Study On Degradation And Stability Of Sulforaphene

Sulforaphene, extracted from cruciferous plants, is one of the anticancer isothiocyanates. Sulforaphene not only could induce the activity of Ⅱ phase enzyme, but also could inhibit the activity of Ⅰ phase enzyme. The biological activities of sulforaphene, such as anticancer, antioxidant, antibacterial and so on, have been confirmed gradually. The preparation technology of high purity sulforaphene had been stablished in our lab. But sulforaphene degradation still happened even if it was stored in 4℃ or -20℃. This phenomenon brings a lot of negative effects in the applied research of sulforaphene. This thesis focuses on the study of degradation mechanism in order to undertake reasonable efforts to enhance the stability of sulforaphene. The main contents of the thesis are as followings:Firstly, the stability of sulforaphene in aqueous solution was study. The key factors, including light, temperature and pH values, were involved. The results showed that sulforaphene was stable when it was exposed to the light. But the degradation rate was accelerated gradually as the temperature or pH value rose. The thermal degradation of sulforaphene could be described by first-order reaction kinetics in different pH values. Arrhenius equation could describe the degradation of sulforaphene in different pH values. These degradation models could forecast the residual rate of sulforaphene in different solutions at any time very well.Secondly, the thesis focuses on the degradation mechanism study of sulforaphene in aqueous solution. The high purity of degradation products could be purified by preparative chromatography. The structure of the degradation product was analyzed with element analyzer, LC-MS, NMR and infrared analyzer. The analysis results of degradation product demonstated that water content was a vital factor of the sulforaphene storage. The degradation product of sulforaphene during storage was found to be its dimer. This product was formed by the interaction between-N=C=S groups on sulforaphene and -NH2 groups which was formed by nucleophilic attack of the hydroxyl groups in water.Thirdly, the stability and degradation mechanism of sulforaphene in different solvents were studied futher. Sulforaphene was stable in aprotic solvents, such as acetonitrile, dichloromethane, ethyl acetate and acetone. But it was unstable in protic solvents, such as alcohols. The alcohols could accelerate the sulforaphene degradation rate. First, O-thiocarbamates was formed by the reaction between-N=C=S groups on sulforaphene and oxygen atom on alcohols. Second, R-C (=S)-O-R1 could change into R-C (=O)-S-R1 in alcohols, reversibly.Finally, some measures were taken to enhance the stability of sulforaphene. The purpose was to lower the effect of water on sulforaphene. First, sulforaphene microcapsules were prepared by spray-drying using maltodextrin, hydroxypropyl-β-cyclodextrin, chitosan, bovine serum albumin and soy protein as wall materials. The stability of sulforaphene in maltodextrin and hydroxypropyl-P-cyclodextrin microcapsules could be enhanced more than 100% in the thermal test. Second, high purity sulforaphene was stored in vacuum drying oven with phosphoric anhydride in the bottom of the oven. The residual rate of the sulforaphene was up to 97% after 12 months. Third, the storage temperature could be lowered. Experimental results show that the sulforaphene hadn’t degraded when it was stored below -80℃ after 3 months. Fourth, water activity of the samples could be lowered. The residual rate of sulforaphene stored in PEG 400 was 1.2 times of sulforaphene after 5 weeks. Finally, the sulforaphene could be stored in various oils, respectively. The stability of sulforaphene stored in soybean oil could be enhanced by 30%.The above results not only lay foundation for sulforaphene storage and applied research but also could provide guidance for the separation and purification of sulforaphene.