Studies On Antimicrobial And Antioxidant Characteristics Of Wood Vinegars And Its Phenolic Acid Extracts Obtained From Eucommia Ulmoides Olivers Branches

In this study,wood vinegars at different pyrolysis temperatures were prepared by slow pyrolysis of Eucommia ulmoides Olivers branches.Samples of pyrolysis extract were collected every 30℃from 90℃to 510℃,and the whole pyrolysis samples were collected from 90℃to 510℃.After the collected pyrolysis extract can stand at low temperature and protected from light,a clarified wood vinegar sample is obtained by siphon method.The samples were labeled from WV_90¹20 to WV_480⁵10 and WV_90⁵10,respectively,according to the preparation temperature.The physical and chemical properties and chemical composition of the wood vinegars were determined.The agar plate diffusion method was used to study the antimicrobial effect of wood vinegar WV_90¹20 to WV_480⁵10 on bacteria,fungi and plant pathogens.The acid and phenolic substances in the wood vinegar WV_90⁵10 were extracted by extraction method,and the extraction process parameters were optimized.The inhibitory effect on bacteria and antioxidant properties of acid extracts and phenolic extracts were studied.The chemical constituents and antibacterial properties of wood vinegar in different pyrolysis temperature sections were studied.The results showed that with the increase of pyrolysis temperature,the yield of wood vinegar increased first and then decreased,and the yield of WV_300³30 sample was the largest,accounting for 23.26%of the total crude wood vinegar,and the lowest pH 2.39 and the highest total acid content 12.70%were found in the WV_270³00 sample.The highest content of organic components in wood vinegar is phenols,followed by ketones,benzenes,aldehydes,alcohols and organic acids.Except for the relative content of benzenes and aldehydes first rises and then decreases,there is no obvious regularity between the content of the other four organic components with the pyrolysis temperature.Wood vinegar has the best inhibitory effect on bacteria,followed by plant pathogens,which has a poor inhibitory effect on fungi.The WV_240²7040²70 sample has outstanding antibacterial activity against Staphylococcus aureus and Bacillus cereus,showing a certain unique bacteriostatic effect.while WV_300³30 sample is excellent for three bacteria,two fungi and four plant pathogenic bacteria,which showed extensive antimicrobial activity.The optimization of the extraction parameters of organic acid in wood vinegar were studied.It was found that the P value of the quadratic regression model was less than 0.001,the difference was extremely significant.Within the horizontal range of each factor,the factors affecting the organic acid content of organic acid extracts in wood vinegar were:NaHCO₃ solution extraction times>NaHCO₃ solution concentration>NaHCO₃ solution volume ratio.The optimum extraction process parameters of organic acid in wood vinegar were as follows:the concentration of NaHCO₃ solution was 4.12%,the volume ratio of NaHCO₃ solution was 1.29,and the number of extractions of NaHCO₃ solution was 2 times.The verification experiment results show that the relative deviation between the measured value and the predicted value is only 0.57%,which is in good agreement,and further verifies the reliability of the regression model.To study the antioxidative properties of phenolic extracts from wood vinegar,it was found that the total phenol content was:5.00%.KOH solution>1.75%Ba（OH）₂ solution>6.00%NaOH solution.The phenolic extracts and wood vinegar can scavenge three kinds of free radicals:ABTS free radicals>DPPH free radicals>hydroxyl radicals.The phenolic extract obtained from the 1.75%Ba（OH）₂ solution has the same ability to scavenge ABTS radicals as ascorbic acid,while the wood vinegar has a much better ability to scavenge ABTS free radicals than ascorbic acid and exhibits superior antioxidant capacity.Studying the antibacterial properties of wood vinegar and its acid extracts and phenolic extracts,the results showed that the phenolic extract had the worst bacteriostatic effect,followed by acid extracts;wood vinegar against Bacillus subtilis,Escherichia coli,and Staphylococcus aureus are more bacteriostatic than minocycline,while their effect on Azotobacterial and Proteus is weaker than minocycline.Therefore,the bacteriostatic properties of wood vinegar are not determined by a specific component,but by the interaction of many different organic components.