Study On Chemical Compositions Of The Stems And Leaves Of Panax Noto-ginseng And Their Biological Activity

Panax notoginseng（Burk.）F.H.Chen,a plant of the Panax genus,family Ara-liaceae,is the best-known famous traditional Chinese medicinal herb in Yunnan Prov-ince.P.notoginseng is mostly used as a dry root into medicine.The stems and leaves of P.notoginseng are also known as P.notoginseng leaves（PNL）.PNL are regarded as an accessory of P.notoginseng,with high annual output but extremely low utiliza-tion rate.Studies have shown that the rare saponins in PNL still play important physi-ological roles in calming and soothing the nevers,and have been used to develop Chi-nese patent medicines such as“Qiyeshenan tablets”.In 2016,the Yunnan Provincial Government approved notoginseng flowers,stems,and leaves as raw materials for local specialty food and issued local food safety standards.With the discovery of the pharmacological activity and edible value of PNL,it is becoming more commonly used in the development of health food,which can improve the utilization rate of re-sources.PNL have been recognized as a rich source of saponins,flavonoids,volatile oils,organic acids,polysaccharides and so on.Among them,the saponins are mainly pro-topanaxadiol saponins（PPDs）,such as ginsenosides Rb₁,Rb₃,Rd,gypenoside IX,notoginsenosides Fa and Fc.With the continuous development of separation techno-logy,more and more rare saponins with changed side chains have been discovered in recent years.Unlike chemical and physical transformation methods,most of the new compounds still retain complete sugar chains（particularly C-20 sugar chains）.Ac-cording to the analysis of the structural characteristics of rare saponins,the structural characteristics of rare saponins possess distinctive features that can be categorized as follows:（1）C-24 or C-25 mono-oxidation;（2）C-24,C-25 double oxidation;（3）the side chain is formed into a ring;（4）carbon reduction or split ring rearrangement,etc.However,due to variable sample sources and low content,these components are often uncertain and difficult to isolate and reproduce,resulting in their activity and safety being frequently overlooked.Based on the pre-researches on PNL,the chemical components in PNL were isola-ted and purified under the guidance of mass molecular network and characteristic tar-get fragment ions.By extracting and refining the total saponins of PNL combined with macroporous adsorption resin,silica gel column chromatography,p HPLC sepa-ration and purification methods,and a total of 44 monomer compounds were separat-ed and identified,including 14 new rare saponins with changed side chains:noto-ginsenosides SL₁-SL₁₄（1*-14*）,and 30 known compounds:spathulenol（15）,2,6-dihydroxy-3,4-dimethyl benzoic acid methyl ester（16）,decanoic acid（17）,dienyl acid（18）,falcarinol（19）,notoginsenoside R7（20）,（3β,12β,20ξ,23E）-12,20,25-trihydroxydammar-23-en-3-yl-β-D-glucopyranoside（21）,ginsenoside Rh₃（22）,gin-senoside Rh₂（23）,notoginsenoside SFt₁（24）,ginsenoside-Rh₂₂（25）,notoginsenoside SFt₆（26）,notoginsenoside SFt₇（27）,majoroside-F4（28）,20（S）-ginsenoside Rg₃（29）,ginsenoside Rd（30）,25-hydroxy-23-ene（31）,floralginsenoside O（32）,ginsenoside Rb₃（33）,ginsenoside Rb₂（34）,notoginsenoside NL-E₂（35）,notoginsenoside NL-F1（36）,gypenoside LXXI（37）,quinquenoside L7（38）,notoginsenoside-Ng₄（39）,noto-ginsenoside Rb₁（40）,notoginsenoside NL-B₃（41）,notoginsenoside NL-E₃（42）,no-toginsenoside NL-B₂（43）,notoginsenoside NL-A₃（44）.The rare saponins with altered side chains discovered from PNL are structurally re-lated to the main component saponins.For example,notoginsenosides SL₂₀,SL₂₂ can be regarded as the product of the oxidative reaction of notoginsenoside Fa from PNL.According to the local climatic condition and geographical location of Yunnan,it is speculated that the rare saponins with changes in those side chains are produced by the oxidation of free radicals in the presence of oxygen,ultraviolet rays,chlorophyll and so on.As a result,it is hypothesized that oxidative stress induced by strong UV radiation may lead to oxidation of the double bonds in the main saponins,resulting in changes to the structure of the side chains.PNL is a traditional Chinese medicine used to improve blood circulation,relievepain,and promote overall well-being.Some compounds found in PNL,including rare ginsenosides with side chain changes,have been reported to have neuroprotective ef-fects.Furthermore,the neuroprotective activity of saponins in PNL was studied by in vitro cell experiments to establish a model of L-glutamate-induced nerve cell injury,and the valproic acid（VPA）was used as a positive control.As a result,ginsenoside Rb₁,gypenoside LXXI,notoginsenoside NL-B₂,notoginsenoside SL₁₁,notoginseno-side SL₁₂,（3β,12β,20ξ,23E）-12,20,25-trihydroxydammar-23-en-3-yl-β-D-glucopyranoside,notoginsenoside NL-E₃,floralginsenoside O,and 25-hydroxy-23-ene exhibited light protective effects against L-glutamate-induced nerve cell injury（25μM）.The chemical composition and biological activity of PNL were studied,which not only increases the molecular diversity and biological activity diversity,but also pro-vides a theoretical basis for promoting the rational utilization of P.notoginseng.