Co-innovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China.
Department of Food Science and Technology, College of Light Industry and Food Engineering, Nanjing Forestry University, Nanjing 210037, China.
J Agric Food Chem. 2021 Dec 1;69(47):14270-14277. doi: 10.1021/acs.jafc.1c04937. Epub 2021 Nov 19.
4'--Methylpyridoxine (MPN) and MPN-5'-glucoside (MPNG) are collectively known as ginkgotoxin, which are the main toxic ingredients of excessive consumption of seeds. Water extraction is the generally adopted sample preparation method for high-performance liquid chromatography determination of ginkgotoxin. However, endogenous enzymes such as glycosidases in seeds can hydrolyze MPNG to MPN in the process of water extraction, which will result in the measured contents of MPN and MPNG but not their natural contents in seeds. In this work, inhibitors for the endogenous enzymes were first screened, and it was found that silver fluoride could effectively inhibit endogenous enzymes such as glucosidase and phosphatase. The optimized concentration of silver fluoride was 25 mmol/L, which could effectively inhibit the endogenous enzymes for more than 60 h. A new sample preparation method based on water extraction with 25 mmol/L silver fluoride addition was thus developed. This method was employed to determine the native contents of MPN and MPNG in the exotesta and kernel of five seed cultivars. The result showed that the contents of MPNG in the exotesta and kernel of five cultivars were significantly higher than those of MPN. MPNG was present at high content in raw seeds, which was the main form of ginkgotoxin in seeds. The method established in this work is simple and effective and can be used to accurately quantify the native contents of MPN and MPNG.
4'-甲氧基吡啶（MPN）和 MPN-5'-葡萄糖苷（MPNG）统称为银杏毒素，是过量食用白果种子的主要有毒成分。水提是高效液相色谱法测定银杏毒素时通常采用的样品制备方法。然而，种子中的内源性酶，如糖苷酶，在水提过程中会将 MPNG 水解为 MPN，这将导致测定的 MPN 和 MPNG 的含量，但不是种子中它们的天然含量。在这项工作中，首先筛选了内源性酶的抑制剂，发现氟化银可以有效地抑制糖苷酶和磷酸酶等内源性酶。优化的氟化银浓度为 25mmol/L，可有效抑制内源性酶 60 小时以上。因此，开发了一种基于添加 25mmol/L 氟化银的水提的新样品制备方法。该方法用于测定五种白果外种皮和种仁中 MPN 和 MPNG 的天然含量。结果表明，五种品种外种皮和种仁中 MPNG 的含量明显高于 MPN。MPNG 在生种子中含量较高，是种子中银杏毒素的主要形式。本工作建立的方法简单有效，可用于准确测定 MPN 和 MPNG 的天然含量。
