Effect Of Ultrasonic Effect On Degradation And Isomerization Of Dicafeylquinic Acid And Its Mechanism

Ultrasound has received a widespread popularity in the utilization of polyphenols and other active components extraction.Nevertheless,relevant literature has justified that the free radical of ultrasonic cavitation can generate a certain impact on the stability of polyphenols,while the unreasonable ultrasonic treatment will set off the degradation of polyphenols.The main active ingredient of chrysanthemum is caffeoylquinic acid which includes the representative component of dicaffeoylquinic acid like 3,5-dicaffeoylquinic acid(3,5-diCQA).Accordingly,it is of great significance to investigate the influence of ultrasound on the degradation and isomerization of dicaffeoylquinic acid and explicit its degradation methods and mechanism so as to strengthen its stability during the process of ultrasonic extraction.This paper designs the degradation kinetic model for 3,5-diCQA,4,5-diCQA and3,4-diCQA and analyzes the degradation products,which contributes to interpret their channels and mechanisms of degradation and isomerization in the process of ultrasonic treatment.Furthermore,it is beneficial for laying a theoretical and technical foundation for figuring out an efficient,environmental-friendly and low-carbon ultrasonic extraction method of Chrysanthemum morifolium.The key analysis and conclusions are as follows:(1)To investigate the impact factors of different ultrasonic solvents on the stability of 3,5-diCQA,4,5-diCQA and 3,4-diCQA.Also to investigate the effects of different ultrasonic parameters(ultrasonic temperature,ultrasonic time,ultrasonic power,ultrasonic pulse duty cycle and ultrasonic liquid level height)on the stability of dicaffeoylquinic acid.Specifically,this study manifested that the degradation of three kinds of dicaffeoylquinic acid was significant under the context of pure water,50% methanol and 50% ethanol.It found that ultrasonic temperature and ultrasonic power have enormous impacts on the stability of 3,5-diCQA;The degradation rate of3,5-diCQA increased first and then decreased with the extension of ultrasonic time and the augment of ultrasonic temperature.In addition,the situation of ultrasonic pulse duty cycle and liquid height also have the certain impact on the stability of3,5-diCQA.Meanwhile,there was a generally increasing tendency of the free radical concentration with the extension of ultrasonic time by measuring the free radical concentration in 3,5-diCQA solution with 50% methanol as solvent under different ultrasonic time.(2)It established different ultrasonic degradation kinetic model by comparing and analyzing the ultrasonic stability of 3,5-diCQA,4,5-diCQA and 3,4-diCQA under different p H environment.Accordingly,this research indicated that the stability of3,5-diCQA,4,5-diCQA and 3,4-diCQA were the most balanced situation under acidic conditions;At the same time,the stability decreased gradually with the increase of p H,which shown that ultrasound promoted its degradation and isomerization.Under alkaline conditions,3,4-diCQA is the least stable material that tended to easily isomerize to 3,5-diCQA;Similarly,three kinds of monocaffeoylquinic acid including3-CQA,4-CQA and 5-CQA were also produced from this experiment.(3)It investigated the impacts of three different concentrations of EGCG and ascorbic acid(AA)(2:1,1:1,0.5:1)on the ultrasonic stability of 3,5-diCQA,4,5-diCQA and 3,4-diCQA at different p H and constructed the degradation kinetic model.As a result,the study manifested that the addition of different concentrations of EGCG and AA generated diverse protective impacts on the ultrasonic degradation of 3,5-diCQA,4,5-diCQA and 3,4-diCQA;While,EGCG has more intensively protective effect than AA,especially when EGCG reaches high concentration ratio;EGCG causes more conspicuous destruction to the stability of 3,5-diCQA,4,5-diCQA and 3,4-diCQA than AA,while neither EGCG nor AA can completely offset the adverse impact caused by ultrasonic effect.