Structure-activity Relationship Study Of Magnolol/Honokiol Derivatives On Cytotoxicity Of Two Fish Species

Magnolol and honokiol are two main active ingredients of traditional Chinese medicine Mangnolia officinalis.Existing studies have shown that these two natural compounds can effectively inhibit fish pathogens such as Grass Carp Reovirus,Ichthyophthirius multifiliis,Aeromonas hydrophila and Saprolegnia,and their chemical structure is simple,easy to synthesize and modify.In the process of transforming and modifying its structure,we need to study the effects of structural changes on fish toxicity.In vitro cultured fish cells is one of the most commonly used methods of toxicology.This study used the principles and techniques of organic chemical synthesis to synthesize magnolol and honokiol derivatives and detect their toxicity to Epithelioma Papulosum Cyprini cells?EPC?and Grass Carp Ovary cells?CO?.The result of cytotoxicity was further evaluated with quantitative structure-activity relationship?QSAR?based on comparative molecular field analysis?CoMFA?.This can explain the quantitative variation between the structure and toxicity of compounds,and speculate on its possible mechanism of action,providing a basis for the subsequent design and synthesis of more toxic compounds,providing references for other new aquatic products too.The results obtained are as follows:1.Synthesis and identification of magnolol/honokiol derivativesA series of reactions,such as alkylation,nitration,hydrogenation reduction,etc.,were carried out by reaction of magnolol and honokiol,column chromatography and spectroscopic identification to synthesize 71 derivatives,which include 29 aromatic amine derivatives,14halogenated derivatives,16 alkyl derivatives and 16 other derivatives.2.Toxicity of magnolol/honokiol derivatives to fish cellsThe EPC cells and CO cells were used as research objects,and the toxicity of 71derivatives to two cells was detected by CCK-8 to gain CC₅₀.According to the results of the cytotoxicity test,it was found that most compounds were similar in the toxicity of EPC cells and CO cells as the concentration increased.Different substituents have a great impact on the toxicity of derivatives:When C-3,C-3'position were substituted by a hydroxyl group or a nitro group,the toxicity of the compound was significantly reduced..After the substitution of the hydroxyl group?C-2,C-2',C-4'position?,most of derivatives increased the toxicity,especially when the magnolol hydroxyl group was formed into a ring,the toxicity was significantly increased.3.Structure-activity relationship of magnolol/honokiol derivatives to fish cytotoxicity29 and 9 derivatives were selected as training set and test set respectively.The most toxic compound 12?2,13-diallyl-6,7,8,9-tetrahydrodibenzo[b,d][1,6]dioxecine?was used as template molecule to establish CoMFA models of two cells.The cross-validation coefficient q² of the EPC cell CoMFA model is 0.536,the optimal number of components n is 4,the r²is 0.987,and the contribution ratio of the stereo field to the electrostatic field is84.1%and 15.9%,respectively.The cross-validation coefficient q² of the CO cell CoMFA model is 0.557,the optimal number of components n is 10,the regression coefficient r² is0.989,and the contribution ratio of the stereo field to the electrostatic field is 87.0%and13.0%,respectively.The fitted graphs of the predicted values and experimental values obtained by the model showed that both models had significant statistical significance,strong stability and good predictive ability.Three-dimensional equipotential maps were established for the two models by partial least squares method,which indicated that when introduced a big group at the C-2,C-9,C-2'and C-9'positions of magnolol and honokiol,a smaller group with a negatively charged group at the C-2,C-2'positions,and a positively charged group at one side of the allylic group?C-9 and C-9'position?may result in increased toxicity.In summary,the results showed that different sizes of negatively charged groups were introduced at the C-2,C-2'positions and different sizes of positively charged groups at C-9,C-9'of magnolol and honokiol could increase toxicity in different degrees.This study provides a basis for the subsequent design and synthesis of more efficient and lower toxicity compounds.