Synthesis And Antioxidant Activity Of Inositol Triphosphate Carboxylate

The liposouble inositol trisphosphate carboxylates were synthesized from sodium phytate.The optimum conditions for the synthesis of inositol trisphosphate carboxylate were explored.The target products were characterized by IR,LC-MS.The antioxidant activity tests of the target compounds were also investigated.ⅠThe Preparation of inositol trisphosphate and its ammonium saltWhen the hydrolysis degree of phytic acid is about 50%by phytase under 50℃,pH 5.1,the hydrolysate was pumped into a column containing 717 strong anion-exchange resin,then delivered a linear gradient of 0.05-0.7 M HCl.The solution contenting 1,2,6-inostitol trisphosphate were collected,and then saturated Ca（OH）₂ solution was added.The calcium salt was turn into 1,2,6-inostitol trisphosphate through 732 strong anion-exchange resin.The eluent was neutralized by triethylamine and rotary evaporated at 40℃.ⅡEsterification catalyzed by DMAP-DCCThe following esters,1,2,6-inostitol trisphosphate-3,4,5-triacetate（a）,1,2,6-inostitol trisphosphate-3,4,5-tripropionate（b）,1,2,6-inostitol trisphosphate-3,4,5-tripalmiate（c）, 1,2,6-inostitol trisphosphate-3,4,5-tristearate（d）,were prepared from their correspounding carboxylic acid after 48 h,catalyzed by DMAP-DCC in dichloromethane at 30℃. Spectroscopic property and synthetic conditions were analyzed and discussed.ⅢEsterification catalyzed by lipaseThe following esters,1,2,6-inostitol trisphosphate acetate（e）,1,2,6-inostitol trisphosphate palmiate（f）,1,2,6-inostitol trisphosphate stearate（g）,were prepared from their correspounding carboxylic acid catalyzed by lipase.The effect of organic medium, the initial water activity and acyl donor on esterification has been investigated.The results showed that:when carboxylic acid catalyzed by Novozym435 in dichloromethane, the initial water activity 0.175,for 24h in reflux at 40℃,the target compounds were obtained.ⅣThe antioxidant activity testThe antioxidant activities of compounds were tested at concentration of 200,400, 600 mg/kg in rapeseed oil through Schaal experiments at 60℃.Peroxide values（PV） and anisidine values（AV） during storage were measured,in comparison with dibutyl hydroxyl toluene（BHT）.The shelf lives of samples containing antioxidant were forecasted.Results showed that:（1） Target compounds were effective at 400mg/kg as well as BHT on inhibition on lipid peroxidation.（2）1,2,6-inositol triphosphate carboxylate were more effective than 1,2,6-inositol triphosphate-3,4,5-tricarboxylate at experimental concentrations.（3） The shelf lives of oils containing these antioxidants could be prolonged.To assess the effect of the target compounds a,d,e,g on the oxidative stability of the oil in the presence of ferric ions,a similar set of the above samples were prepared with the addition of 0.5 or 1 mg/kg ferric ions.Results showed:compounds a,d,e,g were more effective than BHT in the presence of ferric ions.