Study On Chemical Constituents And Biological Activities Of Pogostemon Esquirolii And Tylophora Floribunda

Natural product is an important source of new drug development.It has always been a incessantly pursuit of researchers to discover lead compounds with novel structures and outstanding activities from natural products.This study implemented a systematically study on chemical constituents of Pogostemon esquirolii from Labiatae family and Tylophora floribunda from Asclepiadaceae family as well as anti-inflammatory and antibacterial activities of the isolated compounds.In the study on chemical constituents,the solvent extraction method was adopted.The herbs powder was soaked in 95%ethanol to obtained the crude ethanol extract,and then the ethanol extract was initially fractionated and enriched by application of extraction methods.Using macroporous resin,MCI gel,silica gel,Sephadex LH-20 gel,C₁₈reversed-phase silica gel column chromatography,preparative thin layer chromatography and semi-preparative high performance liquid chromatography,each faction was finely separated and purified to obtain pure compounds.By means of IR,UV,NMR,HR-MS,ECD and other spectral methods as well as X-ray single crystal diffraction analysis,the structures of isolated compounds were identified and characterized.A total of twenty-two compounds were isolated from Pogostemon esquirolii,of which ten were new compounds（1-10）,including eight eudesmane-type sesquiterpenoids（1-8）,one bisabolane-type sesquiterpenoid（10）and one other sesquiterpenoid（9）.Known compounds included:two caryolane sesquiterpenoids（11,12）,an elemane sesquiterpenoid（13）,a guaiane sesquiterpenoid（14）,and a chain diterpenoid（15）;as well as two oleanane triterpenoids（16,17）,four isoflavones（18-21）,and a long-chain fatty acid（22）.This is the first study on chemical constituents of Pogostemon esquirolii.All compounds（1-22）were isolated from Pogostemon esquirolii for the first time.Sesquiterpenoid with bisabolane-type skeleton was reported from the Pogostemon genus for the first time.On the other hand,eight compounds were isolated from Tylophora floribunda,of which two were new pregnane-type compounds（23,24）.23 is a sugar-free14,15-seco-pregnane-type steroid with a novel[5,6,6,5,5,5]skeleton,and 24 is a new14,15-seco-18-nor-pregnane-type steroidal glycoside.Other known compounds include a13,14:14,15-diseco-pregnane-type steroidal glycoside（25）,and five other compounds（26-30）.Compounds 23-25 and 27-29 were isolated from Tylophora floribunda for the first time.In this study,the anti-inflammatory activities of isolated compounds 1-25 on LPS-induced BV2 microglia neuroinflammation model were tested.As a result,compounds6,9,11,12,16-21 from Pogostemon esquirolii and 24 from Tylophora floribunda were found to inhibit the production of nitric oxide（NO）with inhibition rate between 14.6%to68.3%on LPS-induced BV2 cells at a concentration of 20μM.In addition,the minimum inhibitory concentration（MIC）test against Staphylococcus aureus and Escherichia coli was conducted on the isolated compounds 1,4-5,8-25.The results showed that a prenylated isoflavone 20（licoricidin）had a MIC of 16μM against S.aureus,which disclosed that 20 possesses good antibacterial activity.