Synthesis And Systemicity Of Phenazine-1-carboxylic Acid-amino Acid Conjugates In Caster Bean

Shenqinbactin?Phenazine-1-carboxylic acid,PCA?is an N-containing heterocyclic biopesticide mainly used for controlling rice sheath blight caused by Rhizoctonia solani.In addition,PCA is known as a broad-spectrum fungicide which has been proven effective against various plant diseases,such as rice blast,wheat head scab,and gray mold.It has been registered as a biofungicide"Shenqinbactin"in China.Shenqinbactin owns high bioactivity but poor systemicity.In this research,in order to improve the systemicity of PCA,taking PCA as a lead compound,a series of phenazine-1-carboxylic acid-amino acids conjugates were synthesized via simple chemical synthesis,and the systemicity regularity and mechanisms of these conjugates are also discussed.In this research,16 PCA-amino acid conjugates?11 PCA-L-amino acid conjugates,5 PCA-D-amino acid conjugates?were synthesized.The in vitro fungicidal activity test showed that all conjugates exhibited certain fungicidal activities against 6phytopathogenic fungi.The fungicidal activities of conjugate D-4d against Altemaria solani,conjugate D-4c against Magnaporthe oryzae and conjugate D-4g against both A.solani and M.oryzae were all higher than that of the control PCA.The EC₅₀ values of them were 0.064±0.003 mmol/L,0.076±0.006 mmol/L,0.066±0.006 mmol/L and0.056±0.002 mmol/L respectively.Overall,D-configuration amino acids retain higher fungicidal activity.The results of the systemicity test of 16 PCA-amino acid conjugates showed that introducing an amino acid to PCA could endow PCA with phloem mobility,and the systemic rules of these 16 conjugates were not completely consistent with the Kleier model.Among the L-configuration amino acid conjugates,PCA-L-Val exhibited the highest phloem mobility,with the concentration detected in the phloem sap of 23.94±2.84?mol/L,and PCA-L-Ala exhibited the highest xylem mobility with the concentration of 26.07±0.54?mol/L.There is no direct relationship between the phloem mobility and xylem mobility of these compounds.By comparing the systemicity of the L-amino acid conjugates and D-amino acid conjugates,it indicated that the phloem mobility of the L-amino acid conjugates is usually higher than D-amino acid conjugates.In contrast,the xylem mobility of the D-amino acid conjugates is higher than L-amino acid conjugates.It is indicated that the type of amino acid,as well as the configuration of the amino acid can affect the systemicity of the conjugates.In summary,several PCA-amino acid conjugates still retain a high bioactivity.In addition,introducing an amino acid to PCA could endow PCA with phloem mobility in caster bean and enhance the xylem mobility of the parent molecule.The process of systemicity of PCA-amino acid conjugates in caster bean may involve not only passive diffusion,but also active transport mediated by carrier,whereas the corresponding carrier of the L-amino acid and the D-amino acid is not clear now,which needs to be further studied.