Alkaloids From The Twigs And Leaves Of Flueggea Suffruticosa

The plant Flueggea suffruticosa（Pall.）Baill.,belonging to family Euphorbiaceae,is widely distributed in most areas of China except northwest regions.The whole plant of F.suffruticosa,including roots,flowers,twigs and leaves,is used as Chinese folk medicine for the treatment of rheumatism,hemiplegia,and neurasthenia.Previous phytochemical investigations on this plant had resulted in the isolation of a number of indolizidine alkaloids,named Securinega alkaloids.Some alkaloids had been reported to show significant biological activities on central nervous system,antivirus and cytotoxicity.In the course of our search for structural unique and biologically interesting compounds from the plants of genus Flueggea,we had reported the isolation of a series of new Securinega alkaloids from Flueggea virosa.As a part of our ongoing program,we carried out the extensive phytochemical investigation on the twigs and leaves of F.suffruticosa.As a result,forty-one alkaloids were isolated.Their structures were elucidated by physic-chemical properties,spectroscopic analyses and chemical methods.These compounds were identified as secutisine A（FSL-1）,secutisine B（FSL-2）,secutisine C（FSL-3）,secuacylamine A（FSL-4）,secuacylamine B（FSL-5）,secuacylamine C（FSL-6）,secuacylamine D（FSL-7）,secuacylamine E（FSL-8）,secupyrroline A（FSL-9）,secupyrroline B（FSL-10）,secuproline A（FSL-11）,secuproline B（FSL-12）,viroallosecurinine（FSL-13）,15?-methoxy-14,15-dihydroviroallosecurinine（FSL-14）,15β-hydroxy-14,15-dihydroviroallosecurinine（FSL-15）,3?-hydroxysecurinine（FSL-16）,securinine（FSL-17）,securitinine（FSL-18）,15β-methoxy-14,15-dihydrosecurinine（FSL-19）,secu’amamine C（FSL-20）,phyllanthidine（FSL-21）,4?-hydroxyphyllanthidine（FSL-22）,phyllanthidine B（FSL-23）,secu’amamine（FSL-24）,secupiperine A（FSL-25）,secupiperine B（FSL-26）,secu’amamine F（FSL-27）,secu’amamine E（FSL-28）,virosine B（FSL-29）,securinol A（FSL-30）,virosaine C（FSL-31）,norsecuamine A（FSL-32）,secupyritine A（FSL-33）,secupyritine B（FSL-34）,secupyritine C（FSL-35）,seculactine A（FSL-36）,seculactine B（FSL-37）,seculactine C（FSL-38）,seculactine D（FSL-39）,seculactaminine A（FSL-40）and methyl 6,7,8,9-tetrahydropyrido[1,2-a]indole-10-carboxylate（FSL-41）,respectively.Among them,FSL-1～FSL-12,FSL-15～FSL-16,FSL-22,FSL-25～FSL-26 and FSL-31～FSL-40 are twenty-seven new compounds.Compounds FSL-1～FSL-3 are three novel Securinega alkaloids featuring an unprecedented polycyclic carbon skeleton with additional conjugated ring system at C-2 and C-3.Compounds FSL-4～FSL-8 are five novel dimeric alkaloids connected via long carbon chain.Compounds FSL-33～FSL-35 represent a class of novel pyridoquinolizidine alkaloids incorporating an unusual 11-oxa-2-azatricyclo[4.4.3.0^1,6]tridecane motif.On the basis of our research results and literatures,the hypothetical biogenetic pathways for new alkaloids FSL-1～FSL-3 and FSL-33～FSL-35 were proposed,respectively.The abilities of the isolated alkaloids to promote Neuro-2a cell differentiation were also discussed.Some alkaloids showed potent activities on regulating the morphology of Neuro-2a cells.