山梨酸钾的烷基化潜力。

Alkylating potential of potassium sorbate.

作者信息

Pérez-Prior M Teresa, Manso José A, García-Santos M Del Pilar, Calle Emilio, Casado Julio

机构信息

Departamento de Química física, Universidad de Salamanca, E-37008 Salamanca, Spain.

出版信息

J Agric Food Chem. 2005 Dec 28;53(26):10244-7. doi: 10.1021/jf052152p.

DOI:10.1021/jf052152p

PMID:16366722

Abstract

A kinetic study of the alkylating potential of potassium sorbate (S)-a food preservative used worldwide-in 7:3 water/dioxane medium was performed. The following conclusions were drawn: (i) Potassium sorbate shows alkylating activity on the nucleophile 4-(p-nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilic characteristics similar to those of DNA bases, (ii) The NBP alkylation reaction complies with the rate equation r = k(alk)[H+][S][NBP]/(K(a) + [H+]), K(a) being the sorbic acid dissociation constant and k(alk) the rate constant of NBP alkylation by the undissociated acid. In the range of pH 5-6, the alkylation time ranges between 18 days (pH 5.2) and >1 month (pH > or = 6). (iii) NBP alkylation occurs through a reaction with deltaH# = 78 kJ mol(-1), which is much higher than those of NBP alkylation by stronger alkylating agents. (iv) The absorption coefficient of the sorbate-NBP adduct was determined to be epsilon = 204 M(-1) cm(-1) (lambda = 580 nm), this value being rationalized in terms of the adduct structure. (v) The results can help to establish suitable expiration times for products preserved with potassium sorbate.

摘要

对全球范围内使用的食品防腐剂山梨酸钾（S）在7:3水/二氧六环介质中的烷基化潜力进行了动力学研究。得出了以下结论：（i）山梨酸钾对亲核试剂4-（对硝基苄基）吡啶（NBP）具有烷基化活性，NBP是一种用于捕获具有与DNA碱基相似亲核特性的烷基化剂的物质；（ii）NBP烷基化反应符合速率方程r = k(alk)[H⁺][S][NBP]/(K(a) + [H⁺])，其中K(a)是山梨酸的解离常数，k(alk)是未解离酸对NBP进行烷基化的速率常数。在pH 5 - 6范围内，烷基化时间在18天（pH 5.2）至>1个月（pH≥6）之间。（iii）NBP烷基化通过ΔH# = 78 kJ mol⁻¹的反应发生，该值远高于更强烷基化剂对NBP烷基化的反应热。（iv）山梨酸酯 - NBP加合物的吸收系数测定为ε = 204 M⁻¹ cm⁻¹（λ = 580 nm），该值根据加合物结构得到了合理的解释。（v）这些结果有助于确定用山梨酸钾保存的产品的合适保质期。