Zeolitic Imidazolate Framework-8 For Selective Extraction Of Active Components From Caragana Jubata

The medicinal compositions or active components in medicinal plants are one of the major sources to find new drugs or lead compounds.Exploring novel sorbents with good selectivity for extraction and separation of targeted medicinal compositions or active components from complex medicinal plants is interesting and challenging.Metal-Organic Frameworks?MOFs?showed a great potential in adsorption and extraction recently.Herein,we report our primary attempt of zeolitic imidazolate framework-8?ZIF-8?as a model MOF for selective extraction of an active component named 3,4-dihydroxy-8,9-methylenedioxypterocarpan?compound 1?from the dichloromethane?DCM?extract of Caragana jubata?C.jubata?.The plant has a long officinal history in Tibetan medicine,and mainly distribute in Qinghai-Tibet plateau of China.The red heartwoods of the rhizomes of the plant are used as Tibetan medicine,named‘Zuo Mu Xing'.The extraction experiment showed that the enrichment factor of ZIF-8 to compound 1 reached to 57.7 and the recoveries at three spiked levels(50,100,150 mg?L^-1)in DCM extract of C.jubata were 62.1%,66.4%and 75.4%,respectively,with the relative standard deviations less than 2.9%.To explore the relationship between the chemical structure features of adsorbate and the selectivity of ZIF-8,eight main components of DCM extract were isolated by chromatographic methods?silica-gel,Sephadex LH-20,and ODS preparative HPLC and MPLC?,and identified by spectral analysis?NMR,MS,etc.?,including maackiain,?8S?-2,4-dihydroxy-8-hydroxymethyl-4?-methoxydeoxybenzoin,7-hydroxy-4?-meth-oxyisoflavone,5,2?,4?-trihydroxy-7-methoxyisoflavone,3-hydroxy-4,9-dimethoxy-pterocarpan,medicarpin,7,4?-dihydroxyflavanonol and 7,3?-dihydroxy-4?-methoxy-isoflavone.The results showed that the ortho-diphenolic hydroxyls of compound 1were relavent to the selective sorption of ZIF-8.To reveal the adsorption mechanism of ZIF-8 to compound 1,single crystal X-ray diffraction,X-ray photoelectron spectroscopy and the adsorption experiments of ZIF-8 to phenol and catechol were conducted.The results indicated that the selective adsorption occurred on the surface of ZIF-8,and two hydrogen bonds formed between two nitrogen atoms on one ligand of ZIF-8 and ortho-diphenolic hydroxyls on compound 1,which played the dominant roles on the adsorption.The obtained compound 1 showed highly antioxidant activity.The IC₅₀ values for DPPH radical scavenging activities and inhibitory effects on lipid peroxidation were 5.438±0.068?g?mL^-1 and 20.970±0.083?g?mL^-1,respectively,which were better than the positive controls,Vitamin C and BHT.The evaluation of antiplatelet aggregation activities in vitro showed that compound 1 had good antiplatelet aggregation activity,and the IC₅₀ values for inducers ADP and AA were 8.05?M and10.36?M,respectively.In conclusion,this research work initially reveals the potential of MOFs for selective extraction of active compounds from medicinal plants.The innovation of this work lies in:?1?presented the first example of MOFs in selective extraction of medicinal compositions or active components from complex medicinal plants;?2?expended MOFs as novel sorbents in medicinal plants extraction and separation;?3?revealed the feasibility of MOFs for directly selective extraction of trace active compounds out from medicinal plants.The current work may open a new way of MOFs in selective extraction of pharmacological active components from medicinal plants.