Based On Microwave Assisted DES Extraction Of Forsythiaside A And Activity Research

In 2003,Professor Andrew P.Abbott proposed the concept of Deep Eutectic Solvents(DESs)for the first time.As a new generation of ion liquids,DES may be obtained by mixing hydrogen bond acceptors and hydrogen bond donors at a specific ratio in heating conditions.Due to its low toxicity,good biodegradability and low raw material prices,DESs have been commonly used in catalytic,synthetic,electrochemical,extraction and separation of Traditional Chinese Medicines.Forsythia suspensa(Thunb.)Vahl is a genus of Forsythia suspensa,a medicinal material of Shanxi Province.According to the 2015 Chinese Pharmacopoeia,Forsythia suspensa has medical benefits of clearing heat and detoxification,reducing swelling and dispersing and it is effective when used for the treatment of catarrh,warm disease and so on.Forsythiaside A(FA)is one of the quality markers of Forsythia suspensa.It is recorded in the Chinese Pharmacopoeia that the FA should not be less than 0.25% on a dry basis.FA has anti-inflammatory,antibacterial,anti-oxidative and neuroprotective effects.In this thesis,the author studied that the stability and extraction of FA based on newly synthesized,alcohol-based DESs and evaluated the biological activity of Qingqiao DES extract.The main research results are as follows:1.Investigation of the stability of FA in different solvents.Firstly,the effects of different factors(temperatures,solvent p H,humidity,oxidant and antioxidant)on stability of FA were explored in several solvents,including water,methanol,ethanol and four DESs.From solvent point of view,DESs were better than water and organic solvents in all conditions,and DES-B2(choline chloride: 1,2-Propylene glycol(1:2)),with the best effect that FA content in DES-B2 remained above 75% after heating at 90 °C for 6h while FA completely decomposed in aqueous solution and methanol.We speculated that it is due to that the formation of more intermolecular hydrogen bonds between DESs and FA enhances the intermolecular interaction of FA thereby improving the stability of FA.From the perspective of factors,high temperature,alkaline p H conditions and the oxidant damaged the stability of FA.After the aqueous solution of FA was placed in dark condition with high temperature for 6 h,FA completely decomposed.The alkaline p H condition also accelerated decomposition of FA to disappear after 3 h.After 48 hours the oxidant H2O2 was added in FA solution and kept in room temperature and dark condition,FA content was found only 5.1%,while the antioxidants effectively inhibited the decomposition of FA.Factors affecting the stability factors of FA may be showed in order: high temperature > solvent p H = 9 > the oxidant > high humidity > room temperature > solvent p H = 4 > the antioxidant.2.FA was extracted from Qingqiao in DESs by microwave-assisted method.By comparing the extraction ratio of FA,one of the main components in Qingqiao,DES-B3(Ch Cl-1,2-propanediol 1:3)was selected as the extraction solvent because of the approximated extraction rate.20% water content was optimized and used in the subsequent experiments.The response surface methodology was used to optimize the extraction temperature,extraction time,extraction power and liquid-solid ratio.The results from methodological investigation showed that the optimized extraction conditions were effective and stable.Compared with the heating reflux in the traditional solvent,the method takes a short time with the high efficiency.Scanning electron microscopy was used to observe the microstructure of Qingqiao powder from which FA was extracted by the different extraction methods.It turned out that the sample with microwave-assisted DES extraction suffered the most destructiveness,which may attribute to the high extraction efficiency.3.Evaluation of biological activity of Qingqiao DES extract.The DES solvent displayed almost no cytotoxicity in three cell lines(EC50 > 24000 mg/L);the cell morphologies showed no obvious change after treatment by the DES solvents at the different concentrations.Qingqiao DES-B3 extract and Qingqiao aqueous extract both improved LPS and Aβ-induced inflammation,the former working better.DPPH· radical scavenging activity of Qingqiao DES-B3 extract increased in a dose-dependent manner,with IC50 value of 2370 mg/L,suggesting Qingqiao DES extract has a certain free radical scavenging activity.In conclusion,the stability of FA in different solvents,DESs-based microwave extraction of FA from Qingqiao and the bioactivity of Qingqiao DES extract were investigated in the paper.Compared with other solvents,DESs significantly improved the stability of FA.The extraction time was greatly shorter and the extraction efficiency was increased using optimized DES extraction conditions then the other extraction methods in the traditional solvents.Finally,Qingqiao DES extracts at the different concentrations improved cell viability,reduced the inflammatory and appeared the certain anti-oxidation functions.