques.The high fat golden Syrian hamster model by feeding high fat diet was used to evaluate the hypolipidemic activity of phloridzin in vivo and its mechanism of action.Results:1.A total of 364 plant samples were selected.And 43 plant samples,accounting for 11.8% of the total tested samples,had a lipid-lowering rate of more than 15%,while 105 plant samples,accounting for 28.8% of the total tested samples,had a lipid-lowering rate of more than 10%.Samples 0049 AE,0054BE and 0315 CE rated the highest lipid-lowering activity at(20.46 ± 7.72)%,(20.15 ± 11.32)%,(30.07 ±6.74)% respectively.2.Eight compounds were isolated from the Fr.A fraction of 95% ethanol extract of Malus rockii,one compound isolated from the Fr.E and Fr.F fractions.They were identified as phloridzin(1),β-amyrin acetate(2),friedelin(3),3-epifriedelinol(4),lupeol(5),β-sitosterol(6),kakoul(7),3β-hydroxyglutin-5-ene(8),stearyl alcohol(9).The results showed that compound 1 had the lipid-lowering activity in vitro with the final concentrations of 100,200,300 and 400 μM,and the lipid-lowering rates were(2.76 ± 3.64)%,(9.64 ± 6.26)%,(3.89 ± 3.02)% and(5.75 ± 4.70)%,respectively.And compound 1 exhibited the highest lipid-lowering activity at 200 μM.3.Phloridzin,the principal component of Malus rockii,can significantly reduce the concentrations of TC,TG,LDL-C and HDL-C in serum with no significant decrease in TC,TG,LDL-C and HDL-C in liver.The results of organ index and pathological section showed that phloridzin had no toxic effect on any organs.Both200 mg/kg and 50 mg/kg phloridzin groups could significantly improve the liver fatty lesions of hyperlipidemic hamsters,and the safety of various organs and hematological indexes of the hamsters is higher than that of lovastatin.Network pharmacology and molecular docking simulation showed that phloridzin had good affinity with cholesterol 7-alpha hydroxylase(CYP7A1).Western blot analysis showed that phloridzin could significantly increase the expression of CYP7A1 protein in the liver of hyperlipidemic hamsters.Conclusion:1.Among 364 plant samples,105 showed lipid-lowering activity in vitro,and the lipid-lowering rate was more than 10%.Sample 0315 CE had the best lipid-lowering activity.2.Nine compounds were isolated and identified from Malus rockii,including five triterpenoids,one dihydrochalcone,one stigmasterol and two other compounds of which the main component was phloridzin.Compounds 2,4,6 and 8 were isolated from Malus for the first time,and compounds 2-9 were isolated from the plant for the first time.The results of in vitro lipid-lowering activity showed that compound 1 had the lipid-lowering activity at the final concentration of 100,200,300 and 400 μM.The lipid-lowering activity at 200 μM was similar to that of simvastatin,and slightly stronger than that of lovastatin.Compound 5 showed weak in vitro lipid-lowering activity at the final concentration of 200 μM,while compounds 2-4,6-9 showed no lipid-lowering activity in vitro at the final concentration of 200 μM.3.The overall performance of the anti-hyperlipidemia effect of the phloridzin from the M.rockii is possibly better than that of lovastatin,and its target is probably CYP7A1.