| 5% to 8% of the global population suffer from autoimmune diseases,and clinical treatment drugs have poor specificity,large toxic side effects,and high prices.poor disease specificity,large toxic,side effects and high prices.Natural products have the advantages of rich sources and low side effects,and have received extensive attention from researchers in recent years.Astilbin is a natural dihydroflavonol glycoside compound isolated from Smilax glabra.It has significant immunosuppressive,anti-oxidant,anti-cancer,anti-diabetic and other pharmacological activities.Astilbin can selectively inhibit activated T cells without affecting normal T cells and humoral immunity.It is more selective and less toxic than clinical drugs for the treatment of autoimmune diseases.As the dominant backbone of the structure of flavonoids and astilbin,5,7-dihydroxychromone also has a variety of pharmacological activities such as anti-inflammatory and immunosuppressive activities.The bioavailability of astilbin is only 0.066%,which greatly limits its clinical application;at the same time,the research on the structure-activity relationship is insufficient,which leads to the lag in the development of this variety.In this paper,astilbin and its dominant backbone,5,7-dihydroxychromone,are used as lead compounds to modify the chemical structure.Based on the principle of prodrugs,its derivatives are designed and synthesized to improve water solubility,improve its pharmacokinetic properties,and increase oral administration.Bioavailability: Through biological activity evaluation and computer virtual docking,the structure-activity relationship of astilbin is studied to provide a basis for screening clinical drug candidates with good druggability.(1)Chemical synthesisIn this paper,two methods of semi-synthesis and total synthesis are used to introduce glycosyl fragments into the astilbin core and fully synthesize the dominant backbone of astilbin 5,7-dihydroxychromone and modify it by glycosylation.Using a semi-synthetic method,with astilbin as the starting material,under the action of acetic anhydride and DMAP,fully acetylated astilbin(AB-I-1)was obtained with a yield of 73.8%;according to the astilbin core The reactivity of the upper hydroxyl group is different,and the protective group is selectively removed to obtain the fully acetylated astilbin C-7 hydroxyl derivative(AB-I-2)with a yield of 73.8%;AB-I-2 and Bz-Br-GL,Bz-Br-GA,Bz-Br-AB,Bz-Br-MA and other glycosyl donors,the glycosylation reaction was carried out under the condition of silver carbonate as a catalyst,and the C-7 glycosylation product was synthesized :AB-Ⅰ-3-GL,yield57.1%;AB-Ⅰ-3-GA,yield 60.3%;AB-Ⅰ-3-AB,yield 52.5%;AB-Ⅰ-3-MA,yield 59.7%.The above-mentioned glycosylation product was deprotected under potassium tert-butoxide-methanol conditions to synthesize astilbin C-7 glucoside derivative AB-I-4-GL with a yield of 52.1%;astilbin C-7 galactose Glycoside derivative AB-Ⅰ-4-GA,yield 41.8%;Astilbin C-7 arabinoside derivative AB-I-4-AB,yield59.8%;Astilbin C-7 mannoside derivative Compound AB-I-4-MA,the yield is47.2%.Using a total synthesis method,starting with 2,4,6-trihydroxyacetophenone,2,4,6-trichloro-1,3,5-triazine(TCT)and boron trifluoride ether solution Under the action,a 5,7-dihydroxychromone skeleton(CM-1)is obtained;benzyl bromide is selected to protect the C-5 and C-7 hydroxyl groups under the conditions of potassium carbonate/potassium iodide to obtain 5,7-dibenzyloxy Chromone skeleton(CM-2),the two-step yield is 35.5%;iodobenzenediacetic acid oxidizes the double bond to obtain the hydroxychromone skeleton at the C-3 position,5,7-dibenzyloxy-3-hydroxychromone(CM-3),the yield is 68.29%;the C-3 hydroxyl group and the Bz-Br-Rh glycosyl donor are glycosylated under the condition of silver trifluoromethanesulfonate to obtain the key intermediate of the C-3 rhamnoside5,7-dibenzyloxy-3-O-rhamnose chromone(CM-4),the yield was 18.9%,and then the target compounds CM-5’ and CM-7 were synthesized respectively.After removing all the protective groups of CM-4 under the potassium tert-butoxide-methanol system,5,7-dihydroxy-3-O-rhamnose chromone(CM-5’)was obtained,and the yield was 25.5%.First remove the phenolic hydroxyl protecting group of CM-4,and then selectively perform glycosylation reaction with the Bz-TCA-Rh glycosyl donor at the C-7 position to obtain 5-hydroxy-3,7-O-diperbenzyl Acylation protects the rhamnose chromone derivative(CM-6)with a yield of 38.1%;finally,all the protective groups are removed in the potassium tert-butoxide-methanol system to obtain5-hydroxy-3,7-O-diones Plumose chromone derivative(CM-7),the yield was 54.9%.(2)Pharmacological experimentIn this paper,a mouse model of delayed hypersensitivity is used to measure the ear swelling rate,thymus index,spleen weight index,and the contents of MMP-2,MMP-9,TNF-α,and IL-10 in mouse plasma.The index evaluates the immunosuppressive activity of astilbin derivatives;finally,the mechanism of astilbin and its derivatives is verified from the molecular level by computer virtual docking with human MMP-2 and MMP-9 proteins.AB-I-4-GL,CM-5’,and CM-7 can significantly reduce the level of ear swelling rate,MMP content,TNF-α content and increase IL-10 expression after sensitization.AB-Ⅰ-4-GL,CM-5’,CM-7 ear swelling rate inhibition effect is better than astilbin group,combined with the water solubility test results,the pharmacological activity of astilbin derivatives may increase with the increase in water solubility,leading to it The increase in bioavailability is related,but slightly worse than that of the dexamethasone group.From the results of spleen weight index and thymus index,compared with the dexamethasone group,astilbin derivatives have lower toxicity and are suitable for long-term use.(3)Research on the structure-activity relationship(1)Modification of the glucosyl fragment of astilbin nucleus can improve water solubility and pharmacological activity.From the molecular level,it may be related to the increase of IL-10 level and the increase of MMP-9 inhibitory effect;(2)CM-1does not have immunosuppression Activity,CM-5’ activity is better than astilbin,indicating that the presence of rhamnosyl fragments is very important for immunosuppressive activity;(3)Removal of the B ring can improve water solubility and pharmacological activity.From a molecular level,it may be related to TNF-The decrease of α content is related;(4)The pharmacological activity of CM-7 is slightly worse than that of CM-5’,but the spleen weight index is slightly higher,and the toxicity is relatively small;from the molecular level,it may be related to the increase of IL-10 level and the inhibitory effect of MMP-2 The improvement is related. |
