印楝素水解动力学研究及水解产物结构解析

【目的】系统研究印楝素在水溶液中的水解。【方法】硅胶柱层析法和半制备液相色谱法分离纯化w为44.56%的印楝素原药中的印楝素A,采用核磁共振仪和高效液相色谱定性、定量测定分离得到的印楝素A,建立一种检测水样中印楝素残留的高效液相色谱方法。【结果】核磁共振仪和高效液相色谱测得印楝素A的质量分数分别为90.37%和91.82%。当印楝素添加水平为0.1、1.0和5.0 mg·kg~(-1)时,水样中印楝素的平均回收率为92.53%~94.12%,变异系数为0.35%~0.84%,最小检测质量浓度为0.012 mg·L~(-1)。印楝素在p H 4.0~6.0的缓冲溶液中稳定,当p H大于8.0时,印楝素降解加快,降解半衰期从p H 8.0的14.856 h降到p H 10.0的0.033 h。在p H 6.0的缓冲溶液中,25、35、45℃条件下印楝素的降解半衰期分别为24.68、13.69和2.36 d,而在p H 7.0的缓冲溶液中印楝素的降解半衰期分别为9.35、6.51和0.94 d。在p H 2.0的缓冲溶液中分离纯化水解产物得到印楝素A内酯衍生物。【结论】印楝素在碱性环境下极不稳定,而在弱酸性环境中比较稳定。温度对印楝素的降解影响很大,随着温度的升高印楝素降解加快。

Study on hydrolysis kinetics of azadirachtin and structure analysis of hydrolysate

Objective] To study hydrolysis of azadirachtin in water systematically.Method]Azadirachtin A from the 44.56% azadirachtin TC was isolated and purified by silica column chromatography and semi-preparative high performance liquid chromatography (HPLC).The chemical structure and content of isolated azadirachtin A were identified by nulear magnetic resonance (NMR) and HPLC.A method for determining azaditachtin residue in water by HPLC was established.Result]The mass fractions of azadirachtin A were 90.37% and 91.82% detected by NMR and HPLC respectively.When azadirachtin was added with the concentrations of 0.1, 1.0 and 5.0 mg·kg-1, the average recovery rates of azadirachtin from water samples ranged from 92.53% to 94.12%, the variation coefficients ranged from 0.35% to 0.84%, and the minimum detection limit was 0.012 mg·L-1.Azadirachtin was stable in buffer solutions with pH varying from 4.0 to 6.0.When pH was above 8.0, hydrolysis of azadirachtin was accelerated, and the degradation half-life was 14.856 h at pH 8.0 and declined to 0.033 h at pH 10.0.The degration half-lives of azadirachtin in buffer solutions at pH 6.0 were 24.68, 13.69 and 2.36 d under 25, 35 and 45 ℃ temperature respectively, while were 9.35, 6.51 and 0.94 d at pH 7.0.A lactone derivative of azadirachtin was obtained by isolating and purifing hydrolysate in buffer solution at pH 2.0.Conclusion]Azadirachtin is extremely unstable in alkaline environment while relatively stable in weak acid environment.Temperature has a great effect on the degradation of azadirachtin and the degradation accelerates as temperature increases.