Modeling of acid hydrolysis of solasodine glycosides. Part III: Combined glycoside hydrolysis and solasodiene formation—guidelines for commercial hydrolysis

Abstract

Kinetic models for glycoside hydrolysis and solasodiene formation are combined, P. G. CRABBE and COLIN FRYERand using previous experimental data the effect of changes in reaction conditions on hydrolysis times and the proportion of solasodiene in the final hydrolysed product are established. These are used to give a set of guidelines for commercial hydrolysis. The use of the models: for new commercial situations is explained. SCOPEMathematical models have been proposed to describe the hydrolysis of pure a-solasonine and a-solamargine (Part I), and the further reaction of pure solasodine to produce solasodiene (Part 11). The proposed models have been shown to describe adequately these three independent reactions. Methods have been presented for determination of the model parameters from experimental data. Any commercial hydrolysis will be more complex, involving all of these three reactions. The individual kinetic models need to be combined to describe such systems. The description of the hydrolysis reaction must be extended to incorporate solasodiene formation from the released solasodine so that the time for hydrolysis and the proportion of solasodiene in the final product can be predicted. Consideration of the predictions of this combined model, using parameter values obtained in the studies of the individual reactions, should provide guidance on the optimization of the hydrolysis process. CONCLUSIONS AND SIGNIFICANCEPrevious models are easily extended to more complex hydrolysis situations; a model is established for the most general hydrolysis system, that of the hydrolysis of a mixed glycoside substrate with allowance for solasodiene formation from the released solasodine. Using the experimental rate data for a-solasonine hydrolysis (from Part I) and that for the solasodine to solasodiene conversion (from Part II), estimates of the reaction times (for specified conversions) and of solasodiene percentages in the final product have been obtained. For the conditions studied, solasodiene percentages in the final product are low (generally less than 1Y0k the problem of solasodiene formation is not as great as previously reported, provided that the reaction is stopped once hydrolysis is complete. Reaction rates increase with acid concentration and temperature, but decrease sharply with the addition of water to an alcohol solvent. The glycoside concentration has no effect unless solubility limits of the intermediates are exceeded. = initial concentration LITERATURE CITED Crabbe, P. G., and C. Fryer, "Rapid quantitative analysis of solasodine, solasodine glycosides and solasodiene by high pressure liquid chromatography," J . Chromtogr., 187, p. 87 (1980). Tourky, A. R., A. A. Abdel-Hamid, and I. Z. Slim, "Acidity in mixed solvents: 11. Hammett's acidity function in isopropanol-and ethylene glycol-water mixtures,

Rapid screening of toxic glycoalkaloids and micronutrients in edible nightshades ( Solanum spp.)

“…For quantification of total alkaloid aglycone, the sample was prepared based on protocols by P.G. Crabbe [ 10 ] with modification. Briefly, around 400 mg of sample was accurately weighed and hydrolyzed by 20 mL 0.5 M anhydrous methanolic hydrochloric acid in an eight dram vial with a screw cap, and incubated in a 70 °C water bath for 120 min.…”