Discovery And Formation Of Novel Small Molecule Natural Product Gels And Their Application In Drug Delivery

Natural products are natural compounds produced by secondary metabolism of organisms.Due to its excellent pharmacological activity and good biocompatibility,natural products have been widely used as functional active ingredients in the fields of medicine,food and cosmetics.However,the current research on the self-assembly function of natural products and its development as a material is scarce.In the study of chemical composition of traditional Chinese medicine(TCM)FULING(Poria cocos),we observed a series of abnormal experimental phenomena,namely "jelly-like" substances.Studies on"jelly-like"substances have confirmed that they are caused by small molecule natural products with self-assembly capabilities,namely natural product gelators(NPGs).Such natural products can form a soft matter-natural product gels(NPG)-by self-assembly with a solvent.In this dissertation,the small-molecule self-assembled natural products discovered from organisms(TCM)are studied,and the research based on natural product chemistry,super-molecular chemistry and material chemistry is carried out.These studies are a meaningful exploration for the development of new functions and applications of natural products.The main work of this dissertation includes the discovery,formation of novel NPG and their application in drug delivery.First,by reproducing the phenomenon of"jelly-like"substances,the crude extract components of the two gel properties were determined.Using a variety of column chromatography techniques,the two crude extract components were further tracked under the guidance of gel activity,and two responsible compounds were obtained.The structures of compounds 1 and 2 were determined to be poricoic acid A(1)and dehydrotrametenolic acid(2),respectively,by a combination of UV,MS,IR and NMR techniques.Based on the gel determination basis and classification basis(through macroscopic state and rheological properties of"jelly-like"substances,and the type,size and cross-linking mode of the responsible compound),the"jelly-like"substance was finally identified as a physically cross-linked natural small molecule gels,i.e.,NPG.Inspired by the discovery of new NPGs from Poria cocos,a method for obtaining NPGs was proposed.That is,a crude extract having gel ability was screened from the organism(TCM),and the crude extract was subjected to follow-up isolation to obtain new NPGs.The feasibility of the above method was verified using 63 commercially available organisms(TCM).The results showed that 16 of the 63 crude extracts had gel ability.The tracking and isolation of 5 representative crude extracts finally yield 4 new NPGs:3(lupeol from Taraxacum mongolicum),4(diosgenin from Dioscorea nipponica),5(ergosterol from Pleurotus ostreatus)and 6(gastrodin,from Gastrodia elata).The discovery of NPGs 1-6 extended the types of existing NPGs from 2 category 2 types to 3 category 7 types and provided an important material basis for the study of different types of NPG.Then,based on the basic theory of thermodynamics of liquids,we propose new insights into gel formation and explain"why gel".That is,the process of gelation is considered to be a process in which solvent molecules are bound to a certain position in a small ordered region for a long time.This new insight can help us think about what gel from solvent perspective.Based on the above new insights and discovered polycyclic structure NPGs,we propose a solvent-induced gel formation(SIGF) hypothesis.In this hypothesis,changes in external conditions provide energy to initiate gelation,and the solvent induced the arrangement of gelator molecules via specific induction.Aggregation and precipitation of gelator molecules through the initial structure and the constrained structure provide additional binding to the solvent molecules,thereby forming a gel.This hypothesis comprehensively describes the role of gelator and solvent in gel formation,which can help researchers better understand the formation of NPG.Finally,based on the pharmacological activity of natural products and the material properties of the gel,triterpenoid NPG was constructed as an in local gel drug delivery system for the tumors treatment.By active tracking isolation of Poria cocos and Liquidambar formosana crude extracts with the ability to gel ethanol and water mixed solvent,NPGs 1(poricoic acid A from Poria cocos),14(dehydrotumulosic acid from Poria cocos)and 15(liquidambaric acid from Liquidambar formosana) which are available for use in vivo are obtained.Characterization of the gel properties of 1/NPG,14/NPG and 15/NPG showed that all three NPG are stable gels composed of three-dimensional network fiber structures.2D-NMR-NOESY,UV,IR and 1D-~1H-NMR results showed that the formation of NPG was not only affected by the intermolecular interaction of NPGs but also by the interaction between solvent and NPGs.By examining the self-healing,injectability,anti-inflammatory activity and the in vivo inflammatory properties of the carrier,15/NPG with excellent physical properties,strong anti-inflammatory activity and safe implantation was identified as follow-up drug carrier.The hydrophilic antitumor drug doxorubicin hydrochloride(DOX) as model drug were successfully loaded into 15/NPG(DOX-15/NPG) by incorporation.In vitro and in vivo drug release study showed excellent sustained release effect of Drug-15/NPG,and the in vitro antitumor activity study revealed that the anti-tumor activity of DOX-15/NPG was 3-20 times stronger than that of free drugs.The tumor treatment effect of DOX-15/NPG on the BALB/c mouse bearing 4T tumor showed that the DOX-15/NPG group had the best inhibitory effect on tumors in all treatment groups(The inhibition rate can reach 97.6%).In addition,the tumor-bearing mice treated with DOX-15/NPG also had minimal toxic side effects,improved immune function,better physical health,stronger body recovery function,and longer lifespan.The successful construction of NPG drug delivery system with excellent therapeutic effects provides a path to explore new functions and applications of natural products.