印楝素水解动力学研究及水解产物结构解析

Study on hydrolysis kinetics of azadirachtin and structure analysis of hydrolysate

【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。

【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.