酚羟基保护法合成硬脂酰单宁酸酯及其抗氧化性能评价

Synthesis and Antioxidant Acticity of Stearoyl Tannic Acid Ester Based on Hydroxyl Protection

为解决单宁酸（TA）亲水性强亲油性弱的问题,以单宁酸为原料,利用苄基溴将单宁酸的部分酚羟基保护后得到单宁酸苄基醚（TBE）,再以硬脂酸酐为酰基化试剂,吡啶为催化剂,N2保护下反应,引入长链脂肪烃;最后在弱酸条件下将苄基水解脱去,制得硬脂酰单宁酸酯（C18-TA）。采用均匀实验优化合成条件,傅里叶红外光谱（FT-IR）、紫外光谱（UV）、核磁共振（1H NMR）表征了C18-TA的结构,并通过C18-TA清除·DPPH的能力和抗油脂氧化能力评价其抗氧化性能。结果表明：优化最佳合成条件为单宁酸1 g,硬脂酸0.6 g,吡啶1.5 mL,反应温度80℃,回流时间265 min,得到的C18-TA产率可达87.98%。使用酚羟基保护法制得的C18-TA不仅改善了单宁酸的表面活性,而且保留了单宁酸中多数的酚羟基,抗氧化能力明显高于单宁酸和丁基羟基茴香醚（BHA）,质量浓度为0.050.25 g/L,对·DPPH的清除率为91.96%97.39%;对亚麻籽油的抗氧化值（POV）升高缓慢,030 d为3.8217.72 mmol/kg。

In order to solve the high water-solubility and low oil-solubility of tannic acid（ TA）, stearoyl tannic acid ester （C18- TA） as a kind of natural antioxidant was synthesized from tannic acid and stearic anhydride through three steps in the present study. At first, the phenolic hydroxyl of tannic acid was partially protected by benzyl bromide, then the long chain fatty hydrocarbyl was introduced with stearic anhydride as acetylating reagent, pyridine as catalyst and N2 as shielding gas. At last, benzyl group was removed in weak acid and C1s-TA was obtained. The synthetic conditions were optimized through uniform design. The chemical structure of CIs-TA was characterized by FT-IR, UV and 1H NMR. The antioxidant activity was assayed by · DPPH scavenging and peroxide value （POV） of linseed oil. The results showed that the optimized conditions were the dosage of tannin 1 g, stearic acid 0.6 g, pyridine 1.5 mL, reaction temperature 80 ℃, and refluent time 265 min. Under the optimized conditions, the yield of C18-TA reached 87.98%. The C18-TA synthesized by hydroxyl protection owned much hydroxyl and excellent surfactivity. The antioxidant activity of CIs-TA was higher than tannic acid and butylated hydroxyanisole （BHA）. The · DPPH scavenging rate of C18-TA reached 91.96% - 97.39% at the mass concentration of 0.05 - 0.25 g/L. The POVs of linseed oil increased slowly and were 3.82 - 17.72 mmol/kg in 0 - 30 d.