白桦脂醇酯类衍生物合成及体外抗氧化活性评价

目的 通过对白桦脂醇不同位点的修饰及进一步抗氧化活性分析，探讨白桦脂醇各修饰位点与抗氧化活性间的关系。方法 以白桦脂醇为起始物，以四氢呋喃（THF）或二甲基甲酰胺（DMF）作溶剂，控制反应温度及酸酐当量，进行酰化、羟基保护、氯铬酸吡啶鎓盐（PCC）氧化、脱保护基等反应合成7个目标化合物，即3,28-二乙酰基白桦脂醇、3,28-二烯丙酰基白桦脂醇、28-乙酰基白桦脂醇、28-烯丙酰基白桦脂醇、3-乙酰基白桦脂醇、3-烯丙酰基白桦脂醇和3-羰基白桦脂醇。采用1,1-二苯基-2-三硝基苯肼（DPPH）法测定目标化合物的体外抗氧化活性。结果 白桦脂醇衍生物的结构通过核磁共振（NMR）图谱、高分辨液质联用（HRLC-MS）综合解释得以验证。DPPH法测试结果显示，白桦脂醇、3-乙酰基或烯丙酰基白桦脂醇及28-乙酰基或烯丙酰基白桦脂醇对DPPH均有一定的清除作用，且呈浓度依赖性，28-乙酰基或烯丙酰基白桦脂醇对DPPH的清除效果优于白桦脂醇及3-乙酰基或烯丙酰基白桦脂醇。在相同条件下，3-羰基白桦脂醇与3,28-双酰基（乙酰基或烯丙酰基）取代白桦脂醇无明显清除DPPH的作用。此外，烯丙酰基修饰的白...

Synthesis and In Vitro Antioxidant Activity Evaluation of Ester Derivatives of Betulin

To explore the relationship between each modification site of betulin and its antioxidantactivity by modifying different sites of betulin and further analyzing its antioxidant activity. Methods Seven targetcompounds，including 3，28-diacetyl betulin，3，28-diallyacyl betulin，28-acetyl betulin，28-allyacyl betulin，3-acetyl betulin， 3-allyacyl betulin and 3-carbonyl betulin were synthesized via acylation， hydroxyl protection，pyridinium chlorochromate （PCC） oxidation， deprotection， and other reactions using betulin as the startingmaterial，as well as tetrahydrofuran （THF） or dimethylformamide （DMF） as the solvent. The reaction temperatureand anhydride equivalent were also controlled. In vitro antioxidant activity of target compounds was determined usingDPPH （1，1-diphenyl-2-trinitrophenylhydrazine）. Results The structure of betulin derivatives were verified throughcomprehensive interpretation of nuclear magnetic resonance （NMR） spectra， and high-resolution liquidchromatography-mass spectrometry （HRLC-MS）. The DPPH trial results showed that betulin，3-acetyl or allyacylbetulin， and 28-acetyl or allyacyl betulin all have a certain scavenging effect on DPPH. The clearance rates ofDPPH increased with increasing concentration of these compounds. The clearance effects of 28-acetyl or allyacylbetulin on DPPH is better than that of betulin and 3-acetyl or allyacyl betulin. There is no significant differencebetween the antioxidant activity of 3-carbonyl betulin and 3， 28-diacetyl or diallyacyl betulin under the same condition. Moreover， in vitro antioxidant activity of allyacyl derivatives is better than that of acetyl derivatives.Conclusion A feasible method for acylation of betulin and protection of hydroxyl functional groups was established.28-allyacyl betulin exhibits slightly higher in vitro antioxidant activity than betulin and other betulin derivatives. Itwas suggested that introduction of an eletron-withdrawing group at the 28-position of betulin may enhance itsantioxidant effect.