Study On Structure-activity Relationship And Antifungal Mechanism Of Glycyrrhizin With Anti-inflammatory Activity

The legume licorice,also commonly known as "old country",is a more common tonic Chinese herbal medicine.Numerous studies have reported that licorice extracts have anti-inflammatory and anticarcinogenic effects.This topic discussed the structure-activity relationship of glycyrrhizin analogs and glycyrrhetinic acid derivatives,and initially studied their anti-inflammatory mechanism,providing a theoretical basis for the synthesis of compounds with high activity and low toxicity.(1)Firstly to investigate whether the inflammatory inhibitory activities of glycyrrhizin analogs and glycyrrhetin derivatives were related to cell viability,their cytotoxicity were evaluated by MTT assay in RAW264.7 cells.These results indicated that the non-toxic concentrations were further used in subsequent experiment processes.(2)Secondly in order to evaluate the anti-inflammatory effects of glycyrrhizin analogues and glycyrrhetin derivatives and to summarize the structure-activity relationship.These compounds were diluted to the corresponding concentration.RAW264.7 cells were pretreated with compounds for 1 h,in the presence or absence of LPS(1 μg/mL)for 24 h,and then the cell supernatant was extracted.Griess reagent and ELISA reagent were used to detect the level of lipopolysaccharide(LPS)-induced NO,IL-6,TNF-α release in RAW264.7 cells.Glycyrrhizin analogues:(i)the anti-inflammatory activity of 18α-epimer of the oleanane-type aglycone was superior to that of 18β-epimer;(ii)the number of glucuronic acid at the C-3 position had effect on the anti-inflammatory activity(mono-glucuronide > zero-glucuronide > bis-glucuronide.Glycyrrhetin derivatives:(i)compound 5 with α,β-unsaturated carbonyl moiety >glycyrrhetic acid;(ii)heterocycle amide > linear alkyl amide > branched alkyl amide;(iii)amide > ester.Compounds 6k and 6l with piperazine moiety exhibited the most potent nitric oxide(NO)and interleukin-6(IL-6)inhibitory activity.(3)Finally to further investigate the anti-inflammatory mechanisms of glycyrrhizin analogues and glycyrrhetin derivatives,we selected compounds18α-GAMG and 6k with better anti-inflammatory activity respectively.Western blotting and immunofluorescence showed that compounds 18α-GAMG and 6k reduced decreased the expression of i NOS,COX-2,as well as inhibits LPS-induced NF-κB and MAPK activation in RAW264.7 cells.