The Researches Of Isothiocyanates(ITCs)-bioactive Components In Chinese Horseradish

Organic isothiocyanates (ITCs), the hydrolytic products of glucosinolates in the Cruciferous plants, are the flavor components with pungent taste. Allyl isothiocyanates (AITC) is the dominating ITCs existed in horseradish and wasabia. ITCs show high biological activities and can prevent from DNA-damage and cancer, and inhibit the platelet aggregation, the growth of food spoilage and pathogenic bacteria.The researches about AITC in this thesis included four aspects:(1) The researches about ITCs chemical property: The stability of ITCs in solution had been investigated. The results indicated that the hydrolytic rate increased with the rising of temperature; ITCs were stable in acetone and the hydrolytic rate was very high by ultrasonic wave. In addition, the mechanism of the hydrolyzation was discussed.The UV-spectra of AITC and its thioureas, and kinetic properties of piperidine, morpholine and diethyl amine reacted with AITC were investigated. The studies of kinetics showed thatt the reaction is second-order by spectrometric method. The rate constants and activation energy were determined and the mechanism of the reactions was discussed.The reaction of AITC with hydroxyl/water andβ-cyclodextrin(β-CD) in alkaline media had been investigated by ultraviolet spectrometry. The kinetic parameters of the reaction were measured. It was found that after AITC translating into thiourea, the absorption peak shifted to 226 nm from 240 nm and the molar absorptivity increased about 16 times. The reaction can be seen as a pseudo first-order reaction because the concentration of hydroxyl was constant in the reaction.β-CD can inhibit the reaction of AITC with hydroxyl/water i.e. the hydrolysis of AITC.(2) Methods for ITCs determination: a new method for quantitative determination of the isothiocyanates in horseradish, mustard and the related products has been reported. The isothiocyanates reacted with diethyl amine in acetone media to form the corresponding monosubstitited thioureas. The excess of diethyl amine is back titrated using a standard hydrochloric acid solution and the amount of the isothiocyanates is calculated from the titration values. A spectrophotometric method for ITCs determination in Horseradish, Mustard jam has also been developed. Compared with those of piperidine and morpholine methods, the results indicated that the proposed methods are accurate and convenient.(3) Molecular microcapsules ?of ?cyclodextrin including ITCs: Complexation reactions of AITC withβ-CD and its three derivatives were investigated using spectrophotometry with methyl orange (MO) as a molecular probe. CDs and AITC can form 1:1 complexes. The affinity between HP-β-CD and AITC was the strongest. The association constants of CDs with AITC (K) decreased with the increasing of temperature and increased with the increasing ionic strength. The thermodynamic measurements showed that the inclusive process was enthalpic favour.The molecular microcapsule of AITC inβ-CD was prepared by suspension method. The effect of temperature, time and solvent are studied. The content of AITC in the microcapsules was 43.8 mg/g under optimal conditions and their stabilities were obviously improved because of Van der Waals forces and the steric hindrance. The included isothiocyanates is characterized by infrared spectrometry.(4) Recovery of ITCs from aqueous solutions using macroporous: Static equilibrium adsorption studies were used for comparing the adsorption capacities of the nine resins. The results showed that H103 resin had the best adsorption capacity because of its large and nonpolar surface areas. The effects of pH, temperature and salt concentration on the adsorption capacity of H103 were investigated. The mass transfer zone motion model was used for analyzing the fixed bed adsorption. The length of mass transfer zone of H103 was calculated under definite condition. The effects of the initial concentration of AITC, flow velocity and cross section of the resin column to the length of mass transfer zone have also been investigated.