| Five new benzopyran carboxylic acid containing fluorine were synthesized from cheap, easily available aromatic aldehyde and trifluoroacetyl ethyl acetate by simple synthetic route. The inhibition effect on Tobacco Mosaic Virus(TMV) was studied through the Necrotic lesions test and the optimal agent was screened out. The resistant mechanism of the optimal agent to TMV was preliminary studied by testing related defense of chlorophyll and related enzyme activities in tobacco infected by TMV to provide evidence for the development of new, effective antiviral agents. Results are as follows:1. Synthesis of novel benzopyran acids containing fluorine:Five new benzopyran esters was obtained from the reaction of salicylaldehyde and trifluoroacetyl ethyl acetate in the presence of piperidine with the yield of 80.2% - 85.8%. Then 5 benzopyran carboxylic acid containing trifluoine were achieved in the yield of 90.3% - 95.7% after the esters were further hydrolyzed, neutralized and isolated in the alcohol solution of alkali. The structures are confirmed by UV, IR, 1H NMR and 13C NMR. The method has such advantages as short reaction time, easy controlled temperature, simple operation and less pollution, etc.2. The induction resistance of benzopyran acids on TMV:The optimal agent was screened by the resistant test of 5 carboxylic acid compounds on Nicotiana glutinosa as the materials using the whole leaf method. The results are as follows: On the whole, the preventive effect of various agents is better than curative effect. Preventive effect: (2e)> (2d)> (2b)> (2c)> (2a)., The rate of prevention and curation of the inhibition rates were respectively 51.60% and 44.41% when the concentration of optimal agent is 300μg/mL, which are higher by 8.30% and 1.11% compared with commercially available antiviral agents benzothiadiazole (BTH). Secondly, the disease index on tobacco NC89 experiment showed: (2e)> (2b)> (2d)> (2c)> (2a). In the disease index and the inhibition effect of prevention trials, 2e is the best agent. The rest are the same basically on the pharmaceutical results besides 2b and 2d.3. The biochemical mechanism analysis of preventive enzymes:After the treatment by optimal agent (2e) (300μg/mL) (T2), the peroxidase (POD) activity peak of tobacco leaves reached earlier by two days compared with the benzothiadiazole (BTH 100μg/mL, T3) control, and the activity peak is higher more 0.82U/mg.min than BTH. This may be due to the cause of oxidation of phenolic compounds and the production of lignin faster after application of the best agents to the inoculated tabacco and then rise to peak ahead of POD activity. Tobacco leaves phenylalanine ammonia-lyase (PAL) activity reach to the peak on the 9th day after application of the best agents to the inoculated tabacco, which is the same as BTH and higher than the highest peak of BTH by 22.56 activity units. The reason may be that gene expression increase controlling the PAL and that promoted a large number of PAL-catalyzed synthesis of metabolites after being stimulated on the body with the agent, which can resist the invasion and the proliferation of TMV. The polyphenol oxidase (PPO) activity of tobacco leaves is very low in the first day after being applied the best agent to the inoculaed tobacco. The activity was significantly increased and higher than any other treatment from the 2th. Compared with BTH, the activity peak appeared at the same day on the 5th, and the maximum activity peak is higher by 97.88 units than BTH. The catalase (CAT) activity got to peak value (87.27) on the first day after the tobacco leaves was treated by optimal agent then being inoculated (T2). The CAT activity of other treatments reaches to peak on the 5th day. The superoxide dismutase (SOD) activity peak of tobacco treated with optimal agent after inoculating occurs later by two days than BTH, and the activity peak is higher by 3.64 units. |
PDF Full Text Request