Study On Preparation And Properties Of Salts Of Oleanolic Acid And Ursolic Acid

Oleanolic acid and ursolic acid have many pharmacological effects,such as anti-cancer,liver protection,anti-diabetes,anti-inflammatory,etc.So they have broad application prospects.However,their water solubility and bioavailability are very poor,which greatly limits their clinical application.Therefore,it is necessary to increase the solubility of oleanolic acid and ursolic acid.In this paper,choline,tetraethylammonium,1-ethyl-3-methylimidazole,cetylpyridine,1-（2-hydroxyethyl）-3-methylimidazole,1-octyl-3-methylimidazole and Trihexyl tetradecyl phosphine were selected as counterions to react with oleanolic acid and ursolic acid.Fourier transform infrared spectroscopy（FTIR）,nuclear magnetic resonance（¹H NMR）and thermogravimetric analysis（TGA）proved that salt formation occurred,and the purity and thermal stability of the synthesized salts were very good.Finally,the solubility of all synthetic salts in water,simulated gastric fluid（SGF）and simulated intestinal fluid（SIF）was determined.The results showed that the prepared salts achieved the purpose of improving the solubility of oleanolic acid and ursolic acid.Supramolecular hydrogels have many excellent properties,such as good biocompatibility,excellent swelling and permeability,and drug-carrying maintain activity,easy degradation,etc.,so as to be widely used in drug delivery,tissue engineering and other fields.Although there have been some reports about oleanolic acid and ursolic acid gel,there have been no reports on supramolecular hydrogels that salts of oleanolic acid and ursolic acid as gelling factors.Therefore,the preparation of oleanolic acid salts and ursolic acid salts into supramolecular hydrogels is of great significance.In this paper,eight temperature-sensitive supramolecular hydrogels were prepared.The gelling factors were oleanolic acid choline,oleanolic acid tetraethylammonium,and oleanolic acid 1-ethyl-3-methylim--idazole,oleanolic acid 1-（2-hydroxyethyl）-3-methylimi--dazole,ursolic acid choline,ursolic acid tetraethylammonium,ursolic acid 1-ethyl-3-methylimidazole and ursolic1-（2-hydroxyethyl）-3-methylimidazole.The minimum gel formation concentration（MGC）and gel-sol transition temperature(T_gel)of the gel were determined by the“stable to inversion of the test-tube”method.FTIR confirmed that the driving force for gel formation was hydrogen bonding,and field emission scanning electron microscopy（FESEM）and atomic force microscopy（AFM）verified that the gel had a three-dimensional network structure.Finally,rheological studies show that the prepared products are viscoelastic soft solids with good stability.FTIR confirmed that the driving force for gel formation is hydrogen bonding,and field emission scanning electron microscopy（FESEM）and atomic force microscopy（AFM）confirmed that the gels have three-dimensional network structures.Rheological studies showed that the prepared gels are viscoelastic soft solids with good stability.Finally,the tolerance of the prepared gels to strong acid and strong base was investigated.The results showed that they could withstand strong acid and strong alkali and had good application prospects.