Study On The Synthesis And Properties Of D-isoascorbyl Esters

Six D-isoascorbyl saturated fatty acid esters (D-isoascorbyl caprylate, D-isoascorbyl caprate, D-isoascorbyl laurate, D-isoascorbyl myristate, D-isoascorbyl palmitate and D-isoascorbyl stearate) were synthesized with lipase Lipozyme435as catalyst by direct esterification and transesterification, respectively. Four D-isoascorbyl mixed-fatty acid esters were synthesized with lipase Lipozyme435as catalyst by the transesterification of D-isoascorbic acid with camellia oil, lard, sesame oil and canola oil, respectively. Six n-alkyl-6-D-isoascorbyl fumarates were synthesized by the reaction of D-isoascorbic acid with mono-n-alkyl esters of fumaric acid chloride which from the the alcoholysis of maleic anhydride with C1-C8n-alkyl alcohol, followed by the isomerization in the present of aluminium trichloride to obtain mono-n-alkyl fumarate, and chlorization with thionyl chloride. All the products were confirmed by1HNMR,13C NMR, FT-IR and ESI-MS.The synthesis reactions were optimized by single-factor experiment with the synthesis of D-isoascorbyl laurate and the synthesis of D-isoascorbyl camellia oil fatty acid esters, respectively. Under the optimized conditions, the yield of D-isoascorbyl laurate was68.2%, and the yield of D-isoascorbyl camellia oil fatty acid esters was48.0%.The alcoholysis and isomerization of maleic anhydride were optimized by orthogonal experiment. The total yield of alcoholysis and isomerization was79.2%-87.3%under the optimized conditions. The yield of n-alkyl-6-D-isoascorbyl fumarates was17.4%-73.2%based on the mono-n-alkyl esters of fumaric acid chloride.The antioxidation activities of D-isoascorbyl mixed-fatty acid esters applied in fresh camellia oil and lard were evaluated by peroxide value (POV) determination, and the antioxidation activities of D-isoascorbyl mixed-fatty acid esters and n-alkyl-6-D-isoascorbyl fumarates were evaluated by scavenging DPPH free-radical activity. The POV data and the scavenging activity data showed that both D-isoascorbyl mixed-fatty acid esters and n-alkyl-6-D-isoascorbyl fumarates had significant antioxidation activity, as compared with commonly oil-soluble antioxidant such as TBHQ, ascorbyl palmitate and D-isoascorbyl palmitate.The anti-microbial activity of mono-n-alkyl fumarates and n-alkyl-6-D-isoascorbyl fumarates was investigated by peptide-agarose diffusion assay. The results showed that both mono-n-alkyl fumarates and n-alkyl-6-D-isoascorbyl fumarates exhibited certain anti-microbial activity against Staphyloccocus aureus, Escherichia coli, Bacillus subtilis and Streptomyces microflavus,as compared with D-isoascorbyl acid, sodium benzoate and potassium sorbate.