Study On The Chemical Constituents And Biological Activities Of Lobelia Davidii Franch.

Objective:The purpose of this research is to systematically study the chemical constituents and biological activities of Lobelia davidii Franch.,and provide a theoretical basis for the development and utilization of L.davidii resources.Methods:The whole plants of L.davidii were dried and crushed,extracted under refluxing with 75%ethanol and then partitioned with Et OAc and n-Bu OH successively.The ethanol extract of L.davidii were successively fractionated by silica gel column chromatography,MCI chromatography,Sephadex LH-20 column chromatography and further purified by semi-preparative HPLC to obtained the compounds.The structures of the compounds were identified by NMR,MS,IR,UV and specific rotation data,and the absolute configuration of compounds was determined by ECD spectrum.Some compounds were selected to assess cytotoxic activities to the human non-small-cell lung cancer A549 cells,and screening for neuroprotective activity of PC12 by MTT assay.The inhibitory activity of tyrosinase was screened by L-dopa oxidation method.Theα-glycosidase inhibitory activity was determined by PNPG assay.Moreover,the DPPH and ABTS methods were used to screen the free radical scavenging activities.Results:A total of 31 compounds were isolated and identified from the ethyl acetate fractions of L.davidii,including7 triterpenoids,2 steroids,5 polyacetylenes,3alkaloids,3 lignans,7 glycosides and 4 other compounds.Compounds 1,10 were new compounds,and compound 15 was a new natural compound.Compounds 3,6-7,14,16-31 were isolated from L.davidii for the first time.The screening results showed that compounds 1 and 6 had certain inhibitory activity for the A549 cells with the IC₅₀ value of 26.72±2.05μM and 36.70±3.43μM.The screening results of neuroprotective activity showed that compounds 13,14 and 15 had strong protective activity against corticosterone-induced PC12 cell damage at 40μM.Compounds 12,19,20 exhibted moderate inhibitory activities against corticosterone-induced PC12 cell damage at 40μM.The inhibitory activity screening of tyrosinase showed that the isolated compounds had no obvious inhibitory activity on tyrosinase.While compounds 2,4 and 17 had strong inhibitory activities againstα-glycosidase,and compounds 1,27 exhibted moderate inhibitory activities againstα-glycosidase,respectively,which were higher than that of acarbose(IC₅₀=249.55±2.26μM).The results of antioxidant activity showed that compound 18 had high intensity DPPH free radical scavenging activity with the IC₅₀ value of 1.27±0.15μM,which were higher than that of V_C(IC₅₀=3.29±0.63μM).Compounds 19,20 and 30 exhibted moderate free radical scavenging activity against DPPH.ABTS radical scavenging assay showed that compound 20 had strong intensity ABTS free radical scavenging activity with the IC₅₀ value of 0.16±0.06μM,which was better than V_E(IC₅₀=5.80±0.96μM).Compounds 18,19,30 had moderate free radical scavenging ability on ABTS with the IC₅₀ value of 6.15±0.41μM,11.54±1.16μM and 12.08±1.24μM.Compound 27 had weak intensity ABTS free radical scavenging activity with the IC₅₀ value of 53.74±2.03μM.Conclusions:The results of this paper provide an important material basis for the chemical and biological activities of L.davidii,and provided a scientific theoretical basis for further development of antitumor,neuroprotective,hypoglycemic and antioxidant drugs.